[libFuzzer] Break dependency on common_interface_defs.h

[morehouse]

Summary

Some libFuzzer users build using the build.sh script, without access to
the <sanitizer/common_interface_defs.h> include.

Update https://github.com/rust-fuzz/libfuzzer/issues/65.

[dokyungs]

LGTM

compiler-rt/lib/fuzzer/FuzzerInterceptors.cpp

#define DEFINE_REAL(ret_type, func, ...)                                       \
   typedef ret_type (*FUNC_TYPE(func))(__VA_ARGS__);                            \
   namespace __interception {                                                   \
   FUNC_TYPE(func) PTR_TO_REAL(func);                                           \
   }
 
 #include <cassert>
 #include <cstdint>
 #include <dlfcn.h> // for dlsym()
-#include <sanitizer/common_interface_defs.h>
 
 static void *getFuncAddr(const char *name, uintptr_t wrapper_addr) {
   void *addr = dlsym(RTLD_NEXT, name);
   if (!addr) {
     // If the lookup using RTLD_NEXT failed, the sanitizer runtime library is
     // later in the library search order than the DSO that we are trying to
     // intercept, which means that we cannot intercept this function. We still
     // want the address of the real definition, though, so look it up using
for (size_t pos = 0; pos <= len1 - len2; pos++) {
     if (internal_memcmp(haystack + pos, needle, len2) == 0)
       return const_cast<char *>(haystack) + pos;
   }
   return nullptr;
 }
 
 extern "C" {
 
+// Weak hooks forward-declared to avoid dependency on
+// <sanitizer/common_interface_defs.h>.
+void __sanitizer_weak_hook_memcmp(void *called_pc, const void *s1,
+                                  const void *s2, size_t n, int result);
+void __sanitizer_weak_hook_strncmp(void *called_pc, const char *s1,
+                                   const char *s2, size_t n, int result);
+void __sanitizer_weak_hook_strncasecmp(void *called_pc, const char *s1,
+                                       const char *s2, size_t n, int result);
+void __sanitizer_weak_hook_strcmp(void *called_pc, const char *s1,
+                                  const char *s2, int result);
+void __sanitizer_weak_hook_strcasecmp(void *called_pc, const char *s1,
+                                      const char *s2, int result);
+void __sanitizer_weak_hook_strstr(void *called_pc, const char *s1,
+                                  const char *s2, char *result);
+void __sanitizer_weak_hook_strcasestr(void *called_pc, const char *s1,
+                                      const char *s2, char *result);
+void __sanitizer_weak_hook_memmem(void *called_pc, const void *s1, size_t len1,
+                                  const void *s2, size_t len2, void *result);
+
 DEFINE_REAL(int, bcmp, const void *, const void *, size_t)
 DEFINE_REAL(int, memcmp, const void *, const void *, size_t)
 DEFINE_REAL(int, strncmp, const char *, const char *, size_t)
 DEFINE_REAL(int, strcmp, const char *, const char *)
 DEFINE_REAL(int, strncasecmp, const char *, const char *, size_t)
 DEFINE_REAL(int, strcasecmp, const char *, const char *)
 DEFINE_REAL(char *, strstr, const char *, const char *)
 DEFINE_REAL(char *, strcasestr, const char *, const char *)