From d3a0761d038e2f01dfdaf89f8c6029c8c965da64 Mon Sep 17 00:00:00 2001
From: Andrew Price <andy@adpx.net>
Date: Thu, 6 Nov 2025 05:01:19 +0000
Subject: [PATCH] Fix consume_line_continuations() skipping characters

This function increments the code index by 2 when a line continuation is
found, additional to the loop increment, so it skips over the next
character following a line continuation.

In shader code like

   #define FUN_FUN(n)\
   void fun1() { return;\
   }\
   void fun2() { return; }
   FUN_FUN(1.0)

the first } will visibly get skipped, causing an error. The 'v' in
'void' will also get missed, but as the next 'o' is enough to decide to
end the loop, that is less obvious.

Simplify consume_line_continuations() to remove the unnecessary offset
parameter and the extra loop index variable, and increment index the
right amount.
---
 servers/rendering/shader_preprocessor.cpp | 37 +++++++++++------------
 servers/rendering/shader_preprocessor.h   |  2 +-
 2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/servers/rendering/shader_preprocessor.cpp b/servers/rendering/shader_preprocessor.cpp
index ee34504b79b8..9876ca0fc262 100644
--- a/servers/rendering/shader_preprocessor.cpp
+++ b/servers/rendering/shader_preprocessor.cpp
@@ -78,24 +78,23 @@ char32_t ShaderPreprocessor::Tokenizer::peek() {
 	return 0;
 }
 
-int ShaderPreprocessor::Tokenizer::consume_line_continuations(int p_offset) {
+int ShaderPreprocessor::Tokenizer::consume_line_continuations() {
 	int skips = 0;
 
-	for (int i = index + p_offset; i < size; i++) {
-		char32_t c = code[i];
-		if (c == '\\') {
-			if (i + 1 < size && code[i + 1] == '\n') {
-				// This line ends with "\" and "\n" continuation.
-				add_generated(Token('\n', line));
-				line++;
-				skips++;
-
-				i = i + 2;
-				index = i;
-			} else {
-				break;
+	for (; index < size; index++) {
+		char32_t c = code[index];
+		if (c != '\\') {
+			if (is_whitespace(c)) {
+				continue;
 			}
-		} else if (!is_whitespace(c)) {
+			break;
+		}
+		if (index + 1 < size && code[index + 1] == '\n') {
+			add_generated(Token('\n', line));
+			line++;
+			skips++;
+			index++;
+		} else {
 			break;
 		}
 	}
@@ -106,11 +105,11 @@ LocalVector<ShaderPreprocessor::Token> ShaderPreprocessor::Tokenizer::advance(ch
 	LocalVector<ShaderPreprocessor::Token> tokens;
 
 	while (index < size) {
-		char32_t c = code[index++];
-		if (c == '\\' && consume_line_continuations(-1) > 0) {
+		char32_t c = code[index];
+		if (c == '\\' && consume_line_continuations() > 0) {
 			continue;
 		}
-
+		index++;
 		if (c == '\n') {
 			add_generated(ShaderPreprocessor::Token('\n', line));
 			line++;
@@ -145,7 +144,7 @@ String ShaderPreprocessor::Tokenizer::get_identifier(bool *r_is_cursor, bool p_s
 
 	while (true) {
 		char32_t c = peek();
-		if (c == '\\' && consume_line_continuations(0) > 0) {
+		if (c == '\\' && consume_line_continuations() > 0) {
 			continue;
 		}
 
diff --git a/servers/rendering/shader_preprocessor.h b/servers/rendering/shader_preprocessor.h
index 3b386af68797..2e41f882a9c1 100644
--- a/servers/rendering/shader_preprocessor.h
+++ b/servers/rendering/shader_preprocessor.h
@@ -89,7 +89,7 @@ class ShaderPreprocessor {
 		int get_line() const;
 		int get_index() const;
 		char32_t peek();
-		int consume_line_continuations(int p_offset);
+		int consume_line_continuations();
 
 		void get_and_clear_generated(LocalVector<char32_t> *r_out);
 		void backtrack(char32_t p_what);