Don't include backtraces in syncDebug CRCs.

This should allow using syncDebugBacktrace() without causing a desynch if some clients don't support them or print them differently.

lib/netplay/netplay.c

@@ -3000,8 +3000,10 @@ void _syncDebug(const char *function, const char *str, ...)
 	}
 }
 
-void syncDebugBacktrace(void)
+void _syncDebugBacktrace(const char *function)
 {
+	uint32_t backupCrc = syncDebugCrcs[syncDebugNext];  // Ignore CRC changes from _syncDebug(), since identical backtraces can be printed differently.
+
 #ifdef WZ_OS_LINUX
 	void *btv[20];
 	unsigned num = backtrace(btv, sizeof(btv)/sizeof(*btv));
@@ -3013,8 +3015,11 @@ void syncDebugBacktrace(void)
 	}
 	free(btc);
 #else
-	_syncDebug("BT", "Sorry, syncDebugBacktrace() not implemented on your system.");
+	_syncDebug("BT", "Sorry, syncDebugBacktrace() not implemented on your system. Called from %s.", function);
 #endif
+
+	// Use CRC of something platform-independent, to avoid false positive desynchs.
+	syncDebugCrcs[syncDebugNext] = crcSum(backupCrc, function, strlen(function) + 1);
 }
 
 static void clearSyncDebugNext(void)

lib/netplay/netplay.h

@@ -364,7 +364,8 @@ const char *messageTypeToString(unsigned messageType);
 #define syncDebug(...) do { _syncDebug(__FUNCTION__, __VA_ARGS__); } while(0)
 void _syncDebug(const char *function, const char *str, ...)
 	WZ_DECL_FORMAT(printf, 2, 3);
-void syncDebugBacktrace(void);  ///< Adds a backtrace to syncDebug. (Expect lots of false positives, if all clients aren't using the exact same binaries.)
+#define syncDebugBacktrace() do { _syncDebugBacktrace(__FUNCTION__); } while(0)
+void _syncDebugBacktrace(const char *function);                  ///< Adds a backtrace to syncDebug, if the platform supports it. Can be a bit slow, don't call way too often, unless desperate.
 
 void resetSyncDebug(void);                                       ///< Resets the syncDebug, so syncDebug from a previous game doesn't cause a spurious desynch dump.
 uint32_t nextDebugSync(void);                                    ///< Returns a CRC corresponding to all syncDebug() calls since the last nextDebugSync() or resetSyncDebug() call.