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Fixed bug 5366 - cmake build doesn't detect Metal on macOS 

Tom Seddon

2nd time lucky, perhaps. patch 2 applies to current HEAD at time of writing - 4eb049c9bb1ca94efe3c40b57beda3169984d0cb from https://github.com/SDL-mirror/SDL.

This basically goes back to what was there originally, but now manually adding "-x objective-c" to the clang command line rather than "-ObjC". clang is then invoked without the "-x c" that was causing the problem, the snippet builds, and Metal is detected. (I had a quick trawl through the cmake code, but I couldn't see where this is handled.)

I was moved to try this after finding SDL's own CHECK_OBJC_SOURCE_COMPILES macro, and noting what it does: 4eb049c9bb/cmake/macros.cmake (L67)

An alternative fix of course would be to use CHECK_OBJC_SOURCE_COMPILES instead of cmake's check_objc_source_compiles - but that had the same problem of getting confused by "return 0;". (Maybe that's because it's a macro? I'll defer to a cmake expert on this one.)

I decided in the end to err on the side of leaving things looking basically the same as they were before my first patch.
This commit is contained in:
Sam Lantinga 2020-12-09 06:17:55 -08:00
parent 475405e036
commit 42c5b4acde
1 changed files with 5 additions and 2 deletions
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7
CMakeLists.txt
View File

@ -32,7 +32,6 @@ include(CheckIncludeFiles)
include(CheckIncludeFile) include(CheckIncludeFile)
include(CheckSymbolExists) include(CheckSymbolExists)
include(CheckCSourceCompiles) include(CheckCSourceCompiles)
include(CheckOBJCSourceCompiles)
include(CheckCSourceRuns) include(CheckCSourceRuns)
include(CheckCCompilerFlag) include(CheckCCompilerFlag)
include(CheckTypeSize) include(CheckTypeSize)
@ -1802,7 +1801,9 @@ elseif(APPLE)
endif() endif()
if(VIDEO_VULKAN OR VIDEO_METAL OR RENDER_METAL) if(VIDEO_VULKAN OR VIDEO_METAL OR RENDER_METAL)
check_objc_source_compiles(" set(ORIG_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "-x objective-c ${CMAKE_REQUIRED_FLAGS}")
check_c_source_compiles("
#include <AvailabilityMacros.h> #include <AvailabilityMacros.h>
#import <Metal/Metal.h> #import <Metal/Metal.h>
#import <QuartzCore/CAMetalLayer.h> #import <QuartzCore/CAMetalLayer.h>
@ -1812,8 +1813,10 @@ elseif(APPLE)
#endif #endif
int main() int main()
{ {
return 0;
} }
" HAVE_FRAMEWORK_METAL) " HAVE_FRAMEWORK_METAL)
set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
if(HAVE_FRAMEWORK_METAL) if(HAVE_FRAMEWORK_METAL)
set(SDL_FRAMEWORK_METAL 1) set(SDL_FRAMEWORK_METAL 1)
set(SDL_FRAMEWORK_QUARTZCORE 1) set(SDL_FRAMEWORK_QUARTZCORE 1)