[llvm] r224993 - Make the __morestack function available to the JIT memory manager under Linux.

[Reid Kleckner]

This breaks linking LLDB on Linux:

/usr/bin/ld: bin/lldb-3.6.0: hidden symbol `__morestack' in
/usr/local/google/home/rnk/gcc/install/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/libgcc.a(morestack.o)
is referenced by DSO
/usr/bin/ld: final link failed: Bad value

It also breaks building lli if you use cmake -DBUILD_SHARED_LIBS=ON.

Ideas? It's not clear to me how to reference __morestack from a DSO.

On Tue, Dec 30, 2014 at 10:06 AM, Peter Collingbourne <peter at pcc.me.uk>
wrote:

> Author: pcc
> Date: Tue Dec 30 12:06:52 2014
> New Revision: 224993
>
> URL: http://llvm.org/viewvc/llvm-project?rev=224993&view=rev
> Log:
> Make the __morestack function available to the JIT memory manager under
> Linux.
>
> This function's implementation lives in libgcc, a static library, so we
> need
> to expose it explicitly, like the other such functions.
>
> Differential Revision: http://reviews.llvm.org/D6788
>
> Modified:
>     llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp
>
> Modified: llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp?rev=224993&r1=224992&r2=224993&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp (original)
> +++ llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp Tue Dec 30
> 12:06:52 2014
> @@ -210,6 +210,10 @@ ARM_MATH_IMPORTS(ARM_MATH_DECL)
>  #undef ARM_MATH_DECL
>  #endif
>
> +#if defined(__linux__) && defined(__GLIBC__)
> +extern "C" void __morestack();
> +#endif
> +
>  uint64_t
>  RTDyldMemoryManager::getSymbolAddressInProcess(const std::string &Name) {
>    // This implementation assumes that the host program is the target.
> @@ -233,6 +237,9 @@ RTDyldMemoryManager::getSymbolAddressInP
>    if (Name == "lstat64") return (uint64_t)&lstat64;
>    if (Name == "atexit") return (uint64_t)&atexit;
>    if (Name == "mknod") return (uint64_t)&mknod;
> +
> +  // __morestack lives in libgcc, a static library.
> +  if (Name == "__morestack") return (uint64_t)&__morestack;
>  #endif // __linux__ && __GLIBC__
>
>    // See ARM_MATH_IMPORTS definition for explanation
>
>
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