Merge pull request #166 from ladyada-eagleclaw/fix-null-field-check

Check for NULL before reading an NMEA field

extras/tests/is_empty/is_empty.ino

@@ -0,0 +1,43 @@
+// Test the private field helper without changing the library's public API.
+#include <Arduino.h>
+#include <SPI.h>
+#include <Wire.h>
+#define private public
+#include <Adafruit_GPS.h>
+#undef private
+
+Adafruit_GPS GPS;
+bool testsPassed = false;
+
+void setup() {
+  Serial.begin(115200);
+  // Wait briefly for the Serial Monitor on native USB boards.
+  while (!Serial && millis() < 5000) {
+    delay(10);
+  }
+  delay(250);
+  Serial.println("Adafruit GPS NULL field regression");
+
+  char field[] = "123,";
+  if (GPS.isEmpty(field)) {
+    Serial.println("FAIL: a populated field was reported empty");
+    return;
+  }
+  Serial.println("PASS: populated field is not empty");
+
+  if (!GPS.isEmpty(NULL)) {
+    Serial.println("FAIL: a NULL field was not reported empty");
+    return;
+  }
+  Serial.println("PASS: NULL field is empty");
+  testsPassed = true;
+}
+
+void loop() {
+  if (testsPassed) {
+    Serial.println("PASS: NULL field regression");
+  } else {
+    Serial.println("FAIL: NULL field regression");
+  }
+  delay(2000);
+}

src/NMEA_parse.cpp

@@ -848,7 +848,7 @@ bool Adafruit_GPS::parseAntenna(char *p) {
 */
 /**************************************************************************/
 bool Adafruit_GPS::isEmpty(char *pStart) {
-  if (',' != *pStart && '*' != *pStart && pStart != NULL)
+  if (pStart != NULL && ',' != *pStart && '*' != *pStart)
     return false;
   else
     return true;