Make sanitizers' interceptors non-weak on FreeBSD

[kutuzov.viktor.84]

Summary

Related discussion:
http://docs.freebsd.org/cgi/getmsg.cgi?fetch=16483939+0+current/freebsd-current

[kcc]

lib/interception/interception.h

154

shouldn't we have #elif (FreeBSD) on the same level as other OSes (APPLE, _WIN32)?

[kutuzov.viktor.84]

Reworked so that the Linux and FreeBSD clauses do not share definitions.

[kcc]

LGTM

[kutuzov.viktor.84]

Closed by commit rL212693 (authored by vkutuzov).

lib/interception/interception.h

 #  define WRAP(x) __asan_wrap_##x
 #  define WRAPPER_NAME(x) "__asan_wrap_"#x
 #  define INTERCEPTOR_ATTRIBUTE __declspec(dllexport)
 # endif
 # define DECLARE_WRAPPER(ret_type, func, ...) \
     extern "C" ret_type func(__VA_ARGS__);
 # define DECLARE_WRAPPER_WINAPI(ret_type, func, ...) \
     extern "C" __declspec(dllimport) ret_type __stdcall func(__VA_ARGS__);
+#elif defined(__FreeBSD__)
+# define WRAP(x) __interceptor_ ## x
+# define WRAPPER_NAME(x) "__interceptor_" #x
+# define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
+// FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher
+// priority than weak ones so weak aliases won't work for indirect calls
+// in position-independent (-fPIC / -fPIE) mode.
+# define DECLARE_WRAPPER(ret_type, func, ...) \
+     extern "C" ret_type func(__VA_ARGS__) \
+     __attribute__((alias("__interceptor_" #func), visibility("default")));
 #else
 # define WRAP(x) __interceptor_ ## x
 # define WRAPPER_NAME(x) "__interceptor_" #x
 # define INTERCEPTOR_ATTRIBUTE __attribute__((visibility("default")))
 # define DECLARE_WRAPPER(ret_type, func, ...) \
     extern "C" ret_type func(__VA_ARGS__) \
     __attribute__((weak, alias("__interceptor_" #func), visibility("default")));
 #endif
 
 #if !defined(__APPLE__)
 # define PTR_TO_REAL(x) real_##x
 # define REAL(x) __interception::PTR_TO_REAL(x)
 # define FUNC_TYPE(x) x##_f
 
 # define DECLARE_REAL(ret_type, func, ...) \