Use a Defer struct to close files and restore lexer state with RAII (#1379)

src/link/output.cpp

@@ -199,6 +199,10 @@ static void writeROM() {
 		if (!outputFile)
 			err("Failed to open output file \"%s\"", outputFileName);
 	}
+	Defer closeOutputFile{[&] {
+		if (outputFile)
+			fclose(outputFile);
+	}};
 
 	if (overlayFileName) {
 		if (strcmp(overlayFileName, "-")) {
@@ -210,6 +214,10 @@ static void writeROM() {
 		if (!overlayFile)
 			err("Failed to open overlay file \"%s\"", overlayFileName);
 	}
+	Defer closeOverlayFile{[&] {
+		if (overlayFile)
+			fclose(overlayFile);
+	}};
 
 	uint32_t nbOverlayBanks = checkOverlaySize();
 
@@ -230,11 +238,6 @@ static void writeROM() {
 			    sectionTypeInfo[SECTTYPE_ROMX].size
 			);
 	}
-
-	if (outputFile)
-		fclose(outputFile);
-	if (overlayFile)
-		fclose(overlayFile);
 }
 
 // Checks whether this character is legal as the first character of a symbol's name in a sym file
@@ -533,6 +536,7 @@ static void writeSym() {
 	}
 	if (!symFile)
 		err("Failed to open sym file \"%s\"", symFileName);
+	Defer closeSymFile{[&] { fclose(symFile); }};
 
 	fputs("; File generated by rgblink\n", symFile);
 
@@ -542,8 +546,6 @@ static void writeSym() {
 		for (uint32_t bank = 0; bank < sections[type].size(); bank++)
 			writeSymBank(sections[type][bank], type, bank);
 	}
-
-	fclose(symFile);
 }
 
 // Writes the map file, if applicable.
@@ -559,6 +561,7 @@ static void writeMap() {
 	}
 	if (!mapFile)
 		err("Failed to open map file \"%s\"", mapFileName);
+	Defer closeMapFile{[&] { fclose(mapFile); }};
 
 	writeMapSummary();
 
@@ -568,8 +571,6 @@ static void writeMap() {
 		for (uint32_t bank = 0; bank < sections[type].size(); bank++)
 			writeMapBank(sections[type][bank], type, bank);
 	}
-
-	fclose(mapFile);
 }
 
 void out_WriteFiles() {