Instead of setting compiler flags directly, you should be using a current CMake version and the [&amp;lt;LANG&amp;gt;_VISIBILITY_PRESET](https://cmake.org/cmake/help/latest/prop_tgt/LANG_VISIBILITY_PRESET.html#prop_tgt:%3CLANG%3E_VISIBILITY_PRESET) properties instead. This way you can avoid compiler specifics in your CMakeLists and improve cross platform applicability (avoiding errors such as supporting GCC and not Clang).

I.e., if you are using C++ you would either call
`set(CMAKE_CXX_VISIBILITY_PRESET hidden)` to set the property globally, or `set_target_properties(MyTarget PROPERTIES CXX_VISIBILITY_PRESET hidden)` to limit the setting to a specific library or executable target. If you are using C just replace CXX by C in the aforementioned commands. You may also want to investigate the [VISIBLITY_INLINES_HIDDEN](https://cmake.org/cmake/help/latest/prop_tgt/VISIBILITY_INLINES_HIDDEN.html) property as well.

The documentation for [GENERATE_EXPORT_HEADER](https://cmake.org/cmake/help/latest/module/GenerateExportHeader.html) includes some more tips and examples related to both properties.

You can add a flag to the Cmake compiler like that:

    set(CMAKE_C_FLAGS &quot;${CMAKE_C_FLAGS} -fvisibility=hidden&quot;)

To make sure that this only done under Linux you can use this code:

    if(UNIX AND CMAKE_COMPILER_IS_GNUCC)
        set(CMAKE_C_FLAGS &quot;${CMAKE_C_FLAGS} -fvisibility=hidden&quot;)
    endif()

I am developing a RESTful service and I want to return 400 for all unsupported URLs.

My question is **when should I choose method 1 over method 2 and vice-versa..**


    //method 1
    public ActionResult Index()
    {
        //The url is unsupported
        throw new HttpException(400, &quot;Bad Request&quot;);
    }


This one seems to be better?

    //method 2
    public ActionResult Index()
    {
        //The url is unsupported
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest, &quot;Bad Request&quot;);
    }

ASP.NET MVC, throw HttpException vs return HttpStatusCodeResult?

I would like to read a file and convert it into a base64 encoded string using the FileReader object. Here&#39;s the code I use :
&lt;pre&gt;

    var reader = new FileReader();
    reader.onloadend = function(evt) {  
        // file is loaded
        result_base64 = evt.target.result; 
    };
    reader.readAsDataURL(file); 

  
&lt;/pre&gt;

But in this case, I get the result of the conversion in the event handler (onLoadEnd event). I would like a synchronous method. Is there a way the &quot;readAsDataURL&quot; method can return directly the value of the &#39;result_base64&#39; variable ?

Read a file synchronously in Javascript

I developed cross platform software in c++. As I know, Linux .so exported all the symbols by default, well through `&quot;gcc -fvisibility=hidden&quot;` I can set all the exported symbols as hidden, then set `__attribute__(visibility(&quot;default&quot;))` for the class and function I want to export, so I can control what I want to export.

My question is, using CMake, how can I do the work as &quot;gcc -fvisibility=hidden&quot; control?

What is the CMake equivalent to &quot;gcc -fvisibility=hidden&quot; when controlling the exported symbol of a shared library?

<p>I developed cross platform software in c++. As I know, Linux .so exported all the symbols by default, well through <code>"gcc -fvisibility=hidden"</code> I can set all the exported symbols as hidden, then set <code>__attribute__(visibility("default"))</code> for the class and function I want to export, so I can control what I want to export.</p>
<p>My question is, using CMake, how can I do the work as "gcc -fvisibility=hidden" control?</p>


I have started programming practice on [codechef][1] and have been confused by the **difference between C and C99. What does C mean here? Is it C89?** Check the languages at the bottom of [this submit][2]. It contains both C and C99.

I found on the internet something called GNU C. Is there a different C for linux/unix systems? Are these compliant to the C standards by ANSI? I have also read in some places &quot;C99 strict&quot;. What is this?

Are there any other different standards of C in use? Is there something called C 4.3.2 or is it the gcc version in current use?

EDIT:&lt;br/&gt;

 [This][3], [This][4], [This][5] helped. I&#39;ll search more and edit the things that are left unanswered.

I am not a programming newbie. I know what C language is. I know that there are the different C standards by ANSI like C89, C99 and C11.


  [1]: http://www.codechef.com/problems/easy?sort_by=SuccessfulSubmission&amp;sorting_order=desc
  [2]: http://www.codechef.com/submit/TEST
  [3]: https://stackoverflow.com/a/3783805/2235567
  [4]: https://stackoverflow.com/questions/1739656/c99-backward-compatibility
  [5]: http://www.linuxquestions.org/questions/programming-9/gnu-c-and-ansi-c-520509/

What is the difference between C, C99, ANSI C and GNU C?

I&#39;m installing mingw-w64 on Windows and there are two options: win32 threads and posix threads. I know what is the difference between win32 threads and pthreads but I don&#39;t understand what is the difference between these two options. I doubt that if I will choose posix threads it will prevent me from calling WinAPI functions like CreateThread.

It seems that this option specify which threading API will be used by some program or library, but by what? By GCC, libstdc++ or by something else?

I found this:
https://stackoverflow.com/questions/13212342/whats-the-difference-between-thread-posixs-and-thread-win32-in-gcc-port-of-windo

&gt; In short, for this version of mingw, the threads-posix release will use the posix API and allow the use of std::thread, and the threads-win32 will use the win32 API, and disable the std::thread part of the standard.

Ok, if I will select win32 threads then std::thread will be unavailable but win32 threads will still be used. But used by what?

mingw-w64 threads: posix vs win32

My OS is centos which has a default gcc in path `/usr/bin/gcc`. But it is old, I need a new version of gcc. So I install a new version in a new path `/usr/local/bin/gcc`.

But when I run `cmake`, it still uses the old version gcc path(`/usr/bin/gcc`) . How can I specify the gcc to new path(`/usr/local/bin/gcc`).

I have tried to overwrite `/usr/bin/gcc` with `/usr/local/bin/gcc`, but it not work.

How to specify new GCC path for CMake

Sometimes I see someone compile a C program like this:

`gcc -o hello hello.c hello.h`

As I know, we just need to put the header files into the C program like:

`#include &quot;somefile&quot;`

and compile the C program: `gcc -o hello hello.c`.

When do we need to compile the header files or why?

Do I need to compile the header files in a C program?

I tried to implement the [C++14][1] alias template `make_integer_sequence`, which simplifies the creation of the class template [`integer_sequence`][2].

     
 

    template&lt; class T, T... I&gt; struct integer_sequence
    {
        typedef T value_type;
        static constexpr size_t size() noexcept { return sizeof...(I) ; }
    
    };
    
    template&lt; class T, T N&gt;
    using make_integer_sequence = integer_sequence&lt; T, 0,1,2, ... ,N-1 &gt;; // only for illustration.

 

   

To implement `make_integer_sequence` we need a helper structure `make_helper`.

    template&lt; class T , class N &gt;
    using make_integer_sequence = typename make_helper&lt;T,N&gt;::type;

Implementing `make_helper` isn&#39;t too difficult.


    template&lt; class T, T N, T... I &gt;
    struct make_helper
    {
       typedef typename mpl::if_&lt; T(0) == N,  
                      mpl::identity&lt; integer_sequence&lt;T,I...&gt; &gt;,
                      make_helper&lt; T, N-1, N-1,I...&gt; 
                   &gt;::type;
    };

To test `make_integer_sequence` I made this main function:


    int main()
    {
        #define GEN(z,n,temp)   \
         typedef make_integer_sequence&lt; int, n &gt;  BOOST_PP_CAT(int_seq,n) ;
    
       BOOST_PP_REPEAT(256, GEN, ~);
    }


I compiled the program with GCC 4.8.0, on a quad-core i5 system with 8GBs of RAM.
Successful compilation took 4 seconds.

But, when I changed the GEN macro to:


    int main() {
    
    #define GEN(z,n,temp) \
    typedef make_integer_sequence&lt; int, n * 4 &gt; BOOST_PP_CAT(int_seq, n) ;
    
    BOOST_PP_REPEAT(256, GEN, ~ );
    }

The compilation was unsuccessful and outputted the error message:
&gt; virtual memory exhausted.

Could somebody explain this error and what caused it?

EDIT:

I simplified the test to:

    int main()
    {
       typedef make_integer_sequence&lt; int, 4096 &gt; int_seq4096;
    }

I then successfully compiled with GCC 4.8.0 -ftemplate-depth=65536.

However this second test:

    int main()
    {
        typedef make_integer_sequence&lt; int, 16384 &gt; int_seq16384;
    }

Did not compile with GCC 4.8.0 -ftemplate-depth=65536, and resulted in the error:
&gt;virtual memory exhausted. 

So, my question is, how do I decrease template deep instantiation?

Regards,
Khurshid.

[1]: http://isocpp.org/blog/2013/05/new-paper-n3690-programming-languages-c-committee-draft
[2]: http://en.cppreference.com/w/cpp/utility/integer_sequence



Implementation C++14 make_integer_sequence

I have written a library that I used to compile using a self-written Makefile, but now I want to switch to cmake. The tree looks like this (I removed all the irrelevant files):

    .
    ├── include
    │&#160;&#160; ├── animation.h
    │&#160;&#160; ├── buffers.h
    │&#160;&#160; ├── ...
    │&#160;&#160; ├── vertex.h
    │&#160;&#160; └── world.h
    └── src
        ├── animation.cpp
        ├── buffers.cpp
        ├── ...
        ├── vertex.cpp
        └── world.cpp

So what I am trying to do is just to compile the source into a shared library and then install it with the header files.

Most examples that I have found compile executables with some shared libraries but never just a plain shared library.
It would also be helpful if someone could just tell me a very simple library that uses cmake, so I can use this as an example.

How to create a shared library with cmake?

I&#39;m not asking this for just myself. I hope this question will be a reference for the many newbies who like me, found it utterly perplexing about what exactly what was going on behind the scenes when for such a small `CMakeLists.txt` file  

    cmake_minimum_required (VERSION 2.6)
    project(Tutorial)
    add_executable(Tutorial tutorial.cpp)

and such a small `tutorial.cpp`  

    int main() { return 0; } 

 
there are so many files generated

    CMakeCache.txt  cmake_install.cmake  Makefile
    CMakeLists.txt  tutorial.cpp

and a `CMakeFiles` folder with so many files and folders  

    CMakeCCompiler.cmake               CMakeOutput.log    Makefile.cmake
    cmake.check_cache                  CMakeSystem.cmake  progress.marks
    CMakeCXXCompiler.cmake             CMakeTmp           TargetDirectories.txt
    CMakeDetermineCompilerABI_C.bin    CompilerIdC        Tutorial.dir
    CMakeDetermineCompilerABI_CXX.bin  CompilerIdCXX
    CMakeDirectoryInformation.cmake    Makefile2

Not understanding what was going on behind the scenes (i.e: why so may files had to be generated and what their purpose was), was the biggest obstacle in being able to learn CMake.  
  
If anyone knows, could you please explain it for the sake of posterity? What is the purpose of these files, and when I type `cmake .`, what exactly is cmake configuring and generating before it builds the project?

How exactly does CMake work?

# GLFW3
Last night I was working late trying to build the GLFW 3 packages for Linux from source. This process took me a very long time, about 3 hours in total, partly because I am unfamiliar with CMake, and partly because I am was unfamiliar with GLFW.
 
I hope that this post will save you from the difficulty I had yesterday! I thought I should make a short write-up, and hopefully save you several hours of your life...

Thanks to &quot;urraka&quot;, &quot;b6&quot; and &quot;niklas&quot; on the #glfw IRC channel, I have been able to get glfw version 3.0.1 working.

It turns out this is not a trivial process (certainly not for me, I am no expert) as there is not much documentation on the web about glfw3, particularly about setting it up with CMake.

I was asked to split this into a question and answer section, and so I have done that, and the answer parts are now below.

# Are you a maintainer of GLFW, or a member of the GLFW team?
If any of the maintainers of GLFW3 see this, then my message to them is please add a &quot;setting up GLFW3 on Windows, Mac OS X and Linux&quot; section to your website! It is quite easy to write programs with GLFW, since the online documentation is quite good, a quick scan of all the available classes and modules and you&#39;ll be ready to go. The example of a test project featured [here][1] is also very good. The two main problems I found were, firstly how do I set up GLFW3 on my system, and secondly how to I build a GLFW3 project? These two things perhaps aren&#39;t quite clear enough for a non-expert.

# Edit

Had a brief look today (Date: 2014-01-14) it looks as if the GLFW website has undergone heavy changes since I last looked and there is now a section on compiling GLFW and buliding programs with GLFW, which I think are new.


  [1]: http://www.glfw.org/documentation.html

How to build &amp; install GLFW 3 and use it in a Linux project

Is there a way to concatenate strings in cmake?

I have a folder that only contains .cpp files with main methods. I thought this would be easy by just using a foreach through all src files. This is what I&#39;ve got this far:

    project(opengl-tutorial)
    cmake_minimum_required(VERSION 2.8)

    aux_source_directory(. SRC_LIST)

    add_definitions(
        --std=c++11
    )

    foreach (src ${SRC_LIST})
    	# name = ${src} + &quot;.out&quot;
    	add_executable(${name} ${src})
    	target_link_libraries(${name} GL GLU GLEW glfw)
    endforeach(src ${SRC_LIST})

How can I do what&#39;s described in the comment?

How do you concatenate string in cmake

I&#39;m developing an app for iOS and I&#39;m using the Storyboard with AutoLayout ON. One of my view controllers has a set of 4 buttons, and in certain circumstances i would like to make the first one disappear.

If I use the `setHidden:TRUE` method the UIButton become invisible but it still obviously take space in the view, and the result is an &quot;hole&quot; which I&#39;ve not been able to fill making the remaining UIButton to float towards the top of the main view.

In Android I would have simply used `View.GONE` instead of `View.INVISIBLE`, but in iOS I&#39;m stuck with this behaviour and I don&#39;t want to believe that the only solution is to manually (yes I mean programmatically) move the remaining elements to the top.

I thought I would have been able to do it setting some sort of Constraint to make everything as automatic as it is in Android but I&#39;ve had no luck. 

Before I turn Autolayout OFF, can someone point me to the right direction?

I&#39;m using the IB, but I&#39;m comfortable with programmatic stuff as well.

**UPDATE:**

Setting the component height to 0 doesn&#39;t help as well.

I tried something like this:

    UIButton *b;
    CGRect frameRect = b.frame;
    frameRect.size.height = 0;
    b.frame = frameRect;


iOS equivalent for Android View.GONE visibility mode

How can I hide a column in a WPF `DataGrid` through a Binding?

This is what I did:

    &lt;DataGridTextColumn Header=&quot;Column header&quot;
                        Binding=&quot;{Binding ColumnValue}&quot;
                        Width=&quot;100&quot;
                        ElementStyle=&quot;{StaticResource DataGridRightAlign}&quot;
                        Visibility=&quot;{Binding MyColumnVisibility}&quot; /&gt;

And this is what I got (besides the column still visible):

&gt; System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=MyColumnVisibility; DataItem=null; target element is &#39;DataGridTextColumn&#39; (HashCode=1460142); target property is &#39;Visibility&#39; (type &#39;Visibility&#39;)

How to fix the binding?

Binding Visibility for DataGridColumn in WPF

I was reading about the difference between two CSS properties `display:none` and `visibility:hidden` and encountered the **DOM reflow** term.

The statement was
&gt; `display: none` causes a DOM reflow whereas `visibility: hidden` does not. 

So my question is: 
### What is DOM reflow and how does it work?

What is DOM reflow?

I tend to have a lot of these in my code

    if(shouldElementBeVisible)
        $element.show()
    else
        $element.hide()

Is there any more elegant way packaged with javascript, jquery, or underscore? Ideally I want something that looks like this

    $element.showOrHideDependingOn(shouldElementBeVisible)

Hide/show element with a boolean

In Java, we have the package protected (default) modifier for classes, which allows us to have many classes in a single package but exposes only a few and keeps the logic encapsulated.

With Kotlin this doesn&#39;t seem to be the case. If I want a few classes to be visible to each other but no further, I have to use a private modifier which limits visibility to a single file. 

So if you want 10 classes in a package but only one of them to be public, you&#39;d have to have one huge file with all the classes in it (and `private` all over the place).

Is this normal practice or there is a way to achieve some similar modularity in Kotlin?

I don&#39;t understand: if they have the notion of a package, why did they get rid of package protected access?

**Update: We might have package protected visibility after all**       
[see the discussion here][1]


  [1]: https://discuss.kotlinlang.org/t/kotlin-to-support-package-protected-visibility/1544

**Update: If you read through the discussion and still think this is a must-have feature for the language, please vote [here](https://youtrack.jetbrains.com/issue/KT-29227)** 

Content Type	Original Author	Original Content on Stackoverflow
Question	sailing	View Question on Stackoverflow
Solution 1 - Gcc	Joe	View Answer on Stackoverflow
Solution 2 - Gcc	tune2fs	View Answer on Stackoverflow

What is the CMake equivalent to "gcc -fvisibility=hidden" when controlling the exported symbol of a shared library?

Gcc Problem Overview

Gcc Solutions

Solution 1 - Gcc

Solution 2 - Gcc

Read a file synchronously in Javascript

ASP.NET MVC, throw HttpException vs return HttpStatusCodeResult?

Attributions