What is a segmentation fault? Is it different in C and C++? How are segmentation faults and dangling pointers related?

What is a segmentation fault?

The following code receives seg fault on line 2:

    char *str = &quot;string&quot;;
    str[0] = &#39;z&#39;;  // could be also written as *str = &#39;z&#39;
    printf(&quot;%s\n&quot;, str);

While this works perfectly well:

    char str[] = &quot;string&quot;;
    str[0] = &#39;z&#39;;
    printf(&quot;%s\n&quot;, str);

Tested with MSVC and GCC.

Why do I get a segmentation fault when writing to a &quot;char *s&quot; initialized with a string literal, but not &quot;char s[]&quot;?

What does the &quot;bus error&quot; message mean, and how does it differ from a [segmentation fault][1]?

  [1]: https://en.wikipedia.org/wiki/Segmentation_fault


What is a bus error? Is it different from a segmentation fault?

I&#39;ve been reading the other posts on tracking down the reasons for getting a `SIGSEGV` in an Android app. I plan to scour my app for possible NullPointers related to Canvas use, but my `SIGSEGV` barfs up a different memory address each time. Plus I&#39;ve seen `code=1` and `code=2`. If the memory address was `0x00000000`, I&#39;d have a clue it is a NullPointer.

The last one I got was a `code=2`:

    A/libc(4969): Fatal signal 11 (SIGSEGV) at 0x42a637d9 (code=2)

Any suggestions on how to track this down?

I have a suspect, but I&#39;m not keen on experimenting with it yet. My app uses the OSMDroid API for offline mapping. The OverlayItem class represents markers/nodes on the map. I have a Service that collects data via the network to populate the OverlayItem which are then displayed on the map. In an effort to simplify my design, I extended OverlayItem into my own NodeOverlayItem class, which includes some addition attributes I use in the UI Activity and in the Service. This gave me a single point of Item information for the UI and Service. I used Intents to broadcast to the Activity to refresh the UI map when something changed. The Activity binds to the Service and there&#39;s a Service method to get the list of NodeOverlayItem&#39;s. I think it might be the OSMDroid API&#39;s use of OverlayItem, and my Service updating node information at the same time. (a concurrency issue)

As I write this I think that&#39;s really the problem. The headache isn&#39;t splitting out the Node and OverlayItem from NodeOverlayItem, it&#39;s that the Activity will need some data from the Node, that the Service holds. Plus when the Activity is created (onResume, etc...) the OverlayItem objects will need to be re-created from the Node data that the Service has been maintaining while the Activity was away. e.g. You start the app, the Service collects data, the UI displays it, you go to Home, then back to the app, the Activity will need to pull and re-create the OverlayItem&#39;s from the latest Service node data.

I know this isn&#39;t a great or clear questions. It&#39;s like all my SO questions are niche or obscure. If anyone has a suggestion on how to interpret those `SIGSEGV` errors, it would be greatly appreciated!

**UPDATE**
Here&#39;s the latest crash captured during a debug session. I have 3 of these devices being used for testing and they don&#39;t all crash reliably when I&#39;m developing and testing. I included a bit extra just so the GC logging could be noted. You can see the problem is probably not related to memory exhaustion.

    03-03 02:02:38.328: I/CommService(7477): Received packet from: 192.168.1.102
    03-03 02:02:38.328: I/CommService(7477): Already processed this packet. It&#39;s a re-broadcast from another node, or from myself. It&#39;s not a repeat broadcast though.
    03-03 02:02:38.406: D/CommService(7477): Checking OLSRd info...
    03-03 02:02:38.460: D/CommService(7477): Monitoring nodes...
    03-03 02:02:38.515: D/dalvikvm(7477): GC_CONCURRENT freed 2050K, 16% free 17151K/20359K, paused 3ms+6ms
    03-03 02:02:38.515: I/CommService(7477): Received packet from: 192.168.1.102
    03-03 02:02:38.515: D/CommService(7477): Forwarding packet (4f68802cf10684a83ac4936ebb3c934d) along to other nodes.
    03-03 02:02:38.609: I/CommService(7477): Received packet from: 192.168.1.100
    03-03 02:02:38.609: D/CommService(7477): Forwarding packet (e4bc81e91ec92d06f83e03068f52ab4) along to other nodes.
    03-03 02:02:38.609: D/CommService(7477): Already processed this packet: 4204a5b27745ffe5e4f8458e227044bf
    03-03 02:02:38.609: A/libc(7477): Fatal signal 11 (SIGSEGV) at 0x68f52abc (code=1)
    03-03 02:02:38.914: I/DEBUG(4008): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
    03-03 02:02:38.914: I/DEBUG(4008): Build fingerprint: &#39;Lenovo/IdeaTab_A1107/A1107:4.0.4/MR1/eng.user.20120719.150703:user/release-keys&#39;
    03-03 02:02:38.914: I/DEBUG(4008): pid: 7477, tid: 7712  &gt;&gt;&gt; com.test.testm &lt;&lt;&lt;
    03-03 02:02:38.914: I/DEBUG(4008): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 68f52abc
    03-03 02:02:38.914: I/DEBUG(4008):  r0 68f52ab4  r1 412ef268  r2 4d9c3bf4  r3 412ef268
    03-03 02:02:38.914: I/DEBUG(4008):  r4 001ad8f8  r5 4d9c3bf4  r6 412ef268  r7 4c479df8
    03-03 02:02:38.914: I/DEBUG(4008):  r8 4d9c3c0c  r9 4c479dec  10 46cf260a  fp 4d9c3c24
    03-03 02:02:38.914: I/DEBUG(4008):  ip 40262a04  sp 4d9c3bc8  lr 402d01dd  pc 402d0182  cpsr 00000030
    03-03 02:02:38.914: I/DEBUG(4008):  d0  00000001000c0102  d1  3a22364574614c7d
    03-03 02:02:38.914: I/DEBUG(4008):  d2  403fc0000000007d  d3  363737343433350a
    03-03 02:02:38.914: I/DEBUG(4008):  d4  49544341223a2273  d5  6f6567222c224556
    03-03 02:02:38.914: I/DEBUG(4008):  d6  3a223645676e6f4c  d7  000000013835372d
    03-03 02:02:38.914: I/DEBUG(4008):  d8  0000000000000000  d9  4040000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d10 0000000000000000  d11 4040000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d12 4040000000000000  d13 0000000000000021
    03-03 02:02:38.914: I/DEBUG(4008):  d14 0000000000000000  d15 0000000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d16 3fe62e42fefa39ef  d17 3ff0000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d18 3fe62e42fee00000  d19 0000000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d20 0000000000000000  d21 3ff0000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d22 4028000000000000  d23 3ff0000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d24 0000000000000000  d25 3ff0000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d26 0000000000000000  d27 c028000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d28 0000000000000000  d29 3ff0000000000000
    03-03 02:02:38.914: I/DEBUG(4008):  d30 3ff0000000000000  d31 3fecccccb5c28f6e
    03-03 02:02:38.914: I/DEBUG(4008):  scr 60000013
    03-03 02:02:39.046: I/DEBUG(4008):          #00  pc 0006b182  /system/lib/libcrypto.so (EVP_DigestFinal_ex)
    03-03 02:02:39.046: I/DEBUG(4008):          #01  pc 0006b1d8  /system/lib/libcrypto.so (EVP_DigestFinal)
    03-03 02:02:39.054: I/DEBUG(4008):          #02  pc 0001f814  /system/lib/libnativehelper.so
    03-03 02:02:39.054: I/DEBUG(4008):          #03  pc 0001ec30  /system/lib/libdvm.so (dvmPlatformInvoke)
    03-03 02:02:39.054: I/DEBUG(4008):          #04  pc 00058c70  /system/lib/libdvm.so (_Z16dvmCallJNIMethodPKjP6JValuePK6MethodP6Thread)
    03-03 02:02:39.054: I/DEBUG(4008): code around pc:
    03-03 02:02:39.054: I/DEBUG(4008): 402d0160 0003151e 4604b570 f7ff460d 4620ff81  ....p..F.F.... F
    03-03 02:02:39.054: I/DEBUG(4008): 402d0170 f7ff4629 bd70ff93 4604b570 460e6800  )F....p.p..F.h.F
    03-03 02:02:39.054: I/DEBUG(4008): 402d0180 68834615 dd062b40 21fa4810 44784a10  .F.h@+...H.!.JxD
    03-03 02:02:39.054: I/DEBUG(4008): 402d0190 f7c8447a 6821f80f 698a4620 47904631  zD....!h F.i1F.G
    03-03 02:02:39.054: I/DEBUG(4008): 402d01a0 b1154606 68836820 6822602b b12b6a13  .F.. h.h+`&quot;h.j+.
    03-03 02:02:39.054: I/DEBUG(4008): code around lr:
    03-03 02:02:39.054: I/DEBUG(4008): 402d01bc 68e06821 21006c4a ea0af7c4 bd704630  !h.hJl.!....0Fp.
    03-03 02:02:39.054: I/DEBUG(4008): 402d01cc 00031492 000314b5 4604b570 ffcef7ff  ........p..F....
    03-03 02:02:39.054: I/DEBUG(4008): 402d01dc 46204605 ff12f7ff bd704628 4604b573  .F F....(Fp.s..F
    03-03 02:02:39.054: I/DEBUG(4008): 402d01ec 2102460d fb36f002 42ab6823 b123d020  .F.!..6.#h.B .#.
    03-03 02:02:39.054: I/DEBUG(4008): 402d01fc b1136c5b f7c868e0 68a0fccf 05c26025  [l...h.....h%`..
    03-03 02:02:39.054: I/DEBUG(4008): memory map around addr 68f52abc:
    03-03 02:02:39.054: I/DEBUG(4008): 4d8c5000-4d9c4000 
    03-03 02:02:39.054: I/DEBUG(4008): (no map for address)
    03-03 02:02:39.054: I/DEBUG(4008): b0001000-b0009000 /system/bin/linker
    03-03 02:02:39.054: I/DEBUG(4008): stack:
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b88  408d1f90  /system/lib/libdvm.so
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b8c  412ef258  /dev/ashmem/dalvik-heap (deleted)
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b90  00000001  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b94  408d6c58  /system/lib/libdvm.so
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b98  408d6fa8  /system/lib/libdvm.so
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3b9c  4c479dec  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3ba0  46cf260a  /system/framework/core.odex
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3ba4  408735e7  /system/lib/libdvm.so
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3ba8  412ef258  /dev/ashmem/dalvik-heap (deleted)
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bac  002bf070  [heap]
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bb0  412ef258  /dev/ashmem/dalvik-heap (deleted)
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bb4  00000000  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bb8  412ef268  /dev/ashmem/dalvik-heap (deleted)
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bbc  00000000  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bc0  df0027ad  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bc4  00000000  
    03-03 02:02:39.054: I/DEBUG(4008): #00 4d9c3bc8  001ad8f8  [heap]
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bcc  002ae0b8  [heap]
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bd0  00000004  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bd4  402d01dd  /system/lib/libcrypto.so
    03-03 02:02:39.054: I/DEBUG(4008): #01 4d9c3bd8  001ad8f8  [heap]
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3bdc  002ae0b8  [heap]
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3be0  00000004  
    03-03 02:02:39.054: I/DEBUG(4008):     4d9c3be4  4024e817  /system/lib/libnativehelper.so
    03-03 02:02:39.406: D/CommService(7477): Checking OLSRd info...
    03-03 02:02:39.500: D/CommService(7477): Monitoring nodes...
    03-03 02:02:39.500: D/dalvikvm(7477): GC_FOR_ALLOC freed 2073K, 16% free 17118K/20359K, paused 51ms
    03-03 02:02:39.632: D/dalvikvm(7477): GC_CONCURRENT freed 1998K, 16% free 17162K/20359K, paused 2ms+4ms
    03-03 02:02:40.406: D/CommService(7477): Checking OLSRd info...
    03-03 02:02:40.445: D/CommService(7477): Monitoring nodes...
    03-03 02:02:40.562: D/dalvikvm(7477): GC_CONCURRENT freed 2045K, 16% free 17158K/20359K, paused 3ms+4ms
    03-03 02:02:41.406: D/CommService(7477): Checking OLSRd info...
    03-03 02:02:41.445: D/CommService(7477): Monitoring nodes...
    03-03 02:02:41.531: D/dalvikvm(7477): GC_CONCURRENT freed 2045K, 16% free 17154K/20359K, paused 3ms+12ms
    03-03 02:02:42.406: D/CommService(7477): Checking OLSRd info...
    03-03 02:02:42.445: D/CommService(7477): Monitoring nodes...
    03-03 02:02:42.507: D/dalvikvm(7477): GC_CONCURRENT freed 2068K, 16% free 17128K/20359K, paused 3ms+4ms
    03-03 02:02:42.679: D/dalvikvm(7477): GC_CONCURRENT freed 2006K, 16% free 17161K/20359K, paused 2ms+12ms
    03-03 02:02:43.140: I/BootReceiver(1236): Copying /data/tombstones/tombstone_05 to DropBox (SYSTEM_TOMBSTONE)
    03-03 02:02:43.210: D/dalvikvm(1236): GC_FOR_ALLOC freed 912K, 17% free 10207K/12295K, paused 62ms
    03-03 02:02:43.265: D/dalvikvm(1236): GC_FOR_ALLOC freed 243K, 16% free 10374K/12295K, paused 49ms
    03-03 02:02:43.265: I/dalvikvm-heap(1236): Grow heap (frag case) to 10.507MB for 196628-byte allocation



Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

How does one determine where the mistake is in the code that causes a [segmentation fault](https://stackoverflow.com/questions/2346806/what-is-a-segmentation-fault)?

Can my compiler (`gcc`) show the location of the fault in the program?

Determine the line of code that causes a segmentation fault?

I&#39;m getting the error ...

&gt;Command failed due to signal: Segmentation fault: 11

... when trying to compile my Swift app. I&#39;m using Xcode 6.1, trying to build for an iPhone 5 on iOS 8.1.

**My Code**

    import UIKit
    
    class ViewController: UIViewController {
    
        @IBOutlet weak var username: UITextField!
        @IBAction func signIn(sender: AnyObject) {
            
            PFUser.logInWithUsernameInBackground(username.text, password:&quot;mypass&quot;) {
                (user: PFUser!, error: NSError!) -&gt; Void in
                if user != nil {
                    println(&quot;Logged In&quot;)
                } else {
                    
                    func myMethod() {
                        var user = PFUser()
                        user.username = username.text
                        user.password = &quot; &quot;
                        user.signUpInBackgroundWithBlock {
                            (succeeded: Bool!, error: NSError!) -&gt; Void in
                            if error == nil {
                                // Hooray! Let them use the app now.
                            } else {
                                    println(&quot;Signed Up&quot;)
                            }
                        }
                    }
                     
                 println(error)
                }
            }
        }
        override func viewDidLoad() {
            super.viewDidLoad()
            // Do any additional setup after loading the view, typically from a nib.
            Parse.setApplicationId(&quot;key here&quot;)
        }

        override func didReceiveMemoryWarning() {
            super.didReceiveMemoryWarning()
            // Dispose of any resources that can be recreated.
        }
    }

**And the error text!**

    CompileSwift normal arm64 /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/ViewController.swift
        cd /Users/Alec/Desktop/Re-Chat/Re-Chat
        /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/ViewController.swift /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/AppDelegate.swift -target arm64-apple-ios8.0 -Xllvm -aarch64-use-tbi -target-cpu cyclone -target-abi darwinpcs -sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk -I /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos -F /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos -F /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat -g -import-objc-header /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/Re-Chat-Bridging-Header.h -module-cache-path /Users/Alec/Library/Developer/Xcode/DerivedData/ModuleCache -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-generated-files.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-own-target-headers.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-all-target-headers.hmap -Xcc -iquote -Xcc /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-project-headers.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos/include -Xcc -I/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/DerivedSources/arm64 -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/DerivedSources -Xcc -DDEBUG=1 -emit-module-doc-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController~partial.swiftdoc -Onone -module-name Re_Chat -emit-module-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController~partial.swiftmodule -serialize-diagnostics-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.dia -emit-dependencies-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.d -o /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.o
    0  swift                    0x0000000108145a68 llvm::sys::PrintStackTrace(__sFILE*) + 40
    1  swift                    0x0000000108145f54 SignalHandler(int) + 452
    2  libsystem_platform.dylib 0x00007fff86631f1a _sigtramp + 26
    3  libsystem_platform.dylib 0x00007fd0ac1eb010 _sigtramp + 633049360
    4  swift                    0x00000001075d4517 swift::Lowering::SILGenFunction::emitClosureValue(swift::SILLocation, swift::SILDeclRef, llvm::ArrayRef&lt;swift::Substitution&gt;, swift::AnyFunctionRef) + 1303
    5  swift                    0x00000001075c599e swift::Lowering::SILGenFunction::visitFuncDecl(swift::FuncDecl*) + 190
    6  swift                    0x000000010760987c swift::Lowering::SILGenFunction::visitBraceStmt(swift::BraceStmt*) + 380
    7  swift                    0x000000010760c8e8 swift::ASTVisitor&lt;swift::Lowering::SILGenFunction, void, void, void, void, void, void&gt;::visit(swift::Stmt*) + 152
    8  swift                    0x000000010760a0a5 swift::Lowering::SILGenFunction::visitIfStmt(swift::IfStmt*) + 757
    9  swift                    0x000000010760c8f6 swift::ASTVisitor&lt;swift::Lowering::SILGenFunction, void, void, void, void, void, void&gt;::visit(swift::Stmt*) + 166
    10 swift                    0x00000001076097e8 swift::Lowering::SILGenFunction::visitBraceStmt(swift::BraceStmt*) + 232
    11 swift                    0x000000010760c8e8 swift::ASTVisitor&lt;swift::Lowering::SILGenFunction, void, void, void, void, void, void&gt;::visit(swift::Stmt*) + 152
    12 swift                    0x00000001075d52dd swift::Lowering::SILGenFunction::emitClosure(swift::AbstractClosureExpr*) + 205
    13 swift                    0x00000001075b4234 swift::Lowering::SILGenModule::emitClosure(swift::AbstractClosureExpr*) + 196
    14 swift                    0x00000001075eef71 (anonymous namespace)::RValueEmitter::visitAbstractClosureExpr(swift::AbstractClosureExpr*, swift::Lowering::SGFContext) + 97
    15 swift                    0x00000001075e1866 swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 2870
    16 swift                    0x00000001075e24da swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 6058
    17 swift                    0x00000001075cfa0b swift::Lowering::SILGenFunction::emitExprInto(swift::Expr*, swift::Lowering::Initialization*) + 235
    18 swift                    0x00000001075ae824 swift::Lowering::RValueSource::materialize(swift::Lowering::SILGenFunction&amp;) &amp;&amp; + 196
    19 swift                    0x0000000107604a69 swift::Lowering::RValueSource::materialize(swift::Lowering::SILGenFunction&amp;, swift::Lowering::AbstractionPattern, swift::SILType) &amp;&amp; + 233
    20 swift                    0x00000001075f371c swift::Lowering::SILGenFunction::emitInjectOptionalValueInto(swift::SILLocation, swift::Lowering::RValueSource&amp;&amp;, swift::SILValue, swift::Lowering::TypeLowering const&amp;) + 268
    21 swift                    0x00000001075e9b8d swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 36445
    22 swift                    0x00000001075e3e2b swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 12539
    23 swift                    0x00000001075e202b swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 4859
    24 swift                    0x00000001075cfab6 swift::Lowering::SILGenFunction::emitRValue(swift::Expr*, swift::Lowering::SGFContext) + 22
    25 swift                    0x00000001075bffc4 (anonymous namespace)::ArgEmitter::emitExpanded(swift::Lowering::RValueSource&amp;&amp;, swift::Lowering::AbstractionPattern) + 836
    26 swift                    0x00000001075bf582 (anonymous namespace)::ArgEmitter::emit(swift::Lowering::RValueSource&amp;&amp;, swift::Lowering::AbstractionPattern) + 98
    27 swift                    0x00000001075b7ff8 (anonymous namespace)::CallEmission::apply(swift::Lowering::SGFContext) + 1128
    28 swift                    0x00000001075b751a swift::Lowering::SILGenFunction::emitApplyExpr(swift::ApplyExpr*, swift::Lowering::SGFContext) + 58
    29 swift                    0x00000001075e0d81 swift::ASTVisitor&lt;(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext&gt;::visit(swift::Expr*, swift::Lowering::SGFContext) + 81
    30 swift                    0x00000001075ea00d swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 237
    31 swift                    0x0000000107609829 swift::Lowering::SILGenFunction::visitBraceStmt(swift::BraceStmt*) + 297
    32 swift                    0x000000010760c8e8 swift::ASTVisitor&lt;swift::Lowering::SILGenFunction, void, void, void, void, void, void&gt;::visit(swift::Stmt*) + 152
    33 swift                    0x00000001075d4ee0 swift::Lowering::SILGenFunction::emitFunction(swift::FuncDecl*) + 256
    34 swift                    0x00000001075b3659 swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 233
    35 swift                    0x00000001075cea93 swift::ASTVisitor&lt;SILGenType, void, void, void, void, void, void&gt;::visit(swift::Decl*) + 355
    36 swift                    0x00000001075cd7eb SILGenType::emitType() + 203
    37 swift                    0x00000001075c85ae swift::Lowering::SILGenModule::visitNominalTypeDecl(swift::NominalTypeDecl*) + 30
    38 swift                    0x00000001075b555b swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*, unsigned int) + 395
    39 swift                    0x00000001075b581a swift::SILModule::constructSIL(swift::Module*, swift::SourceFile*, swift::Optional&lt;unsigned int&gt;) + 314
    40 swift                    0x00000001075b5968 swift::performSILGeneration(swift::SourceFile&amp;, swift::Optional&lt;unsigned int&gt;) + 72
    41 swift                    0x000000010748be18 frontend_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) + 3432
    42 swift                    0x000000010748996d main + 1677
    43 libdyld.dylib            0x00007fff8aa4c5c9 start + 1
    Stack dump:
    0.	Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/ViewController.swift /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/AppDelegate.swift -target arm64-apple-ios8.0 -Xllvm -aarch64-use-tbi -target-cpu cyclone -target-abi darwinpcs -sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk -I /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos -F /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos -F /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat -g -import-objc-header /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/Re-Chat-Bridging-Header.h -module-cache-path /Users/Alec/Library/Developer/Xcode/DerivedData/ModuleCache -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-generated-files.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-own-target-headers.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-all-target-headers.hmap -Xcc -iquote -Xcc /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Re-Chat-project-headers.hmap -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Products/Debug-iphoneos/include -Xcc -I/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/DerivedSources/arm64 -Xcc -I/Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/DerivedSources -Xcc -DDEBUG=1 -emit-module-doc-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController~partial.swiftdoc -Onone -module-name Re_Chat -emit-module-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController~partial.swiftmodule -serialize-diagnostics-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.dia -emit-dependencies-path /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.d -o /Users/Alec/Library/Developer/Xcode/DerivedData/Re-Chat-awwdkmqavitiqkcdsphwnhzhzzfb/Build/Intermediates/Re-Chat.build/Debug-iphoneos/Re-Chat.build/Objects-normal/arm64/ViewController.o 
    1.	While emitting SIL for &#39;signIn&#39; at /Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/ViewController.swift:14:15
    2.	While silgen closureexpr SIL function @_TFFC7Re_Chat14ViewController6signInFS0_FPSs9AnyObject_T_U_FTGSQCSo6PFUser_GSQCSo7NSError__T_ for expression at [/Users/Alec/Desktop/Re-Chat/Re-Chat/Re-Chat/ViewController.swift:16:80 - line:45:9] RangeText=&quot;{
                (user: PFUser!, error: NSError!) -&gt; Void in
                if user != nil {
                    // Do stuff after successful login.
                    
                    println(&quot;Logged In&quot;)
                } else {
                    
                    func myMethod() {
                        var user = PFUser()
                        user.username = username.text
                        user.password = &quot;&quot;
                        // other fields can be set just like with PFObject
                     
                        
                        user.signUpInBackgroundWithBlock {
                            (succeeded: Bool!, error: NSError!) -&gt; Void in
                            if error == nil {
                                // Hooray! Let them use the app now.
                            } else {
                                    println(&quot;Signed Up&quot;)
                            }
                        }
                    }
                    
                    
                 println(&quot;error&quot;)
                }
            }&quot;

Command failed due to signal: Segmentation fault: 11

The following code gives me a segmentation fault when run on a 2Gb machine, but works on a 4GB machine.


    int main()
    {
       int c[1000000];
       cout &lt;&lt; &quot;done\n&quot;;
       return 0;
    }

The size of the array is just 4Mb. Is there a limit on the size of an array that can be used in c++?



Segmentation fault on large array sizes

I came across the following C puzzle:

   Q: Why does the following program segfault on IA-64, but work fine on IA-32?

    
      int main()
      {
          int* p;
          p = (int*)malloc(sizeof(int));
          *p = 10;
          return 0;
      }

I know that the size of `int` on a 64 bit machine may not be the same as the size of a pointer (`int` could be 32 bits and pointer could be 64 bits). But I am not sure how this relates to the above program.
Any ideas?



Why does this code segfault on 64-bit architecture but work fine on 32-bit?

I am writing a cross-platform C++ program for Windows and Unix. On the Window side, the code will compile and execute no problem. On the Unix side, it will compile however when I try to run it, I get a segmentation fault. My initial hunch is that there is a problem with pointers.

**What are good methodologies to find and fix segmentation fault errors?**


Fixing Segmentation faults in C++

I am implementing Kosaraju&#39;s Strong Connected Component(SCC) graph search algorithm in Python.

The program runs great on small data set, but when I run it on a super-large graph (more than 800,000 nodes), it says &quot;Segmentation Fault&quot;.

What might be the cause of it? Thank you!

_____
Additional Info:
First I got this Error when running on the super-large data set:

    &quot;RuntimeError: maximum recursion depth exceeded in cmp&quot;
Then  I reset the recursion limit using

    sys.setrecursionlimit(50000)

but got a &#39;Segmentation fault&#39;

Believe me it&#39;s not a infinite loop, it runs correct on relatively smaller data. It is possible the program exhausted the resources?

What causes a Python segmentation fault?

What is `SEGV_MAPERR`, why does it always come up with `SIGSEGV`?

What is SEGV_MAPERR?

Following [a previous question of mine][1], most comments say &quot;just don&#39;t, you are in a limbo state, you have to kill everything and start over&quot;. [There is also a &quot;safeish&quot; workaround][2].

What I fail to understand is ***why*** a segmentation fault is inherently nonrecoverable.

The moment in which writing to protected memory is caught - otherwise, the `SIGSEGV` would not be sent.

If the moment of writing to protected memory can be caught, I don&#39;t see why - in theory - it can&#39;t be reverted, at some low level, and have the SIGSEGV converted to a standard software exception.

Please explain why after a segmentation fault the program is in an undetermined state, as very obviously, the fault is thrown *before* memory was actually changed (I am probably wrong and don&#39;t see why). Had it been thrown after, one could create a program that changes protected memory, one byte at a time, getting segmentation faults, and eventually reprogramming the kernel - a security risk that is not present, as we can see the world still stands.

 1. When exactly does a segmentation fault happen (= when is `SIGSEGV` sent)?
 2. Why is the process in an undefined behavior state after that point?
 3. Why is it not recoverable?
 4. Why does [this solution][2] avoid that unrecoverable state? Does it even?



  [1]: https://stackoverflow.com/q/70234212/913098
  [2]: https://stackoverflow.com/a/12824168/913098




Why is a segmentation fault not recoverable?

I need to catch segmentation fault in third party library cleanup operations. This happens sometimes just before my program exits, and I cannot fix the real reason of this. In Windows programming I could do this with __try - __catch. Is there cross-platform or platform-specific way to do the same? I need this in Linux, gcc.

How to catch segmentation fault in Linux?

I&#39;m moving [a project][1] to the new Android Native Development Kit (i.e. JNI) and I&#39;d like to catch SIGSEGV, should it occur (possibly also SIGILL, SIGABRT, SIGFPE) in order to present a nice crash reporting dialog, instead of (or before) what currently happens: the immediate unceremonious death of the process and possibly some attempt by the OS to restart it. (&lt;b&gt;Edit:&lt;/b&gt; The JVM/Dalvik VM catches the signal and logs a stack trace and other useful information; I just want to offer the user the option to email that info to me really.) 

The situation is: a large body of C code which I didn&#39;t write does most of the work in this application (all the game logic) and although it&#39;s well-tested on numerous other platforms, it&#39;s entirely possible that I, in my Android port, will feed it garbage and cause a crash in native code, so I want the crash dumps (both native and Java) that currently show up in the Android log (I guess it would be stderr in a non-Android situation). I&#39;m free to modify both C and Java code arbitrarily, although the callbacks (both going in and coming out of JNI) number about 40 and obviously, bonus points for small diffs.

I&#39;ve heard of the signal chaining library in J2SE, libjsig.so, and if I could safely install a signal handler like that on Android, that would solve the catching part of my question, but I see no such library for Android/Dalvik.


  [1]: http://chris.boyle.name/projects/android-puzzles

How can I catch SIGSEGV (segmentation fault) and get a stack trace under JNI on Android?

I need to know the root cause of the segmentation fault (SIGSEGV), and how to handle it.

What causes a SIGSEGV

How can I debug a Python segmentation fault?

We are trying to run our python code on SuSE 12.3. We get reproducible segmentation faults. The python code has been working on other platforms without segmentation faults, for years.

We only code Python, no C extension ....

What is the best way to debug this? I know a bit ansi c, but that was ten years ago ....

Python 2.7.5

**Update**

The segmentation fault happens on interpreter shutdown.

I can run the script several times:

    python -m pdb myscript.py arg1 arg1
    continue
    run
    continue
    run
    
But the segmentation faults happen, if I leave the pdb with ctrl-d.


**Update 2**

I now try to debug it with gdb:

    gdb 
    &gt; file python
    &gt; run myscript.py arg1 arg2
    Program received signal SIGSEGV, Segmentation fault.
    [Switching to Thread 0x7fffefbe2700 (LWP 15483)]
    0x00007ffff7aef93c in PyEval_EvalFrameEx () from /usr/lib64/libpython2.7.so.1.0
    (gdb) bt
    #0  0x00007ffff7aef93c in PyEval_EvalFrameEx () from /usr/lib64/libpython2.7.so.1.0
    #1  0x00007ffff7af5303 in PyEval_EvalCodeEx () from /usr/lib64/libpython2.7.so.1.0
    #2  0x00007ffff7adc858 in ?? () from /usr/lib64/libpython2.7.so.1.0
    #3  0x00007ffff7ad840d in PyObject_Call () from /usr/lib64/libpython2.7.so.1.0
    #4  0x00007ffff7af1082 in PyEval_EvalFrameEx () from /usr/lib64/libpython2.7.so.1.0
    #5  0x00007ffff7af233d in PyEval_EvalFrameEx () from /usr/lib64/libpython2.7.so.1.0
    #6  0x00007ffff7af233d in PyEval_EvalFrameEx () from /usr/lib64/libpython2.7.so.1.0
    #7  0x00007ffff7af5303 in PyEval_EvalCodeEx () from /usr/lib64/libpython2.7.so.1.0
    #8  0x00007ffff7adc5b6 in ?? () from /usr/lib64/libpython2.7.so.1.0
    #9  0x00007ffff7ad840d in PyObject_Call () from /usr/lib64/libpython2.7.so.1.0
    #10 0x00007ffff7ad9171 in ?? () from /usr/lib64/libpython2.7.so.1.0
    #11 0x00007ffff7ad840d in PyObject_Call () from /usr/lib64/libpython2.7.so.1.0
    #12 0x00007ffff7aeeb62 in PyEval_CallObjectWithKeywords () from /usr/lib64/libpython2.7.so.1.0
    #13 0x00007ffff7acc757 in ?? () from /usr/lib64/libpython2.7.so.1.0
    #14 0x00007ffff7828e0f in start_thread () from /lib64/libpthread.so.0
    #15 0x00007ffff755c7dd in clone () from /lib64/libc.so.6

**Update 3**

I installed gdbinit from http://hg.python.org/cpython/file/default/Misc/gdbinit
and the debugging symbols from http://download.opensuse.org/debug/distribution/12.3/repo/oss/suse/x86_64/

    (gdb) pystack
    No symbol &quot;_PyUnicode_AsString&quot; in current context.

What now?

**Update 4**
We installed the a new RPM (python-2.7.5-3.1.x86_64). We get less segfaults, but they still happen.
Here is the link to repository:

http://download.opensuse.org/repositories/devel:/languages:/python:/Factory/openSUSE_12.3/x86_64/ 

**Update 5**
Solved my initial problem:

It was http://bugs.python.org/issue1856 (shutdown (exit) can hang or segfault with daemon threads running)

Related: https://stackoverflow.com/questions/18098475/detect-interpreter-shut-down-in-daemon-thread


How to debug a Python segmentation fault?

I&#39;m trying to compile and run following program without `main()` function in `C`. I have compiled my program using the following command.

    gcc -nostartfiles nomain.c
And compiler gives warning

    /usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400340

Ok, No problem. then, I have run executable file(a.out), both `printf` statements print successfully, and then get **segmentation fault**. 

So, my question is, **Why segmentation fault after successfully execute print statements?**

my code:

    #include &lt;stdio.h&gt;

    void nomain()
    {
            printf(&quot;Hello World...\n&quot;);
            printf(&quot;Successfully run without main...\n&quot;);
    }

**output:**

&lt;!-- language: lang-none --&gt;

    Hello World...
    Successfully run without main...
    Segmentation fault (core dumped)

**Note:** 

Here, `-nostartfiles` gcc flag prevents the compiler from using standard startup files when linking


Compile and run program without main() in C

What is the correct interpretation of the following segfault messages?

```none
segfault at 10 ip 00007f9bebcca90d sp 00007fffb62705f0 error 4 in libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]
segfault at 10 ip 00007fa44d78890d sp 00007fff43f6b720 error 4 in libQtWebKit.so.4.5.2[7fa44d2f8000+f6f000]
segfault at 11 ip 00007f2b0022acee sp 00007fff368ea610 error 4 in libQtWebKit.so.4.5.2[7f2aff9f7000+f6f000]
segfault at 11 ip 00007f24b21adcee sp 00007fff7379ded0 error 4 in libQtWebKit.so.4.5.2[7f24b197a000+f6f000]
```



Interpreting segfault messages

I think the question says it all. An example covering most standards from C89 to C11 would be helpful. I though of this one, but I guess it is just undefined behaviour:

    #include &lt;stdio.h&gt;
    
    int main( int argc, char* argv[] )
    {
      const char *s = NULL;
      printf( &quot;%c\n&quot;, s[0] );
      return 0;
    }

**EDIT:**

As some votes requested clarification: I wanted to have a program with an usual programming error (the simplest I could think of was an segfault), that is *guaranteed* (by standard) to abort. This is a bit different to the minimal segfault question, which don&#39;t care about this insurance.

What is the simplest standard conform way to produce a Segfault in C?

This can be a very simple question, I&#39;m am attempting to debug an application which generates the following segfault error in the `kern.log`

`kernel: myapp[15514]: segfault at 794ef0 ip 080513b sp 794ef0 error 6 in myapp[8048000+24000]`

Here are my questions: 

 1. Is there any documentation as to what are the diff error numbers on segfault, in this instance it is error 6, but i&#39;ve seen error 4, 5

 2. What is the meaning of the information `at bf794ef0 ip 0805130b sp bf794ef0 and myapp[8048000+24000]`?

So far i was able to compile with symbols, and when i do a `x 0x8048000+24000` it returns a symbol, is that the correct way of doing it? My assumptions thus far are the following:

- sp = stack pointer?
- ip = instruction pointer
- at = ????
- myapp[8048000+24000] = address of symbol?

How do you read a segfault kernel log message

I have a multithreaded C program, which consistently generates a segmentation fault at a specific point in the program. When I run it with gdb, no fault is shown. Can you think of any reason why the fault might occur only when not using the debugger? It&#39;s pretty annoying not being able to use it to find the problem!

segfault only when NOT using debugger

&gt; NOTE: We have a lot of segfault questions, with largely the same
&gt; answers, so I&#39;m trying to collapse them into a canonical question like
&gt; we have for [undefined reference][1].
&gt; 
&gt; Although we have a question covering [what a segmentation fault
&gt; is][2], it covers the **what**, but doesn&#39;t list many reasons. The top answer says &quot;there are many reasons&quot;, and only lists one, and most of the other answers don&#39;t list any reasons.
&gt;
&gt; All in all, I believe we need a **well-organized community wiki** on this topic, which lists all the common causes (and then some) to get segfaults. The purpose is to aid in debugging, as mentioned in the answer&#39;s disclaimer.

I know what a segmentation fault is, but it can be hard to spot in the code without knowing what they often look like. Although there are, no doubt, far too many to list exhaustively, **what are the most common causes of segmentation faults** in C and C++?


  [1]: https://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix
  [2]: https://stackoverflow.com/questions/2346806/what-is-segmentation-fault

Definitive List of Common Reasons for Segmentation Faults

I&#39;ve been banging my head against the wall for the better part of an hour trying to figure out what&#39;s going wrong here, and I&#39;m sure (or rather hoping) it&#39;s something fairly obvious that I&#39;m overlooking. I&#39;m using Ruby 1.9.1, Sinatra 1.0, and RMagick 2.13.1. ImageMagick and RMagick are correctly installed and functional—I&#39;ve successfully manipulated and saved images from irb.

The relevant part of the params array (formatting changes for the sake of readability):

    {&quot;admin_user_new_image_file&quot;=&gt;
        {
            :filename=&gt;&quot;freddie-on-shetland-pony.png&quot;,
            :type=&gt;&quot;image/png&quot;, 
            :name=&gt;&quot;admin_user_new_image_file&quot;, 
            :tempfile=&gt;#&lt;File:/var/folders/a7/a7pO5jMcGLCww9XBGRvWfE+++TI/-Tmp-/RackMultipart20100514-20700-o2tkqu-0&gt;,
            :head=&gt;&quot;Content-Disposition: form-data; name=\&quot;admin_user_new_image_file\&quot;; filename=\&quot;freddie-on-shetland-pony.png\&quot;\r\nContent-Type: image/png\r\n&quot;
        }
    }

The relevant code:

    post &quot;/admin/user/:account_name/image/new/&quot; do
      if params[:admin_user_new_image_file][:tempfile]
        thumbnail = Magick::Image.read(&quot;png:&quot;+params[:admin_user_new_image_file][:tempfile].path).first
      end
    end

The error (line 229 is the line starting with &quot;thumbnail = &quot;:

    config.ru:229: [BUG] Segmentation fault
    ruby 1.9.1p376 (2009-12-07 revision 26041) [i386-darwin10.3.0]
    
    -- control frame ----------
    c:0042 p:---- s:0196 b:0196 l:000195 d:000195 CFUNC  :read
    c:0041 p:0121 s:0192 b:0192 l:001ab8 d:000191 LAMBDA config.ru:229
    c:0040 p:---- s:0189 b:0189 l:000188 d:000188 FINISH
    c:0039 p:---- s:0187 b:0187 l:000186 d:000186 CFUNC  :call
    c:0038 p:0018 s:0184 b:0184 l:001d78 d:000183 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865
    c:0037 p:---- s:0182 b:0182 l:000181 d:000181 FINISH
    c:0036 p:---- s:0180 b:0180 l:000179 d:000179 CFUNC  :instance_eval
    c:0035 p:0016 s:0177 b:0175 l:000174 d:000174 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521
    c:0034 p:0024 s:0171 b:0171 l:000148 d:000170 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:500
    c:0033 p:---- s:0169 b:0169 l:000168 d:000168 FINISH
    c:0032 p:---- s:0167 b:0167 l:000166 d:000166 CFUNC  :catch
    c:0031 p:0140 s:0163 b:0163 l:000148 d:000162 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497
    c:0030 p:---- s:0154 b:0154 l:000153 d:000153 FINISH
    c:0029 p:---- s:0152 b:0152 l:000151 d:000151 CFUNC  :each
    c:0028 p:0073 s:0149 b:0149 l:000148 d:000148 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476
    c:0027 p:0076 s:0141 b:0141 l:000140 d:000140 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:601
    c:0026 p:0009 s:0137 b:0137 l:000138 d:000136 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411
    c:0025 p:---- s:0135 b:0135 l:000134 d:000134 FINISH
    c:0024 p:---- s:0133 b:0133 l:000132 d:000132 CFUNC  :instance_eval
    c:0023 p:0012 s:0130 b:0130 l:000121 d:000129 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566
    c:0022 p:---- s:0128 b:0128 l:000127 d:000127 FINISH
    c:0021 p:---- s:0126 b:0126 l:000125 d:000125 CFUNC  :catch
    c:0020 p:0013 s:0122 b:0122 l:000121 d:000121 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566
    c:0019 p:0098 s:0115 b:0115 l:000138 d:000138 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411
    c:0018 p:0019 s:0108 b:0108 l:000107 d:000107 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:399
    c:0017 p:0014 s:0104 b:0104 l:000103 d:000103 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24
    c:0016 p:0150 s:0098 b:0098 l:000097 d:000097 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/methodoverride.rb:24
    c:0015 p:0031 s:0092 b:0092 l:000091 d:000091 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18
    c:0014 p:0018 s:0084 b:0084 l:002080 d:000083 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979
    c:0013 p:0032 s:0082 b:0082 l:000081 d:000081 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:1005
    c:0012 p:0011 s:0078 b:0078 l:002080 d:002080 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979
    c:0011 p:0100 s:0074 b:0074 l:000ff0 d:000ff0 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:47
    c:0010 p:0022 s:0068 b:0068 l:000067 d:000067 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:35
    c:0009 p:0014 s:0064 b:0064 l:000063 d:000063 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24
    c:0008 p:0031 s:0058 b:0058 l:000057 d:000057 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18
    c:0007 p:0014 s:0050 b:0050 l:000049 d:000049 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/content_length.rb:13
    c:0006 p:0320 s:0042 b:0042 l:000041 d:000041 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/handler/webrick.rb:48
    c:0005 p:0256 s:0030 b:0030 l:000029 d:000029 METHOD /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:111
    c:0004 p:0382 s:0020 b:0020 l:000019 d:000019 METHOD /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:70
    c:0003 p:0123 s:0009 b:0009 l:000bc8 d:000008 BLOCK  /usr/local/lib/ruby/1.9.1/webrick/server.rb:183
    c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
    c:0001 p:---- s:0002 b:0002 l:000001 d:000001 TOP   
    ---------------------------
    -- Ruby level backtrace information-----------------------------------------
    config.ru:229:in `read&#39;
    config.ru:229:in `block (2 levels) in &lt;main&gt;&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865:in `block in route&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521:in `instance_eval&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521:in `route_eval&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:500:in `block (2 levels) in route!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497:in `catch&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497:in `block in route!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476:in `each&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476:in `route!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:601:in `dispatch!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411:in `block in call!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `instance_eval&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `block in invoke&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `catch&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `invoke&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411:in `call!&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:399:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/methodoverride.rb:24:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `block in call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:1005:in `synchronize&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:47:in `_call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:35:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/content_length.rb:13:in `call&#39;
    /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/handler/webrick.rb:48:in `service&#39;
    /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service&#39;
    /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run&#39;
    /usr/local/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread&#39;
    
    -- C level backtrace information -------------------------------------------
    0x10010cd8d 0   libruby.dylib                       0x000000010010cd8d rb_vm_bugreport + 77
    0x10002b184 1   libruby.dylib                       0x000000010002b184 report_bug + 260
    0x10002b318 2   libruby.dylib                       0x000000010002b318 rb_bug + 200
    0x1000b7124 3   libruby.dylib                       0x00000001000b7124 sigsegv + 132
    0x7fff8301c80a 4   libSystem.B.dylib                   0x00007fff8301c80a _sigtramp + 26
    0x1032313ac 5   libMagickCore.3.dylib               0x00000001032313ac Splay + 300
    0x103119245 6   libMagickCore.3.dylib               0x0000000103119245 AcquirePixelCache + 325
    0x1031cb317 7   libMagickCore.3.dylib               0x00000001031cb317 AcquireImage + 375
    0x10333035b 8   libMagickCore.3.dylib               0x000000010333035b ReadPNGImage + 155
    0x1031418fd 9   libMagickCore.3.dylib               0x00000001031418fd ReadImage + 2221
    0x101f1b72b 10  RMagick2.bundle                     0x0000000101f1b72b rd_image + 339
    0x101f1b59b 11  RMagick2.bundle                     0x0000000101f1b59b Image_read + 36
    0x1000fd0e4 12  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 13  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 14  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 15  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x100106643 16  libruby.dylib                       0x0000000100106643 rb_vm_invoke_proc + 691
    0x100106ccd 17  libruby.dylib                       0x0000000100106ccd vm_call0 + 1085
    0x1000317c6 18  libruby.dylib                       0x00000001000317c6 rb_method_call + 406
    0x1000fd0e4 19  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 20  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 21  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 22  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x100105ce6 23  libruby.dylib                       0x0000000100105ce6 yield_under + 710
    0x100106188 24  libruby.dylib                       0x0000000100106188 specific_eval + 72
    0x1000fd0e4 25  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 26  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 27  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 28  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x10010b6bf 29  libruby.dylib                       0x000000010010b6bf rb_f_catch + 639
    0x1000fd0e4 30  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 31  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 32  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 33  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x10010aac9 34  libruby.dylib                       0x000000010010aac9 rb_yield + 505
    0x100007902 35  libruby.dylib                       0x0000000100007902 rb_ary_each + 82
    0x1000fd0e4 36  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 37  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 38  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 39  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x100105ce6 40  libruby.dylib                       0x0000000100105ce6 yield_under + 710
    0x100106188 41  libruby.dylib                       0x0000000100106188 specific_eval + 72
    0x1000fd0e4 42  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 43  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 44  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 45  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x10010b6bf 46  libruby.dylib                       0x000000010010b6bf rb_f_catch + 639
    0x1000fd0e4 47  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
    0x1000fe9b0 48  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
    0x1000ff8fc 49  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
    0x100104b93 50  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
    0x100106643 51  libruby.dylib                       0x0000000100106643 rb_vm_invoke_proc + 691
    0x100111803 52  libruby.dylib                       0x0000000100111803 thread_start_func_2 + 835
    0x100111921 53  libruby.dylib                       0x0000000100111921 thread_start_func_1 + 17
    0x7fff82ff58b6 54  libSystem.B.dylib                   0x00007fff82ff58b6 _pthread_start + 331
    0x7fff82ff5769 55  libSystem.B.dylib                   0x00007fff82ff5769 thread_start + 13
    
    [NOTE]
    You may encounter a bug of Ruby interpreter. Bug reports are welcome.
    For details: http://www.ruby-lang.org/bugreport.html
    
    Abort trap

Anyone have any idea what&#39;s going on? Thanks!

Why is this RMagick call generating a segmentation fault?

I&#39;m having a problem with some program, I have searched about segmentation faults, by I don&#39;t understand them quite well, the only thing I know is that presumably I am trying to access some memory I shouldn&#39;t. The problem is that I see my code and don&#39;t understand what I am doing wrong. 

    #include&lt;stdio.h&gt;
    #include&lt;math.h&gt;
    #include&lt;stdlib.h&gt;

    #define   lambda   2.0
    #define   g        1.0
    #define   Lx       100
    #define   F0       1.0
    #define   Tf       10
    #define   h       0.1
    #define   e       0.00001

    FILE   *file;

    double F[1000][1000000];

    void Inicio(double D[1000][1000000]) {
    int i;
    for (i=399; i&lt;600; i++) {
        D[i][0]=F0;
    }
    }

    void Iteration (double A[1000][1000000]) {
    long int i,k;
    for (i=1; i&lt;1000000; i++) {
        A[0][i]= A[0][i-1] + e/(h*h*h*h)*g*g*(A[2][i-1] - 4.0*A[1][i-1] + 6.0*A[0][i-1]-4.0*A[998][i-1] + A[997][i-1]) + 2.0*g*e/(h*h)*(A[1][i-1] - 2*A[0][i-1] + A[998][i-1]) + e*A[0][i-1]*(lambda-A[0][i-1]*A[0][i-1]);
        A[1][i]= A[1][i-1] + e/(h*h*h*h)*g*g*(A[3][i-1] - 4.0*A[2][i-1] + 6.0*A[1][i-1]-4.0*A[0][i-1] + A[998][i-1]) + 2.0*g*e/(h*h)*(A[2][i-1] - 2*A[1][i-1] + A[0][i-1]) + e*A[1][i-1]*(lambda-A[1][i-1]*A[1][i-1]);
        for (k=2; k&lt;997; k++) {
            A[k][i]= A[k][i-1] + e/(h*h*h*h)*g*g*(A[k+2][i-1] - 4.0*A[k+1][i-1] + 6.0*A[k][i-1]-4.0*A[k-1][i-1] + A[k-2][i-1]) + 2.0*g*e/(h*h)*(A[k+1][i-1] - 2*A[k][i-1] + A[k-1][i-1]) + e*A[k][i-1]*(lambda-A[k][i-1]*A[k][i-1]);
        }
        A[997][i] = A[997][i-1] + e/(h*h*h*h)*g*g*(A[0][i-1] - 4*A[998][i-1] + 6*A[997][i-1] - 4*A[996][i-1] + A[995][i-1]) + 2.0*g*e/(h*h)*(A[998][i-1] - 2*A[997][i-1] + A[996][i-1]) + e*A[997][i-1]*(lambda-A[997][i-1]*A[997][i-1]);
        A[998][i] = A[998][i-1] + e/(h*h*h*h)*g*g*(A[1][i-1] - 4*A[0][i-1] + 6*A[998][i-1] - 4*A[997][i-1] + A[996][i-1]) + 2.0*g*e/(h*h)*(A[0][i-1] - 2*A[998][i-1] + A[997][i-1]) + e*A[998][i-1]*(lambda-A[998][i-1]*A[998][i-1]);
        A[999][i]=A[0][i];
    }
    }

    main() {
    long int i,j;
    Inicio(F);
    Iteration(F);
    file = fopen(&quot;P1.txt&quot;,&quot;wt&quot;);
    for (i=0; i&lt;1000000; i++) {
        for (j=0; j&lt;1000; j++) {
            fprintf(file,&quot;%lf \t %.4f \t %lf\n&quot;, 1.0*j/10.0, 1.0*i, F[j][i]);
        }
    }
    fclose(file);
    }

Thanks for your time. 

segmentation fault : 11

This question is meant to be used as reference for all frequently asked questions of the nature:

Why do I get a mysterious crash or &quot;segmentation fault&quot; when I copy/scan data to the address where an uninitialised pointer points to?

For example:

    char* ptr;
    strcpy(ptr, &quot;hello world&quot;); // crash here!

or

    char* ptr;
    scanf(&quot;%s&quot;, ptr); // crash here!


Crash or &quot;segmentation fault&quot; when data is copied/scanned/read to an uninitialized pointer

I&#39;m trying to execute a [Python script](https://pastebin.com/jSjn1aaD), but I am getting the following error:

    Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

I&#39;m using python 3.5.2 on a Linux Mint 18.1 Serena OS

Can someone tell me why this happens, and how can I solve?


Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

My gdb backtrace gives:

    (gdb) backtrace
    #0  0x00000000 in ?? ()
    #1  0x0804a211 in init () at example1.cpp:147
    #2  0x0804a6bc in main (argc=1, argv=0xbffff3d4) at example1.cpp:283

Not very informative. Eclipse debugger at least lets me see that it stops on line 3 below:

    // Create a vertex array object
    GLuint vao;
    glGenVertexArrays( 1, &amp;vao );
    glBindVertexArray( vao );

This is a very common block to see in gl programming, and I&#39;m even running other code with the same block with no problem. So I&#39;m baffled.

Build output from running make:

    g++ -g -DFREEGLUT_STATIC -DGLEW_STATIC -I../../include example1.cpp ../../Commo/InitShader.o  -L/usr/lib/mesa -lGLEW -lglut -lGL -lX11  -lm  -o example1

Program containing the problem:
    
    // rotating cube with two texture objects
    // change textures with 1 and 2 keys

    #include &quot;Angel.h&quot;

    const int  NumTriangles = 12; // (6 faces)(2 triangles/face)
    const int  NumVertices  = 3 * NumTriangles;
    const int  TextureSize  = 64;

    typedef Angel::vec4 point4;
    typedef Angel::vec4 color4;

    // Texture objects and storage for texture image
    GLuint textures[2];

    GLubyte image[TextureSize][TextureSize][3];
    GLubyte image2[TextureSize][TextureSize][3];

    // Vertex data arrays
    point4  points[NumVertices];
    color4  quad_colors[NumVertices];
    vec2    tex_coords[NumVertices];

    // Array of rotation angles (in degrees) for each coordinate axis
    enum { Xaxis = 0, Yaxis = 1, Zaxis = 2, NumAxes = 3 };
    int      Axis = Xaxis;
    GLfloat  Theta[NumAxes] = { 0.0, 0.0, 0.0 };
    GLuint   theta;

    //----------------------------------------------------------------------------
    int Index = 0;
    void quad( int a, int b, int c, int d )
    {
        point4 vertices[8] = {
            point4( -0.5, -0.5,  0.5, 1.0 ),
            point4( -0.5,  0.5,  0.5, 1.0 ),
            point4(  0.5,  0.5,  0.5, 1.0 ),
            point4(  0.5, -0.5,  0.5, 1.0 ),
            point4( -0.5, -0.5, -0.5, 1.0 ),
            point4( -0.5,  0.5, -0.5, 1.0 ),
            point4(  0.5,  0.5, -0.5, 1.0 ),
            point4(  0.5, -0.5, -0.5, 1.0 )
        };

        color4 colors[8] = {
            color4( 0.0, 0.0, 0.0, 1.0 ),  // black
            color4( 1.0, 0.0, 0.0, 1.0 ),  // red
            color4( 1.0, 1.0, 0.0, 1.0 ),  // yellow
            color4( 0.0, 1.0, 0.0, 1.0 ),  // green
            color4( 0.0, 0.0, 1.0, 1.0 ),  // blue
            color4( 1.0, 0.0, 1.0, 1.0 ),  // magenta
            color4( 0.0, 1.0, 1.0, 1.0 ),  // white
            color4( 1.0, 1.0, 1.0, 1.0 )   // cyan
        };

        quad_colors[Index] = colors[a];
        points[Index] = vertices[a];
        tex_coords[Index] = vec2( 0.0, 0.0 );
        Index++;

        quad_colors[Index] = colors[a];
        points[Index] = vertices[b];
        tex_coords[Index] = vec2( 0.0, 1.0 );
        Index++;

        quad_colors[Index] = colors[a];
        points[Index] = vertices[c];
        tex_coords[Index] = vec2( 1.0, 1.0 );
        Index++;

        quad_colors[Index] = colors[a];
        points[Index] = vertices[a];
        tex_coords[Index] = vec2( 0.0, 0.0 );
        Index++;

        quad_colors[Index] = colors[a];
        points[Index] = vertices[c];
        tex_coords[Index] = vec2( 1.0, 1.0 );
        Index++;

        quad_colors[Index] = colors[a];
        points[Index] = vertices[d];
        tex_coords[Index] = vec2( 1.0, 0.0 );
        Index++;
    }

    //----------------------------------------------------------------------------
    void colorcube()
    {
        quad( 1, 0, 3, 2 );
        quad( 2, 3, 7, 6 );
        quad( 3, 0, 4, 7 );
        quad( 6, 5, 1, 2 );
        quad( 4, 5, 6, 7 );
        quad( 5, 4, 0, 1 );
    }

    //----------------------------------------------------------------------------
    void init()
    {
        colorcube();

        // Create a checkerboard pattern
        for ( int i = 0; i &lt; 64; i++ ) {
            for ( int j = 0; j &lt; 64; j++ ) {
                GLubyte c = (((i &amp; 0x8) == 0) ^ ((j &amp; 0x8)  == 0)) * 255;
                image[i][j][0]  = c;
                image[i][j][1]  = c;
                image[i][j][2]  = c;
                image2[i][j][0] = c;
                image2[i][j][1] = 0;
                image2[i][j][2] = c;
            }
        }

        // Initialize texture objects
        glGenTextures( 2, textures );

        glBindTexture( GL_TEXTURE_2D, textures[0] );
        glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, TextureSize, TextureSize, 0,
            GL_RGB, GL_UNSIGNED_BYTE, image );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );

        glBindTexture( GL_TEXTURE_2D, textures[1] );
        glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, TextureSize, TextureSize, 0,
            GL_RGB, GL_UNSIGNED_BYTE, image2 );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
        glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );

        glActiveTexture( GL_TEXTURE0 );
        glBindTexture( GL_TEXTURE_2D, textures[0] );

        // Create a vertex array object
        GLuint vao;
        glGenVertexArrays( 1, &amp;vao );
        glBindVertexArray( vao );

        // Create and initialize a buffer object
        GLuint buffer;
        glGenBuffers( 1, &amp;buffer );
        glBindBuffer( GL_ARRAY_BUFFER, buffer );
        glBufferData( GL_ARRAY_BUFFER,
            sizeof(points) + sizeof(quad_colors) + sizeof(tex_coords),
            NULL, GL_STATIC_DRAW );

        // Specify an offset to keep track of where we&#39;re placing data in our
        //   vertex array buffer.  We&#39;ll use the same technique when we
        //   associate the offsets with vertex attribute pointers.
        GLintptr offset = 0;
        glBufferSubData( GL_ARRAY_BUFFER, offset, sizeof(points), points );
        offset += sizeof(points);

        glBufferSubData( GL_ARRAY_BUFFER, offset,
            sizeof(quad_colors), quad_colors );
        offset += sizeof(quad_colors);

        glBufferSubData( GL_ARRAY_BUFFER, offset, sizeof(tex_coords), tex_coords );

        // Load shaders and use the resulting shader program
        GLuint program = InitShader( &quot;vshader71.glsl&quot;, &quot;fshader71.glsl&quot; );
        glUseProgram( program );

        // set up vertex arrays
        offset = 0;
        GLuint vPosition = glGetAttribLocation( program, &quot;vPosition&quot; );
        glEnableVertexAttribArray( vPosition );
        glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0,
            BUFFER_OFFSET(offset) );
        offset += sizeof(points);

        GLuint vColor = glGetAttribLocation( program, &quot;vColor&quot; ); 
        glEnableVertexAttribArray( vColor );
        glVertexAttribPointer( vColor, 4, GL_FLOAT, GL_FALSE, 0,
            BUFFER_OFFSET(offset) );
        offset += sizeof(quad_colors);

        GLuint vTexCoord = glGetAttribLocation( program, &quot;vTexCoord&quot; );
        glEnableVertexAttribArray( vTexCoord );
        glVertexAttribPointer( vTexCoord, 2, GL_FLOAT, GL_FALSE, 0,
            BUFFER_OFFSET(offset) );

        // Set the value of the fragment shader texture sampler variable
        //   (&quot;texture&quot;) to the the appropriate texture unit. In this case,
        //   zero, for GL_TEXTURE0 which was previously set by calling
        //   glActiveTexture().
        glUniform1i( glGetUniformLocation(program, &quot;texture&quot;), 0 );

        theta = glGetUniformLocation( program, &quot;theta&quot; );

        glEnable( GL_DEPTH_TEST );

        glClearColor( 1.0, 1.0, 1.0, 1.0 );
    }

    void display( void )
    {
        glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

        glUniform3fv( theta, 1, Theta );

        glDrawArrays( GL_TRIANGLES, 0, NumVertices );

        glutSwapBuffers();
    }

    //----------------------------------------------------------------------------
    void mouse( int button, int state, int x, int y )
    {
        if ( state == GLUT_DOWN ) {
            switch( button ) {
            case GLUT_LEFT_BUTTON:    Axis = Xaxis;  break;
            case GLUT_MIDDLE_BUTTON:  Axis = Yaxis;  break;
            case GLUT_RIGHT_BUTTON:   Axis = Zaxis;  break;
            }
        }
    }

    //----------------------------------------------------------------------------
    void idle( void )
    {
        Theta[Axis] += 0.01;

        if ( Theta[Axis] &gt; 360.0 ) {
            Theta[Axis] -= 360.0;
        }

        glutPostRedisplay();
    }

    //----------------------------------------------------------------------------
    void keyboard( unsigned char key, int mousex, int mousey )
    {
        switch( key ) {
        case 033: // Escape Key
        case &#39;q&#39;: case &#39;Q&#39;:
            exit( EXIT_SUCCESS );
            break;
        case &#39;1&#39;:
            glBindTexture( GL_TEXTURE_2D, textures[0] );
            break;

        case &#39;2&#39;:
            glBindTexture( GL_TEXTURE_2D, textures[1] );
            break;
        }

        glutPostRedisplay();
    }

    //----------------------------------------------------------------------------
    int main( int argc, char **argv )
    {
        glutInit( &amp;argc, argv );
        glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH );
        glutInitWindowSize( 512, 512 );
        glutInitContextVersion( 3, 2 );
        glutInitContextProfile( GLUT_CORE_PROFILE );
        glutCreateWindow( &quot;Color Cube&quot; );

        glewInit();

        init();

        glutDisplayFunc( display );
        glutKeyboardFunc( keyboard );
        glutMouseFunc( mouse );
        glutIdleFunc( idle );

        glutMainLoop();
        return 0;
    }

Segmentation fault at glGenVertexArrays( 1, &amp;vao );

Is there any gcc option I can set that will give me the line number of the segmentation fault?

I know I can:

 1. Debug line by line
 2. Put printfs in the code to narrow down.

Edits:

 1. `bt` / `where` on gdb give No stack.
 2. [Helpful suggestion][1]


  [1]: https://stackoverflow.com/a/77336/24874

Line number of segmentation fault

&gt; **Updates**
&gt; 
&gt; [X] I discovered this happen when `TLS::credentials creds` is declared on
&gt; global scope but if I declare it outside seg fault won&#39;t happen. 
&gt; 
&gt; I need it to be global because it helps with caching certificates and
&gt; that multiple threads can use certificates created by other threads without
&gt; spending time on creating new certificates.
&gt;
&gt; [X] I further reduced code from 200 lines approx. to 100 lines

I&#39;m using Botan to create a TLS application and my application crash with a seg fault at end of the application. 

I made an attempt to debug this with Valgrind but it leading nowhere.

Here is the stack trace from Valgrind,

    ==3841967== Invalid write of size 8
    ==3841967==    at 0x4842964: memset (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==3841967==    by 0x566A82F: Botan::deallocate_memory(void*, unsigned long, unsigned long) (in /usr/lib/x86_64-linux-gnu/libbotan-2.so.12.12.1)
    ==3841967==    by 0x55E1A4D: ??? (in /usr/lib/x86_64-linux-gnu/libbotan-2.so.12.12.1)
    ==3841967==    by 0x40EC7B: std::_Sp_counted_base&lt;(__gnu_cxx::_Lock_policy)2&gt;::_M_release() (shared_ptr_base.h:155)
    ==3841967==    by 0x40EC29: std::__shared_count&lt;(__gnu_cxx::_Lock_policy)2&gt;::~__shared_count() (shared_ptr_base.h:730)
    ==3841967==    by 0x41112D: std::__shared_ptr&lt;Botan::RSA_Public_Data const, (__gnu_cxx::_Lock_policy)2&gt;::~__shared_ptr() (shared_ptr_base.h:1169)
    ==3841967==    by 0x411107: std::shared_ptr&lt;Botan::RSA_Public_Data const&gt;::~shared_ptr() (shared_ptr.h:103)
    ==3841967==    by 0x41109D: Botan::RSA_PublicKey::~RSA_PublicKey() (rsa.h:25)
    ==3841967==    by 0x410FC1: Botan::RSA_PrivateKey::~RSA_PrivateKey() (rsa.h:92)
    ==3841967==    by 0x410DC5: Botan::RSA_PrivateKey::~RSA_PrivateKey() (rsa.h:92)
    ==3841967==    by 0x410E8A: std::_Sp_counted_ptr&lt;Botan::RSA_PrivateKey*, (__gnu_cxx::_Lock_policy)2&gt;::_M_dispose() (shared_ptr_base.h:377)
    ==3841967==    by 0x40EC7B: std::_Sp_counted_base&lt;(__gnu_cxx::_Lock_policy)2&gt;::_M_release() (shared_ptr_base.h:155)
    ==3841967==  Address 0x9419080 is not stack&#39;d, malloc&#39;d or (recently) free&#39;d
    ==3841967== 
    ==3841967== 
    ==3841967== Process terminating with default action of signal 11 (SIGSEGV)
    ==3841967==  Access not within mapped region at address 0x9419080
    ==3841967==    at 0x4842964: memset (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==3841967==    by 0x566A82F: Botan::deallocate_memory(void*, unsigned long, unsigned long) (in /usr/lib/x86_64-linux-gnu/libbotan-2.so.12.12.1)
    ==3841967==    by 0x55E1A4D: ??? (in /usr/lib/x86_64-linux-gnu/libbotan-2.so.12.12.1)
    ==3841967==    by 0x40EC7B: std::_Sp_counted_base&lt;(__gnu_cxx::_Lock_policy)2&gt;::_M_release() (shared_ptr_base.h:155)
    ==3841967==    by 0x40EC29: std::__shared_count&lt;(__gnu_cxx::_Lock_policy)2&gt;::~__shared_count() (shared_ptr_base.h:730)
    ==3841967==    by 0x41112D: std::__shared_ptr&lt;Botan::RSA_Public_Data const, (__gnu_cxx::_Lock_policy)2&gt;::~__shared_ptr() (shared_ptr_base.h:1169)
    ==3841967==    by 0x411107: std::shared_ptr&lt;Botan::RSA_Public_Data const&gt;::~shared_ptr() (shared_ptr.h:103)
    ==3841967==    by 0x41109D: Botan::RSA_PublicKey::~RSA_PublicKey() (rsa.h:25)
    ==3841967==    by 0x410FC1: Botan::RSA_PrivateKey::~RSA_PrivateKey() (rsa.h:92)
    ==3841967==    by 0x410DC5: Botan::RSA_PrivateKey::~RSA_PrivateKey() (rsa.h:92)
    ==3841967==    by 0x410E8A: std::_Sp_counted_ptr&lt;Botan::RSA_PrivateKey*, (__gnu_cxx::_Lock_policy)2&gt;::_M_dispose() (shared_ptr_base.h:377)
    ==3841967==    by 0x40EC7B: std::_Sp_counted_base&lt;(__gnu_cxx::_Lock_policy)2&gt;::_M_release() (shared_ptr_base.h:155)
    ==3841967==  If you believe this happened as a result of a stack
    ==3841967==  overflow in your program&#39;s main thread (unlikely but
    ==3841967==  possible), you can try to increase the size of the
    ==3841967==  main thread stack using the --main-stacksize= flag.
    ==3841967==  The main thread stack size used in this run was 8388608.
    ==3841967== 
    ==3841967== HEAP SUMMARY:
    ==3841967==     in use at exit: 149,626 bytes in 1,143 blocks
    ==3841967==   total heap usage: 211,782 allocs, 210,639 frees, 90,582,963 bytes allocated
    ==3841967== 
    ==3841967== LEAK SUMMARY:
    ==3841967==    definitely lost: 0 bytes in 0 blocks
    ==3841967==    indirectly lost: 0 bytes in 0 blocks
    ==3841967==      possibly lost: 1,352 bytes in 18 blocks
    ==3841967==    still reachable: 148,274 bytes in 1,125 blocks
    ==3841967==                       of which reachable via heuristic:
    ==3841967==                         newarray           : 1,536 bytes in 16 blocks
    ==3841967==         suppressed: 0 bytes in 0 blocks
    ==3841967== Rerun with --leak-check=full to see details of leaked memory
    ==3841967== 
    ==3841967== For lists of detected and suppressed errors, rerun with: -s
    ==3841967== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
    Segmentation fault (core dumped)

You can clone the Botan into your machine by issuing, 

    git clone https://github.com/randombit/botan.git

Then follow instructions from their [official website][1] to build &amp; install it.

You will need to create a Root Certificate Authority to use with the application and for that you must install OpenSSL on your machine.

Create a folder called `testApplication` and `cd` into it.

Then using Bash, issue the following series of commands to create a Root CA,

```sh
# Generate private key
openssl genrsa -des3 -out myCA.key 2048
# Generate root certificate
openssl req -x509 -new -nodes -key myCA.key -sha256 -days 825 -out myCA.pem
# Convert to Botan Format
openssl pkcs8 -topk8 -in myCA.key &gt; myCAKey.pkcs8.pem
```

Please use `thisispassword` as password.

Install clang compiler on your machine and then you can compile the source file as follows,

    clang++ example.cpp -o example  -Wthread-safety -Wall -Wextra -g -std=c++17 -pthread -lssl -lcrypto -lbotan-2 --I/usr/include/botan-2


example.cpp

    #include &lt;iostream&gt;
    #include &lt;string&gt;
    #include &lt;vector&gt;
    #include &lt;fstream&gt;
    #include &lt;sstream&gt;
    #include &lt;botan/tls_server.h&gt;
    #include &lt;botan/tls_callbacks.h&gt;
    #include &lt;botan/tls_session_manager.h&gt;
    #include &lt;botan/tls_policy.h&gt;
    #include &lt;botan/auto_rng.h&gt;
    #include &lt;botan/certstor.h&gt;
    #include &lt;botan/pk_keys.h&gt;
    #include &lt;botan/pkcs10.h&gt;
    #include &lt;botan/pkcs8.h&gt;
    #include &lt;botan/x509self.h&gt;
    #include &lt;botan/x509path.h&gt;
    #include &lt;botan/x509_ca.h&gt;
    #include &lt;botan/x509_ext.h&gt;
    #include &lt;botan/pk_algs.h&gt;
    #include &lt;botan/ber_dec.h&gt;
    #include &lt;botan/der_enc.h&gt;
    #include &lt;botan/oids.h&gt;
    #include &lt;botan/rsa.h&gt;
    
    namespace TLS
    {
        typedef std::chrono::duration&lt;int, std::ratio&lt;31556926&gt;&gt; years;
    
        class credentials : public Botan::Credentials_Manager
        {
        private:
            struct certificate
            {
                std::vector&lt;Botan::X509_Certificate&gt; certs;
                std::shared_ptr&lt;Botan::Private_Key&gt; key;
            };
    
            std::vector&lt;certificate&gt; creds;
            std::vector&lt;std::shared_ptr&lt;Botan::Certificate_Store&gt;&gt; store;
    
        public:
            void createCert(std::string hostname)
            {
                /**
                 * Initialize Root CA
                **/
    
                Botan::AutoSeeded_RNG rng;
    
                const Botan::X509_Certificate rootCert(&quot;myCA.pem&quot;);
    
                std::ifstream rootCertPrivateKeyFile(&quot;myCAKey.pkcs8.pem&quot;);
    
                Botan::DataSource_Stream rootCertPrivateKeyStream(rootCertPrivateKeyFile);
    
                std::unique_ptr&lt;Botan::Private_Key&gt; rootCertPrivateKey = Botan::PKCS8::load_key(rootCertPrivateKeyStream, &quot;thisispassword&quot;);
    
                Botan::X509_CA rootCA(rootCert, *rootCertPrivateKey, &quot;SHA-256&quot;, rng);
    
                /**
                * Generate a Cert &amp; Sign with Root CA
                **/
    
                Botan::X509_Cert_Options opts;
                std::shared_ptr&lt;Botan::Private_Key&gt; serverPrivateKeyShared(new Botan::RSA_PrivateKey(rng, 4096));
                Botan::RSA_PrivateKey* serverPrivateKey = (Botan::RSA_PrivateKey*)serverPrivateKeyShared.get();
    
                opts.common_name = hostname;
                opts.country = &quot;US&quot;;
    
                auto now = std::chrono::system_clock::now();
    
                Botan::X509_Time todayDate(now);
                Botan::X509_Time expireDate(now + years(1));
    
                Botan::PKCS10_Request req = Botan::X509::create_cert_req(opts, *serverPrivateKey, &quot;SHA-256&quot;, rng);
    
                auto serverCert = rootCA.sign_request(req, rng, todayDate, expireDate);
    
                /**
                 * Load Cert to In-Memory Database
                **/
    
                certificate cert;
    
                cert.certs.push_back(serverCert);
                cert.key = serverPrivateKeyShared;
    
                creds.push_back(cert);
            }
        };
    }; // namespace TLS
    
    TLS::credentials globalCreds;
    
    int main() {
        globalCreds.createCert(&quot;www.google.com&quot;);
    
        std::cout &lt;&lt; &quot;End&quot; &lt;&lt; &quot;\n&quot;;
    
        return 0;
    }

Here is the function from the Botan Lib that Valgrind refers to,

    void deallocate_memory(void* p, size_t elems, size_t elem_size)
       {
       if(p == nullptr)
          return;
    
       secure_scrub_memory(p, elems * elem_size);
    
    #if defined(BOTAN_HAS_LOCKING_ALLOCATOR)
       if(mlock_allocator::instance().deallocate(p, elems, elem_size))
          return;
    #endif
    
       std::free(p);
       }
    

  [1]: https://botan.randombit.net/handbook/building.html

All Segmentation Fault Solutions on Gang of Coders

Total of 29 Segmentation Fault Solutions