Potential fix for code scanning alert no. 77: Use of potentially dangerous function

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: lucasssvaz

libraries/SD_MMC/examples/SDMMC_time/SDMMC_time.ino

@@ -83,10 +83,11 @@ void listDir(fs::FS &fs, const char *dirname, uint8_t levels) {
       Serial.print("  DIR : ");
       Serial.print(file.name());
       time_t t = file.getLastWrite();
-      struct tm *tmstruct = localtime(&t);
+      struct tm tmstruct;
+      localtime_r(&t, &tmstruct);
       Serial.printf(
-        "  LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\n", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour,
-        tmstruct->tm_min, tmstruct->tm_sec
+        "  LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\n", (tmstruct.tm_year) + 1900, (tmstruct.tm_mon) + 1, tmstruct.tm_mday, tmstruct.tm_hour,
+        tmstruct.tm_min, tmstruct.tm_sec
       );
       if (levels) {
         listDir(fs, file.path(), levels - 1);
@@ -97,10 +98,11 @@ void listDir(fs::FS &fs, const char *dirname, uint8_t levels) {
       Serial.print("  SIZE: ");
       Serial.print(file.size());
       time_t t = file.getLastWrite();
-      struct tm *tmstruct = localtime(&t);
+      struct tm tmstruct;
+      localtime_r(&t, &tmstruct);
       Serial.printf(
-        "  LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\n", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour,
-        tmstruct->tm_min, tmstruct->tm_sec
+        "  LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\n", (tmstruct.tm_year) + 1900, (tmstruct.tm_mon) + 1, tmstruct.tm_mday, tmstruct.tm_hour,
+        tmstruct.tm_min, tmstruct.tm_sec
       );
     }
     file = root.openNextFile();