simple assignment statement compiles but becomes a run time error

[Mike Parker via Digitalmars-d-learn]

On 1/19/2015 10:44 AM, WhatMeWorry wrote:
> On Sunday, 18 January 2015 at 20:07:25 UTC, weaselcat wrote:
>> On Sunday, 18 January 2015 at 19:51:02 UTC, WhatMeWorry wrote:
>>> On Sunday, 18 January 2015 at 19:42:33 UTC, WhatMeWorry wrote:
>>>>
>>>> I've got a OpenGL function returning a pointer
>>>>
>>>> // const GLubyte *version = glGetString(GL_VERSION);  // C++ and
>>>> openLG code
>>>>
>>>> // the following compiles with no errors or warnings
>>>>
>>>> char openglVersion[100] = fromStringz(glGetString(GL_VERSION));
>>>> // ABENDS HERE!
>>>>
>>>>
>>>> // documentation from std.string shows
>>>> // pure @system inout(char)[] fromStringz(inout(char)* cString);
>>>>
>>>> // Seems pretty innocuous to me.
>>>>
>>>>
>>>> Debugger returns:
>>>> Unhandled exception at 0x76AC2F71 (KernelBase.dll) in
>>>> WhatVersionOfOpenGL.exe
>>
>> Hi,
>>
>> try replacing the fromStringz with to!string from std.conv
>
> No cigar.
>
> char openglVersion[100] = fromStringz(glGetString(GL_VERSION));
> causes the same exception.
>
> Thanks for suggestion.  Could (Can?) OpenGL be marking the string as
> read only?  So we can print out value put not copy it?
>
>

You're trying to shove a dynamic array into a static array. That isn't 
going to fly. Your openglVersion variable needs to be dynamic. Declare 
it as "string" or "auto":

auto openglVersion = fromStringz( glGetString( GL_Version ));

Note that fromStringz returns a slice of the C string, which means that 
if the C string doesn't survive after the return call, or if you plan to 
keep your D string around outside of the call site, you can get a crash. 
The OpenGL specification requires strings returned by glGetString to be 
static, i.e. the pointer will always be valid, so you can do whatever 
you want. Generally, though, to!string is what you want. It allocates 
memory for the string and copies it.