[libunwind] Define and use portable macro for checking for presence of ASAN

[daniel-levin]

Summary

• libunwind does not build with GCC due to a change introduced in adf1561d6ce8 which uses the clang-only __has_feature macro.
• The problem is resolved by defining an "Is asan present?" macro that works across different compilers

[daniel-levin]

Hi all :)

I am new to contributing to LLVM. This change fixes a broken build when bootstrapping with gcc. Both gcc and msvc define the SANITIZE_ADDRESS macro when using asan.

Please give me any and all feedback. I am happy to make changes.

[compnerd]

libunwind/src/libunwind.cpp

25

I think that I would rather see this as:

#if !defined(__has_feature)
#define __has_feature(feature) 0
#endif

Then you can use # if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__) below.

That along with a comment would be sufficient. The GCC check would still be insufficient as it doesn't cover KASAN, but I don't believe that GCC supports that currently.

[daniel-levin]

[libunwind] Use most appropriate macro for checking for presence of ASan.

[daniel-levin]

Responded to comments from Saleem. Apologies for the noise in getting the diff correct. I had not used arc before.

[compnerd]

LGTM; do you need someone to commit this on your behalf?

[daniel-levin]

Yes please. I do not have commit access. Thank you Saleem :)

libunwind/src/libunwind.cpp

 
 #include <libunwind.h>
 
 #include "libunwind_ext.h"
 #include "config.h"
 
 #include <stdlib.h>
 
-#if __has_feature(address_sanitizer)
+// Define the __has_feature extension for compilers that do not support it so
+// that we can later check for the presence of ASan in a compiler-neutral way.
+#if !defined(__has_feature)
+#define __has_feature(feature) 0
+#endif
+
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
 #include <sanitizer/asan_interface.h>
 #endif
 
 #if !defined(__USING_SJLJ_EXCEPTIONS__)
 #include "AddressSpace.hpp"
 #include "UnwindCursor.hpp"
 
 using namespace libunwind;
if (info->end_ip == 0)
     return UNW_ENOINFO;
   return UNW_ESUCCESS;
 }
 _LIBUNWIND_WEAK_ALIAS(__unw_get_proc_info, unw_get_proc_info)
 
 /// Resume execution at cursor position (aka longjump).
 _LIBUNWIND_HIDDEN int __unw_resume(unw_cursor_t *cursor) {
   _LIBUNWIND_TRACE_API("__unw_resume(cursor=%p)", static_cast<void *>(cursor));
-#if __has_feature(address_sanitizer)
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
   // Inform the ASan runtime that now might be a good time to clean stuff up.
   __asan_handle_no_return();
 #endif
   AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
   co->jumpto();
   return UNW_EUNSPEC;
 }
 _LIBUNWIND_WEAK_ALIAS(__unw_resume, unw_resume)