[Piglit] [PATCH] mingw: use default 2MB stack size instead of 1MB

[Jose Fonseca]

The intent here was not so much to match the piglti MSVC build, but apps 
build by MSVC in general.

After all, nothing ever prevented us from setting a huge stack size on 
both MinGW and MSVC alike, as both toolchains allow to congifure the 
stack size to whatever we want.


The key issue here is that OpenGL driver don't get to pick the apps they 
are loaded, and real OpenGL applications will be likely built with MSVC 
instead of Mingw, and therefore will likely only have the MSVC default 
stack size.  And we should err on the side of caution when testing.


Regardless of the compiler used, if we bump the stack size in piglit, 
one is just increasing the chance that wasteful stack allocations go 
undetected on piglit and blow up on real applications.


Therefore I suggest we continue to keep 1MB default, and try to fix Mesa 
to be less stack hungry.   If that's not pratical here, then we should 
try to bump the stack size of specific piglit tests (like those that 
stress the compiler to the extreme, as Cmake allows to set these options 
per executable), and only those tests.  Or just mark the affected tests 
as expected fail/skip.


If we feel that 1MB stack is too restrictive nowadays, then we should 
invest time into moving GLSL compilation into a separate/internal 
thread, which would enable us to pick whatever stack size we want when 
creating that thread.  Another alternative is to do a low-level 
manipulation of stack registers, and force the compilation to happen in 
manually allocated stack.   Neither are easy-peasy though, and severaly 
hamper debugability.

Jose

On 12/10/17 14:43, Brian Paul wrote:
> The op-selection-bool-bvec4-bvec4.frag test has an expression which
> adds 512 terms.  This causes 512 levels of recursion in Mesa's
> ir_expression::constant_expression_value() function.  Since each
> function activation record is about 2KB in size with MSVC, this
> causes us to overflow the stack and crash.
> 
> The crash was only recently exposed with MSVC 2015 debug builds of Mesa.
> 
> The default MinGW stack size of 2MB is enough to avoid this issue.
> Since we no longer build Piglit with MSVC, we don't have to match
> MSVC's 1MB stack default.
> ---
>   CMakeLists.txt | 3 ---
>   1 file changed, 3 deletions(-)
> 
> diff --git a/CMakeLists.txt b/CMakeLists.txt
> index 4259ec8..cdecca4 100644
> --- a/CMakeLists.txt
> +++ b/CMakeLists.txt
> @@ -301,9 +301,6 @@ else ()
>   endif ()
>   
>   if (MINGW)
> -	# Match MSVC default stack size
> -	set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--stack,1048576")
> -
>   	# Avoid depending on MinGW runtime DLLs
>   	check_cxx_compiler_flag (-static-libgcc HAVE_STATIC_LIBGCC_FLAG)
>   	if (HAVE_STATIC_LIBGCC_FLAG)
>