[LLVMdev] Better llvm-ld support for frameworks on Mac OS X

[Shantonu Sen]

I would like to be able to compile and link the following two program  
into native executables. These are a vastly reduced testcase, so  
ignore for a moment the fact that the native compiler driver might  
have default -L/-F search paths and -lSystem by default.

$ cat test1.c
extern char *zlibVersion(void);
extern int puts(char *);

int main(int argc, char *argv[]) {
     puts(zlibVersion());
     return 0;
}
$ clang test1.c -emit-llvm | llvm-as | llvm-ld - -native -L/usr/lib - 
lSystem -lz -v
Generating Bitcode To a.out.bc
Generating Assembly With:
'/Volumes/HD/ltmp/ssen/src/llvm/Debug/bin/llc' '-f' '-o' 'a.out.s'  
'a.out.bc'
Generating Native Executable With:
'/usr/bin/gcc' '-fno-strict-aliasing' '-O3' '-o' 'a.out' 'a.out.s' '- 
L' '/usr/lib' '-lSystem' '-lz'
ld: in /usr/lib, can't map file, errno=22
collect2: ld returned 1 exit status
llvm-ld:
$ cat test2.c
extern void *kCFRunLoopCommonModes;
extern void CFShow(void *);
int main(int argc, char *argv[]) {
     CFShow(kCFRunLoopCommonModes);
     return 0;
}
$ clang test2.c -emit-llvm | llvm-as | llvm-ld - -native -F/System/ 
Library/Frameworks -framework CoreFoundation -L/usr/lib -lSystem -v
llvm-ld: Unknown command line argument '-F/System/Library/ 
Frameworks'.  Try: 'llvm-ld --help'
llvm-ld: Unknown command line argument '-framework'.  Try: 'llvm-ld -- 
help'

There are a few issues preventing this from working. For one thing,  
although llvm-ld and the native gcc parse "-L foo" with an optional  
space, the native ld(1) linker on Mac OS X does not accept an  
intervening space, and so considers /usr/lib as an input file.

-F and -framework are not currently parsed by llvm-ld when creating  
native binaries.

The attached patch implements this functionality. Now:

$ clang test1.c -emit-llvm | llvm-as | llvm-ld - -native -L/usr/lib - 
lSystem -lz -v
Generating Bitcode To a.out.bc
Generating Assembly With:
'/Volumes/HD/ltmp/ssen/src/llvm/Debug/bin/llc' '-f' '-o' 'a.out.s'  
'a.out.bc'
Generating Native Executable With:
'/usr/bin/gcc' '-fno-strict-aliasing' '-O3' '-o' 'a.out' 'a.out.s' '-L/ 
usr/lib' '-lSystem' '-lz'
$ ./a.out
1.2.3
$ clang test2.c -emit-llvm | llvm-as | llvm-ld - -native -F/System/ 
Library/Frameworks -framework CoreFoundation -L/usr/lib -lSystem -v
Generating Bitcode To a.out.bc
Generating Assembly With:
'/Volumes/HD/ltmp/ssen/src/llvm/Debug/bin/llc' '-f' '-o' 'a.out.s'  
'a.out.bc'
Generating Native Executable With:
'/usr/bin/gcc' '-fno-strict-aliasing' '-O3' '-o' 'a.out' 'a.out.s' '-L/ 
usr/lib' '-F/System/Library/Frameworks' '-lSystem' '-framework'  
'CoreFoundation'
$ ./a.out
kCFRunLoopCommonModes

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Shantonu Sen
Apple, Inc.