Bail out on a zero-sized buffer and cast err for %ld

snprintf writes nothing at all when bufsz is 0, not even a terminator, so the
checksum helper would run strchr over whatever the buffer already held. Return
before touching it.

int32_t is not long on every target, so cast before formatting with %ld.

Co-Authored-By: Andrew Yong <me@ndoo.sg>

Author: caveman99

src/gps/NMEAWPL.cpp

@@ -40,6 +40,9 @@ static uint32_t nmeaChecksum(const char *buf)
 
 uint32_t printWPL(char *buf, size_t bufsz, const meshtastic_PositionLite &pos, const char *name, bool isCaltopoMode)
 {
+    if (bufsz == 0)
+        return 0;
+
     GeoCoord geoCoord(pos.latitude_i, pos.longitude_i, pos.altitude);
     char type = isCaltopoMode ? 'P' : 'N';
     uint32_t len = snprintf(buf, bufsz, "\r\n$G%cWPL,%02d%07.4f,%c,%03d%07.4f,%c,%s", type, geoCoord.getDMSLatDeg(),
@@ -54,6 +57,9 @@ uint32_t printWPL(char *buf, size_t bufsz, const meshtastic_PositionLite &pos, c
 
 uint32_t printWPL(char *buf, size_t bufsz, const meshtastic_Position &pos, const char *name, bool isCaltopoMode)
 {
+    if (bufsz == 0)
+        return 0;
+
     GeoCoord geoCoord(pos.latitude_i, pos.longitude_i, pos.altitude);
     char type = isCaltopoMode ? 'P' : 'N';
     uint32_t len = snprintf(buf, bufsz, "$G%cWPL,%02d%07.4f,%c,%03d%07.4f,%c,%s", type, geoCoord.getDMSLatDeg(),
@@ -89,6 +95,9 @@ uint32_t printWPL(char *buf, size_t bufsz, const meshtastic_Position &pos, const
 
 uint32_t printGGA(char *buf, size_t bufsz, const meshtastic_Position &pos)
 {
+    if (bufsz == 0)
+        return 0;
+
     GeoCoord geoCoord(pos.latitude_i, pos.longitude_i, pos.altitude);
     time_t timestamp = pos.timestamp;
 

src/platform/stm32wl/STM32_LittleFS.cpp

@@ -273,7 +273,7 @@ const char *dbg_strerr_lfs(int32_t err)
 
     default:
         static char errcode[13];
-        snprintf(errcode, sizeof(errcode), "%ld", err);
+        snprintf(errcode, sizeof(errcode), "%ld", (long)err);
         return errcode;
     }