Reduce more nesting depth, and fix an error message

src/gfx/process.cpp

@@ -880,7 +880,11 @@ static void outputUnoptimizedTileData(
 
 	for (auto [tile, attr] : zip(png.visitAsTiles(), attrmap)) {
 		// Do not emit fully-background tiles.
-		if (!attr.isBackgroundTile()) {
+		if (attr.isBackgroundTile()) {
+			++tileIdx;
+			continue;
+		}
+
 		// If the tile is fully transparent, this defaults to palette 0.
 		Palette const &palette = palettes[attr.getPalID(mappings)];
 
@@ -900,12 +904,10 @@ static void outputUnoptimizedTileData(
 
 		if (!empty && tileIdx >= nbKeptTiles) {
 			warning(
-				    WARNING_TRIM_NONEMPTY,
-				    "Trimming a nonempty tile (configure with '-x/--trim-end'"
+			    WARNING_TRIM_NONEMPTY, "Trimming a nonempty tile (configure with '-x/--trim-end')"
 			);
 			break; // Don't repeat the warning for subsequent tiles
 		}
-		}
 		++tileIdx;
 	}
 	assume(nbKeptTiles <= tileIdx && tileIdx <= nbTiles);

src/link/output.cpp

@@ -263,17 +263,16 @@ static void writeROM() {
 
 static void writeSymName(std::string const &name, FILE *file) {
 	for (char const *ptr = name.c_str(); *ptr != '\0';) {
-		char c = *ptr;
-
-		if (continuesIdentifier(c)) {
 		// Output legal ASCII characters as-is
+		if (char c = *ptr; continuesIdentifier(c)) {
 			putc(c, file);
 			++ptr;
-		} else {
+			continue;
+		}
+
 		// Output illegal characters using Unicode escapes ('\u' or '\U')
 		// Decode the UTF-8 codepoint; or at least attempt to
 		uint32_t state = UTF8_ACCEPT, codepoint;
-
 		do {
 			decode(&state, &codepoint, *ptr);
 			if (state == UTF8_REJECT) {
@@ -288,10 +287,8 @@ static void writeSymName(std::string const &name, FILE *file) {
 			}
 			++ptr;
 		} while (state != UTF8_ACCEPT);
-
 		fprintf(file, codepoint <= 0xFFFF ? "\\u%04" PRIx32 : "\\U%08" PRIx32, codepoint);
 	}
-	}
 }
 
 // Comparator function for `std::stable_sort` to sort symbols

test/gfx/warn_trim_nonempty.err

@@ -1,2 +1,2 @@
 warning: [-Wtrim-nonempty]
-    Trimming a nonempty tile (configure with '-x/--trim-end'
+    Trimming a nonempty tile (configure with '-x/--trim-end')