http://llvm.org/bugs/show_bug.cgi?id=21896
Bug ID: 21896
Summary: clang-cl: Implement /Gs compiler switch
Product: clang
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Driver
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The /Gs compiler switch is ignored by clang-cl:
1>clang-cl.exe : warning : argument unused during compilation: '/Gs0x7fffffff'
1>...
1>main.obj : error LNK2019: unresolved external symbol __chkstk referenced in
function "int __cdecl mainCRTStartup(void)" (?mainCRTStartup@@YAHXZ)
The /Gs compiler switch is needed to suppress calls to __chkstk (the stack
probing function used by MSVC), e.g. when one carefully uses stack memory so
that all necessary stack probes are initiated, or when compiling with
/NODEFAULTLIB (as __chkstk would then be undefined).
One workaround could be to forward /Gs0x7fffffff or /Gs2147483647 (the maximum
value for /Gs, which is the recommended way to suppress all __chkstk() calls)
to -mno-stack-arg-probe. Currently a /Gs value of 4096 seems to be hardcoded in
LLVM:
http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709
Specifying -mno-stack-arg-probe will probably set UseStackProbe to false.
Reference:
http://msdn.microsoft.com/en-us/library/9598wk25
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