diff --git a/compiler-rt/lib/asan/asan_report.cpp b/compiler-rt/lib/asan/asan_report.cpp
--- a/compiler-rt/lib/asan/asan_report.cpp
+++ b/compiler-rt/lib/asan/asan_report.cpp
@@ -160,6 +160,9 @@
       BlockingMutexLock l(&error_message_buf_mutex);
       internal_memcpy(buffer_copy.data(),
                       error_message_buffer, kErrorMessageBufferSize);
+      // Clear error_message_buffer so that if we find other errors
+      // we don't re-log this error.
+      error_message_buffer_pos = 0;
     }
 
     LogFullErrorReport(buffer_copy.data());
diff --git a/compiler-rt/test/asan/TestCases/Darwin/duplicate_os_log_reports.cpp b/compiler-rt/test/asan/TestCases/Darwin/duplicate_os_log_reports.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Darwin/duplicate_os_log_reports.cpp
@@ -0,0 +1,68 @@
+// UNSUPPORTED: ios
+// REQUIRES: shell
+// REQUIRES: darwin_log_cmd
+// RUN: %clangxx_asan -fsanitize-recover=address %s -o %t
+// RUN: { %env_asan_opts=halt_on_error=0,log_to_syslog=1 %run %t > %t.process_output.txt 2>&1 & } \
+// RUN: ; export TEST_PID=$! ; wait ${TEST_PID}
+
+// Check process output.
+// RUN: FileCheck %s --check-prefixes CHECK,CHECK-PROC -input-file=%t.process_output.txt
+
+// Check syslog output. We filter recent system logs based on PID to avoid
+// getting the logs of previous test runs.
+// RUN: log show --debug --last 2m  --predicate "processID == ${TEST_PID}" --style syslog > %t.process_syslog_output.txt
+// RUN: FileCheck %s -input-file=%t.process_syslog_output.txt
+#include <cassert>
+#include <cstdio>
+#include <sanitizer/asan_interface.h>
+
+const int kBufferSize = 512;
+char *buffer;
+
+// `readZero` and `readOne` exist so that we can distinguish the two
+// error reports based on the symbolized stacktrace.
+void readZero() {
+  assert(__asan_address_is_poisoned(buffer));
+  char c = buffer[0];
+  printf("Read %c\n", c);
+}
+
+void readOne() {
+  assert(__asan_address_is_poisoned(buffer + 1));
+  char c = buffer[1];
+  printf("Read %c\n", c);
+}
+
+int main() {
+  buffer = static_cast<char *>(malloc(kBufferSize));
+  assert(buffer);
+  // Deliberately poison `buffer` so that we have a deterministic way
+  // triggering two ASan reports in a row in the no halt_on_error mode (e.g. Two
+  // heap-use-after free in a row might not be deterministic).
+  __asan_poison_memory_region(buffer, kBufferSize);
+
+  // This sequence of ASan reports are designed to catch an old bug in the way
+  // ASan's internal syslog buffer was handled after reporting an issue.
+  // Previously in the no halt_on_error mode the internal buffer wasn't cleared
+  // after reporting an issue. When another issue was encountered everything
+  // that was already in the buffer would be written to the syslog again
+  // leading to duplicate reports in the syslog.
+
+  // First bad access.
+  // CHECK: use-after-poison
+  // CHECK-NEXT: READ of size 1
+  // CHECK-NEXT: #0 0x{{[0-9a-f]+}} in readZero
+  // CHECK: SUMMARY: {{.*}} use-after-poison {{.*}} in readZero
+  readZero();
+
+  // Second bad access.
+  // CHECK: use-after-poison
+  // CHECK-NEXT: READ of size 1
+  // CHECK-NEXT: #0 0x{{[0-9a-f]+}} in readOne
+  // CHECK: SUMMARY: {{.*}} use-after-poison {{.*}} in readOne
+  readOne();
+
+  // CHECK-PROC: DONE
+  printf("DONE\n");
+  return 0;
+}
diff --git a/compiler-rt/test/lit.common.cfg.py b/compiler-rt/test/lit.common.cfg.py
--- a/compiler-rt/test/lit.common.cfg.py
+++ b/compiler-rt/test/lit.common.cfg.py
@@ -533,6 +533,10 @@
   # much slower. Let's override this and run lit tests with 'abort_on_error=0'.
   config.default_sanitizer_opts += ['abort_on_error=0']
   config.default_sanitizer_opts += ['log_to_syslog=0']
+  if lit.util.which('log'):
+    config.available_features.add('darwin_log_cmd')
+  else:
+    lit_config.warning('log command not found. Some tests will be skipped.')
 elif config.android:
   config.default_sanitizer_opts += ['abort_on_error=0']