[Piglit] [PATCH 2/3] Use alloca instead of variable length arrays

[Jose Fonseca]

On 09/02/15 19:17, Ian Romanick wrote:
> On 02/06/2015 11:46 AM, Jose Fonseca wrote:
>> I haven't tried this sort of code with MSVC 2013 U4, but at least in the
>> past, MSVC 2013 was refusing certain kinds of variable length arrays.
>>
>> And Jan's patch is a stepping stone to -Wvla option  when compiling
>> (option which apply to the whole tree, including parts that are not
>> built with MSVC), in order to preemptively spot uses of VLA in places
>> where MSVC would break.
>
> In Mesa, we can change compiler options in subdirectories.  Is it
> possible to do this with cmake?  Like, could we remove -Wvla in
> directories that are only built on Linux?  It seems like that could give
> us the best of both worlds...

Yes, I just confirmed that MSVC 2013 U4 still fails to compile VLA code 
and was about to propose something similar.

In theory this

   string (REPLACE "-Wvla" "" CMAKE_C_FLAGS ${CMAKE_C_FLAGS})

should undo.  And it does work.  But there's a minor snafu:  this line 
must be put in the tests/spec/foo/CMakeLists.txt -- if it's put in the 
tests/spec/foo/CMakeLists.gl*.txt it has no effect --  CMAKE_C_FLAGS is 
changed, but the source files are still build with -Wvla.

(I'm always amazed that the  CMakeLists.txt -> CMakeLists.gl*.txt system 
works!)


>> So let me do the following: I'll see if MSVC 2013 accepts or refuses the
>> VLA code that caused problems the first time, and then we'll take it
>> from there.
>>
>> Jose
>

For the record these were MSVC errors:

AILED: C:\PROGRA~2\MICROS~4.0\VC\bin\cl.exe   /nologo /DWIN32 /D_WINDOWS 
/W3 /D_DEBUG /MDd /Zi /Ob0 /Od /RTC1 -I..\..\src 
-IH:\msvc32\freeglut\include -Itests\util -I..\..\tests\util 
-IH:\noarch\glext    -W3 -wd4018 -wd4244 -wd4305 -wd4800 /showIncludes 
-DGLAPIENTRY=__stdcall -DNOMINMAX -DPIGLIT_USE_GLUT 
-DPIGLIT_USE_GLUT_INIT_ERROR_FUNC -DPIGLIT_USE_OPENGL 
-DWIN32_LEAN_AND_MEAN=1 -D_CRT_NONSTDC_NO_WARNINGS 
-D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_GNU_SOURCE 
-D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_USE_MATH_DEFINES 
/Fotarget_api\gl\tests\spec\gl-1.0\CMakeFiles\gl-1.0-readpixsanity.dir\readpix.c.obj 
/Fdtarget_api\gl\tests\spec\gl-1.0\CMakeFiles\gl-1.0-readpixsanity.dir/ 
/FS -c ..\..\tests\spec\gl-1.0\readpix.c
..\..\tests\spec\gl-1.0\readpix.c(103) : error C2057: expected constant 
expression
..\..\tests\spec\gl-1.0\readpix.c(103) : error C2466: cannot allocate an 
array of constant size 0
..\..\tests\spec\gl-1.0\readpix.c(103) : error C2087: 'buf' : missing 
subscript
..\..\tests\spec\gl-1.0\readpix.c(103) : error C2133: 'buf' : unknown size
..\..\tests\spec\gl-1.0\readpix.c(200) : error C2057: expected constant 
expression
..\..\tests\spec\gl-1.0\readpix.c(200) : error C2466: cannot allocate an 
array of constant size 0
..\..\tests\spec\gl-1.0\readpix.c(200) : error C2087: 'buf' : missing 
subscript
..\..\tests\spec\gl-1.0\readpix.c(200) : error C2133: 'buf' : unknown size
..\..\tests\spec\gl-1.0\readpix.c(281) : error C2057: expected constant 
expression
..\..\tests\spec\gl-1.0\readpix.c(281) : error C2466: cannot allocate an 
array of constant size 0
..\..\tests\spec\gl-1.0\readpix.c(281) : error C2087: 'buf' : missing 
subscript
..\..\tests\spec\gl-1.0\readpix.c(281) : error C2133: 'buf' : unknown size


So there's no doubt here: by expecting a constant expression it is clear 
that MSVC does not support VLA at all.


Jose