[PATCH][PR sanitizer/78663] Fix 'dyld: Symbol not found: _memmem' linkage error on Darwin 10.6.

[Maxim Ostapenko]

Hi,

this patch fixes  'dyld: Symbol not found: _memmem' linkage error on 
Darwin 10.6.
Just cherry-pick r293992 from upstream, OK to apply?
-Maxim
libsanitizer/ChangeLog:

2017-02-03  Maxim Ostapenko  <m.ostape...@samsung.com>

	PR sanitizer/78663
	* sanitizer_common/sanitizer_mac.cc: Cherry-pick upstream r293992.
	* sanitizer_common/sanitizer_platform_interceptors.h: Likewise.

diff --git a/libsanitizer/sanitizer_common/sanitizer_mac.cc b/libsanitizer/sanitizer_common/sanitizer_mac.cc
index 62be7b0..2a05102 100644
--- a/libsanitizer/sanitizer_common/sanitizer_mac.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_mac.cc
@@ -91,20 +91,22 @@ namespace __sanitizer {
 
 #include "sanitizer_syscall_generic.inc"
 
-// Direct syscalls, don't call libmalloc hooks.
+// Direct syscalls, don't call libmalloc hooks (but not available on 10.6).
 extern "C" void *__mmap(void *addr, size_t len, int prot, int flags, int fildes,
-                        off_t off);
-extern "C" int __munmap(void *, size_t);
+                        off_t off) SANITIZER_WEAK_ATTRIBUTE;
+extern "C" int __munmap(void *, size_t) SANITIZER_WEAK_ATTRIBUTE;
 
 // ---------------------- sanitizer_libc.h
 uptr internal_mmap(void *addr, size_t length, int prot, int flags,
                    int fd, u64 offset) {
   if (fd == -1) fd = VM_MAKE_TAG(VM_MEMORY_ANALYSIS_TOOL);
-  return (uptr)__mmap(addr, length, prot, flags, fd, offset);
+  if (__mmap) return (uptr)__mmap(addr, length, prot, flags, fd, offset);
+  return (uptr)mmap(addr, length, prot, flags, fd, offset);
 }
 
 uptr internal_munmap(void *addr, uptr length) {
-  return __munmap(addr, length);
+  if (__munmap) return __munmap(addr, length);
+  return munmap(addr, length);
 }
 
 int internal_mprotect(void *addr, uptr length, int prot) {
@@ -190,17 +192,19 @@ uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
   return sigprocmask(how, set, oldset);
 }
 
-// Doesn't call pthread_atfork() handlers.
-extern "C" pid_t __fork(void);
+// Doesn't call pthread_atfork() handlers (but not available on 10.6).
+extern "C" pid_t __fork(void) SANITIZER_WEAK_ATTRIBUTE;
 
 int internal_fork() {
-  return __fork();
+  if (__fork)
+    return __fork();
+  return fork();
 }
 
 int internal_forkpty(int *amaster) {
   int master, slave;
   if (openpty(&master, &slave, nullptr, nullptr, nullptr) == -1) return -1;
-  int pid = __fork();
+  int pid = internal_fork();
   if (pid == -1) {
     close(master);
     close(slave);
diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h b/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h
index 2a88605..6b2ba31 100644
--- a/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h
+++ b/libsanitizer/sanitizer_common/sanitizer_platform_interceptors.h
@@ -81,8 +81,16 @@
 #define SANITIZER_INTERCEPT_MEMMOVE 1
 #define SANITIZER_INTERCEPT_MEMCPY 1
 #define SANITIZER_INTERCEPT_MEMCMP 1
+#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && \
+    __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1070
+# define SI_MAC_DEPLOYMENT_BELOW_10_7 1
+#else
+# define SI_MAC_DEPLOYMENT_BELOW_10_7 0
+#endif
+// memmem on Darwin doesn't exist on 10.6
 // FIXME: enable memmem on Windows.
-#define SANITIZER_INTERCEPT_MEMMEM SI_NOT_WINDOWS
+#define SANITIZER_INTERCEPT_MEMMEM \
+  SI_NOT_WINDOWS && !SI_MAC_DEPLOYMENT_BELOW_10_7
 #define SANITIZER_INTERCEPT_MEMCHR 1
 #define SANITIZER_INTERCEPT_MEMRCHR SI_FREEBSD || SI_LINUX