[asan] Delay system log initialization on Android.

Writing to system log requires libc interceptors to be initialized.
Fixes crashes with verbosity=1 on newer Android builds.

llvm-svn: 217764

compiler-rt/lib/asan/asan_rtl.cc

@@ -592,6 +592,11 @@ static void AsanInitInternal() {
 
   InitializeAsanInterceptors();
 
+  // Enable system log ("adb logcat") on Android.
+  // Doing this before interceptors are initialized crashes in:
+  // AsanInitInternal -> android_log_write -> __interceptor_strcmp
+  AndroidLogInit();
+
   ReplaceSystemMalloc();
 
   uptr shadow_start = kLowShadowBeg;

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -544,10 +544,13 @@ F IndirectExternCall(F f) {
 #endif
 
 #if SANITIZER_ANDROID
+// Initialize Android logging. Any writes before this are silently lost.
+void AndroidLogInit();
 void AndroidLogWrite(const char *buffer);
 void GetExtraActivationFlags(char *buf, uptr size);
 void SanitizerInitializeUnwinder();
 #else
+INLINE void AndroidLogInit() {}
 INLINE void AndroidLogWrite(const char *buffer_unused) {}
 INLINE void GetExtraActivationFlags(char *buf, uptr size) { *buf = '\0'; }
 INLINE void SanitizerInitializeUnwinder() {}

compiler-rt/lib/sanitizer_common/sanitizer_linux.cc

@@ -836,11 +836,19 @@ uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
 #endif  // defined(__x86_64__) && SANITIZER_LINUX
 
 #if SANITIZER_ANDROID
+static atomic_uint8_t android_log_initialized;
+
+void AndroidLogInit() {
+  atomic_store(&android_log_initialized, 1, memory_order_release);
+}
 // This thing is not, strictly speaking, async signal safe, but it does not seem
 // to cause any issues. Alternative is writing to log devices directly, but
 // their location and message format might change in the future, so we'd really
 // like to avoid that.
 void AndroidLogWrite(const char *buffer) {
+  if (!atomic_load(&android_log_initialized, memory_order_acquire))
+    return;
+
   char *copy = internal_strdup(buffer);
   char *p = copy;
   char *q;