Merge pull request #1223 from ElijahPepe:fix/implement-snprintf-safely

PiperOrigin-RevId: 463581990
Change-Id: I47359d4d2d2fcd2365b5ff9a5c3b61b5751e4ed2

absl/synchronization/mutex.cc

@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <atomic>
 #include <cinttypes>
+#include <cstddef>
 #include <thread>  // NOLINT(build/c++11)
 
 #include "absl/base/attributes.h"
@@ -430,7 +431,11 @@ static void PostSynchEvent(void *obj, int ev) {
     char buffer[ABSL_ARRAYSIZE(pcs) * 24];
     int pos = snprintf(buffer, sizeof (buffer), " @");
     for (int i = 0; i != n; i++) {
-      pos += snprintf(&buffer[pos], sizeof (buffer) - pos, " %p", pcs[i]);
+      int b = snprintf(&buffer[pos], sizeof(buffer) - pos, " %p", pcs[i]);
+      if (b < 0 || static_cast<size_t>(b) >= sizeof(buffer) - pos) {
+        break;
+      }
+      pos += b;
     }
     ABSL_RAW_LOG(INFO, "%s%p %s %s", event_properties[ev].msg, obj,
                  (e == nullptr ? "" : e->name), buffer);