Hit `Control + L`. Works for me in Linux and Mac OS X as well with recent versions of GDB.


Depending on the environment you can try this key combination: &lt;kbd&gt;Ctrl&lt;/kbd&gt;+&lt;kbd&gt;L&lt;/kbd&gt;. That is: hold down the *Control* key, and type the *L* key.

But this may not work in all environments. You can also try the following: in gdb you can execute shell commands using `shell`: use this to call out to the shell to clear the terminal:

    shell clear



    @{
        int i = 0;
    }
    
    @helper Text() {
        &lt;input type=&quot;text&quot; name=&quot;Ans[@i].Text&quot; /&gt;
    }

`i` is not accessible in helper. How to access it?

Access global page variable in helper

I have a test project on TypeScript, code can found [here][1].

When I&#39;m creating new project with VS2012, an `app.ts` file is created. When I&#39;m changing it&#39;s content as shown by the link and adding new module called `GameModule`, I&#39;m getting compile error. When I&#39;m deleting `app.ts` and creating `Main.ts` instead, everything compiling fine, but there is a problem - only `Main.ts` is compiled to `Main.js`, and `GameModule.ts` stays uncompiled.

How can I make compiler to merge all the code in one JS?


  [1]: https://stackoverflow.com/questions/12913238/cannot-load-class-from-file-in-typescript

TypeScript compiling as a single JS file

Is it possible to clear the command window of gdb? I mean, is there a command in gdb that do the same (for the command windows) as the `clear` command in a bash terminal?

How clear gdb command screen?

<p>Is it possible to clear the command window of gdb? I mean, is there a command in gdb that do the same (for the command windows) as the <code>clear</code> command in a bash terminal?</p>


Is it possible to make `std::vector` of custom structs allocate aligned memory for further processing with SIMD instructions? If it is possible to do with `Allocator`, does anyone happen to have such an allocator he could share?

Making std::vector allocate aligned memory

How do I install `g++` for Fedora Linux? I have been searching the `dnf` command to install `g++` but didn&#39;t find anything.

How do I install it?

I have already installed `gcc`

How do I install g++ for Fedora?

What is copy elision? What is (named) return value optimization? What do they imply?

In what situations can they occur? What are limitations?

- If you were referenced to this question, you&#39;re probably looking for [**the introduction**][1].
- For a technical overview, see [**the standard reference**][2].
- See [**common cases** here][3].


  [1]: https://stackoverflow.com/a/12953129/673730
  [2]: https://stackoverflow.com/a/12953145/673730
  [3]: https://stackoverflow.com/a/12953150/673730

What are copy elision and return value optimization?

I use Visual Studio 2010 C++ and my project builds without errors but when I run it I get this. I am on Windows XP.



    &#39;Shaders.exe&#39;: Loaded &#39;C:\Documents and Settings\User\My Documents\Visual Studio        2010\Projects\Shaders\Win32\Debug\Shaders.exe&#39;, Symbols loaded.
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\ntdll.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\kernel32.dll&#39;, Cannot find or open the PDB  file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\qt-everywhere-opensource-src-4.8.3\bin\QtCored4.dll&#39;, Symbols  loaded.
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\user32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\gdi32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\ole32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\advapi32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\rpcrt4.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\secur32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\msvcrt.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\ws2_32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\ws2help.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\msvcp100d.dll&#39;, Symbols loaded.
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\msvcr100d.dll&#39;, Symbols loaded.
    &#39;Shaders.exe&#39;: Loaded &#39;C:\qt-everywhere-opensource-src-4.8.3\bin\QtGuid4.dll&#39;, Symbols loaded.
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\comdlg32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\comctl32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\shell32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\shlwapi.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\oleaut32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\imm32.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\winmm.dll&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\WINDOWS\system32\winspool.drv&#39;, Cannot find or open the PDB file
    &#39;Shaders.exe&#39;: Loaded &#39;C:\qt-everywhere-opensource-src-4.8.3\bin\QtOpenGLd4.dll&#39;, Symbols loaded.
   


Thanks

Cannot find or open the PDB file in Visual Studio C++ 2010

I am making a small vocabulary remembering program where words would would be flashed at me randomly for meanings. I want to use standard C++ library as Bjarne Stroustroup tells us, but I have encountered a seemingly strange problem right out of the gate. 

I want to change a `long` integer into `std::string` so as to be able to store it in a file. I have employed `to_string()` for the same. The problem is, when I compile it with g++ (version 4.7.0 as mentioned in its --‍version flag), it says:

    PS C:\Users\Anurag\SkyDrive\College\Programs&gt; g++ -std=c++0x ttd.cpp
    ttd.cpp: In function &#39;int main()&#39;:
    ttd.cpp:11:2: error: &#39;to_string&#39; is not a member of &#39;std&#39;

My program that gives this error is:

    #include &lt;string&gt;

    int main()
    {
        std::to_string(0);
        return 0;
    }

But, I know it can&#39;t be because msdn library [clearly says][1] it exists and [an earlier question][2] on Stack Overflow (for g++ version 4.5) says that it can be turned on with the `-std=c++0x` flag. What am I doing wrong?


  [1]: http://msdn.microsoft.com/en-us/library/ee404875.aspx
  [2]: https://stackoverflow.com/questions/7521617/c11-to-string-function-where

to_string is not a member of std, says g++ (mingw)

Per 7.5,

&gt; [errno] expands to a modifiable lvalue175) that has type int, the value of which is set to a positive error number by several library functions. It is unspecified whether errno is a macro or an identifier declared with external linkage. If a macro definition is suppressed in order to access an actual object, or a program defines an identifier with the name errno, the behavior is undefined.

&gt; 175) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue resulting from a function call (for example, *errno()).

It&#39;s not clear to me whether this is sufficient to require that `&amp;errno` not be a constraint violation. The C language has lvalues (such as register-storage-class variables; however these can only be automatic so `errno` could not be defined as such) for which the `&amp;` operator is a constraint violation.

If `&amp;errno` is legal C, is it required to be constant?


Is &amp;errno legal C?

I noticed that LSH seems a good way to find similar items with high-dimension properties.

After reading the paper http://www.slaney.org/malcolm/yahoo/Slaney2008-LSHTutorial.pdf, I&#39;m still confused with those formulas.

Does anyone know a blog or article that explains that the easy way?

How to understand Locality Sensitive Hashing?

When I use `malloc` in a C program, I get a warning:

    warning: incompatible implicit declaration of built-in function &#39;malloc&#39; [enabled by default]

I can then include `&lt;malloc.h&gt;` or `&lt;stdlib.h&gt;` to get rid of the `warning` although it works without it as well.

**So I was wondering, what&#39;s the difference between these headers and which one does `gcc` links when I don&#39;t include anything?**

(I&#39;m using `ubuntu 12.04 64-bit ` with `gcc 4.6.3`)

difference between &lt;stdlib.h&gt; and &lt;malloc.h&gt;

When I learned C, teacher told me all day long: &quot;Don&#39;t use goto, that&#39;s a bad habit, it&#39;s ugly, it&#39;s dangerous!&quot; and so on.

Why then, do some kernel programmers use `goto`, for example [in this function][1], where it could be replaced with a simple 

    while(condition) {} 

or 

    do {} while(condition);

I can&#39;t understand that. Is it better in some cases to use goto instead of `while`/`do`-`while`? And if so, why?


  [1]: https://github.com/torvalds/linux/blob/391e43da797a96aeb65410281891f6d0b0e9611c/kernel/sched/clock.c#L141

Why do some kernel programmers use goto instead of simple while loops?

In the course of my reading I came accross [WG14 Defect Report #51](http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_051.html) written in 1993 (or perhaps 1893, they left off the century and millennium). In the code sample there, apparently an operator spelled `-&gt;&gt;` is used on a pointer to a `struct`. I can&#39;t find it in any operator precedence tables I&#39;ve found, so I am wondering, is or was it ever an operator, and if so, what does (or did, as the case may be) this operator do?

At first I thought it was a typo, but it is reproduced twice more in the text and another time in the code sample in the response to the question, and I have a hard time believing it just slipped past at least two C experts without being noticed, when it jumped out at a novice like me. It&#39;s also at the focal point of the code, very easy to notice, and was never corrected.

Here is the code with added indentation:

    #include &lt;stdlib.h&gt;
    
    struct A {
        char x[1];
    };
    
    main()
    {
        struct A *p = (struct A *) malloc(sizeof(struct A) + 100);
        p-&gt;&gt;x[5] = &#39;?&#39;;  /* This is the key line [for both them and us] */
        return 0;
    }

I tried to compile this code with both a C and C++ compiler and it failed to parse in either one. Perhaps this was some operator in an early version of C that isn&#39;t used any more?

This feels suspiciously like the [What is the name of this operator: &quot;--&gt;&quot;?](https://stackoverflow.com/questions/1642028/what-is-the-name-of-this-operator) question, but I don&#39;t think this is a combination of two other operators, I don&#39;t see how it can be divided up and be valid.

Is this -&gt;&gt; an old operator or a typo/error?

When I write C programs in Linux, and then compile them using gcc, I am always curious about where those header files are. For example, where `stdio.h` is. More generally, where is `stdbool.h`?

What I want to know is not only where it is, but also how to get those places, for example, using shell command or using the C programming language.

How can I find the header files of the C programming language in Linux?

From the [GCC 4.8 draft changelog](http://gcc.gnu.org/gcc-4.8/changes.html#cxx):

&gt; G++ now implements the [C++11](http://gcc.gnu.org/gcc-4.8/cxx0x_status.html) `thread_local` keyword; this differs from
&gt; the GNU `__thread` keyword primarily in that it allows dynamic
&gt; initialization and destruction semantics. Unfortunately, this support
&gt; requires a run-time penalty for references to non-function-local
&gt; `thread_local` variables even if they don&#39;t need dynamic initialization,
&gt; so users may want to continue to use `__thread` for TLS variables with
&gt; static initialization semantics.

What is precisely the nature and origin of this run-time penalty?

Obviously to support non-function-local `thread_local` variables there needs to be a thread initialization phase before the entry to every thread main (just as there is a static initialization phase for global variables), but are they referring to some run-time penalty beyond that?

Roughly speaking what is the architecture of gcc&#39;s new implementation of thread_local?

What is the performance penalty of C++11 thread_local variables in GCC 4.8?

Can someone point out the difference between `gcc -D_FORTIFY_SOURCE=1` and `-D_FORTIFY_SOURCE=2`? I guess `=2` is more secure? I haven&#39;t been able to find a list which lists differences point by point.

I have also read that `-D_FORTIFY_SOURCE=2` should be used with `-O2`, otherwise not all features would be available. Also here i haven&#39;t found a list which would specify the regressions in detail. I would especially be interested to compile with `-Os` as the target is a device with not so much flash memory.

Any hints on where this is documented welcome!

difference between gcc -D_FORTIFY_SOURCE=1 and -D_FORTIFY_SOURCE=2

How do I printf `long long int` and also `unsigned long long int` in C99 using GCC? 

I have searched the other posts which suggest to use `%lld` but it gives these warnings:

&gt; warning#1: unknown conversion type character &#39;l&#39; in format [-Wformat]|  
&gt; warning#2: too many arguments for format [-Wformat-extra-args]|

For the following attempt:

    #include &lt;stdio.h&gt;
    
    int main()
    {
       long long int x = 0;
       unsigned long long int y = 0;
       printf(&quot;%lld\n&quot;, x);
       printf(&quot;%llu\n&quot;, y);
    }

Printf long long int in C with GCC?

I have a simple C program that forks a process and then runs an executable. 

I want to attach the child process to gdb. 

I run the main program in a console and open another console to find the pid of the child process, then I start gdb with the following command:

    gdb attach 12271

where `12271` is the child process id, but the attach fails with:

    No such file or directory.

Any idea why?


How to attach a process in gdb

I like to make GDB set a break point when a variable equal some value I set, I tried this example:

    #include &lt;stdio.h&gt;
    main()
    { 
         int i = 0;
         for(i=0;i&lt;7;++i)
            printf(&quot;%d\n&quot;, i);
    
         return 0;
    }
Output from GDB:

    (gdb) break if ((int)i == 5)
    No default breakpoint address now.
    (gdb) run
    Starting program: /home/SIFE/run 
    0
    1
    2
    3
    4
    5
    6
    
    Program exited normally.
    (gdb)

Like you see, GDB didn&#39;t make any break point, is this possible with GDB?

GDB: break if variable equal value

I have to debug a program that has errors in it as part of my assignment. However, I must first pass command line arguments in order to solve this problem.

I do:

    gdb -tui InsertionSortWithErrors

which works, but after that I don&#39;t know how to pass arguments. I used `gdb -help` and it says something about `--args` which I also tried and it didn&#39;t work.

I want to be able to get the debugger+the GUIand pass command line arguments.



How do I pass a command line argument while starting up GDB in Linux?

Suppose defined: `int a[100]`  Type `print a` then gdb will automatically display it as an array:`1, 2, 3, 4...`. However, if `a` is passed to a function as a parameter, then gdb will treat it as a normal int pointer, type `print a` will display:`(int *)0x7fffffffdaa0`. What should I do if I want to view `a` as an array?

How to view a pointer like an array in GDB?

`list` commands prints a set of lines, but I need one single line, where I am and where an error has probably occurred.



Content Type	Original Author	Original Content on Stackoverflow
Question	JohnTortugo	View Question on Stackoverflow
Solution 1 - C++	user529758	View Answer on Stackoverflow
Solution 2 - C++	pb2q	View Answer on Stackoverflow

How clear gdb command screen?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

TypeScript compiling as a single JS file

Access global page variable in helper

Attributions