[sanitizer] Fix 'dyld: Symbol not found: _memmem' linkage error on Darwin 10.6

[m.ostapenko]

Summary

This patch tries to fix sanitizer linkage errors on Darwin 10.6 (GCC's pr78663 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78663).
Since I don't have Darwin target available, I'm posting original patch for GCC as it is present in GCC bugzilla to initiate further discussion.
If (ugly) ifdef stuff is not acceptable, we can probably just introduce weak hooks for mmap and munmap that will fall back to regular mmap and munmap calls accordingly. For memmem we can probably print a warning.

[kubamracek]

Maxim, I'm generally fine with this (a few nits), but 10.6 is really ancient today. We currently only support *running* (i.e. deployment target) on 10.9+, and building on 10.10+. All our Darwin buildbots (http://lab.llvm.org:8080/) are 10.10+.

I'm afraid that there will always be changes that break more and more stuff on 10.6 or even 10.7 and 10.8. If these are something that you need supported, we should get public buildbots of these configurations, and I'm afraid we can't provide them.

lib/sanitizer_common/sanitizer_mac.cc

96 ↗

(On Diff #86300)

typo "one"

107 ↗

(On Diff #86300)

clang-format please

199 ↗

(On Diff #86300)

drop the space at the start of the line

lib/sanitizer_common/sanitizer_platform_interceptors.h

51 ↗

(On Diff #86300)

drop the space between # and define

56–60 ↗

(On Diff #86300)

I don't think this is the right place for this. Can we put something like the following somewhere close to original place where SANITIZER_INTERCEPT_MEMMEM was defined:

#define SI_MAC_DEPLOYMENT_BELOW_10_7 ...
// memmem on Darwin doesn't exist on 10.6
#define SANITIZER_INTERCEPT_MEMMEM SI_NOT_WINDOWS && !SI_MAC_DEPLOYMENT_BELOW_10_7

?

[m.ostapenko]

In D29287#663079, @kubamracek wrote:

Maxim, I'm generally fine with this (a few nits), but 10.6 is really ancient today. We currently only support *running* (i.e. deployment target) on 10.9+, and building on 10.10+. All our Darwin buildbots (http://lab.llvm.org:8080/) are 10.10+.

Thank you for this information. Just to clarify: 10.6 means Darwin 10 (MACOS_VERSION_SNOW_LEOPARD), right? Because this is an original platform where linkage error occurred.

I'm afraid that there will always be changes that break more and more stuff on 10.6 or even 10.7 and 10.8. If these are something that you need supported, we should get public buildbots of these configurations, and I'm afraid we can't provide them.

Okay, got it, we'll probably need to disable sanitizers on Darwin 10 and older in future GCC releases (or just fix problems locally).

[kubamracek]

Thank you for this information. Just to clarify: 10.6 means Darwin 10 (MACOS_VERSION_SNOW_LEOPARD), right? Because this is an original platform where linkage error occurred.

Correct, macOS 10.6 is Snow Leopard.

[m.ostapenko]

Updating according to Kuba's nits.

compiler-rt/trunk/lib/sanitizer_common/sanitizer_mac.cc

extern kern_return_t mach_vm_region_recurse(
     vm_region_recurse_info_t info,
     mach_msg_type_number_t *infoCnt);
 }
 
 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) {
   return mprotect(addr, length, prot);
 }
 
 uptr internal_close(fd_t fd) {
   return close(fd);

 
 void internal_sigfillset(__sanitizer_sigset_t *set) { sigfillset(set); }
 
 uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
                           __sanitizer_sigset_t *oldset) {
   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() {
+  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);
     return -1;
   }
   if (pid == 0) {
     close(master);
     if (login_tty(slave) != 0) {

compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h

 #define SANITIZER_INTERCEPT_STRSPN 1
 #define SANITIZER_INTERCEPT_STRPBRK 1
 #define SANITIZER_INTERCEPT_TEXTDOMAIN SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_STRCASECMP SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_MEMSET 1
 #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
 
 #define SANITIZER_INTERCEPT_READ   SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_PREAD  SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_WRITE  SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_PWRITE SI_NOT_WINDOWS