check perf_map_entry for NULL.

nothing we can do but skip writing an entry, but at least _we_ won't be the cause of a crash and something that might generate an appropriate error real soon can be instead.

Author: gpshead

Python/perf_trampoline.c

@@ -208,6 +208,9 @@ perf_map_write_entry(void *state, const void *code_addr,
     }
     size_t perf_map_entry_size = snprintf(NULL, 0, "py::%s:%s", entry, filename) + 1;
     char* perf_map_entry = (char*) malloc(perf_map_entry_size);
+    if (perf_map_entry == NULL) {
+        return;
+    }
     snprintf(perf_map_entry, perf_map_entry_size, "py::%s:%s", entry, filename);
     PyUnstable_WritePerfMapEntry(code_addr, code_size, perf_map_entry);
     free(perf_map_entry);