[Fix] (ShaderTranspiler): stop blanking block comments in the source handed to glslang

- BlankBlockComments replaced comment chars with spaces but preserved interior newlines, so a block comment spanning a newline inside a #define truncated the macro body (VALUE became empty)
- glslang has a conformant preprocessor and collapses a block comment to one space across newlines, so the delivered source now keeps comments intact and lets glslang handle them
- Fixes KHR-GL3x.shaders.preprocessor multiline_comment_define / redefine_object_multiline_comment / function_redefinition_3 (6 cases, both devices)
- FilterUnsupportedGpuShaderInt64 relied on the blanking to skip commented-out #extension lines; it now masks comments locally (MaskCommentsAndQuotedText) like the sibling passes, collecting edits and applying them back-to-front
- conditional_inclusion.basic_2 (defined() via macro expansion) stays failing by design: glslang rejects it as UB and working around it would mean re-running preprocessing MobileGL defers to glslang

MobileGL/MG_Test/Program/ProgramUtilTest.cpp

@@ -238,6 +238,77 @@ void main() {
     }
 }
 
+// KHR-GL33.shaders.preprocessor.* — a block comment is one preprocessing token that the C/GLSL
+// preprocessor replaces with a single space, even when it spans newlines inside a directive. glslang
+// handles this natively, so MobileGL must not mangle it. These reproduce the CTS cases that failed
+// because comment blanking preserved the interior newline, truncating multi-line #define bodies.
+static void ExpectCompiles(MobileGL::ShaderStage stage, GLenum glStage, MobileGL::String source) {
+    using namespace MG_Util::ShaderTranspiler;
+    PreprocessShaderSource(stage, source);
+    ShaderAttrib attrib{.shaderType = glStage, .sourceStr = source};
+    auto res = ShaderCompiler::CompileShader(attrib);
+    if (!res) {
+        FAIL() << "errc: " << res.error().errc << "\nlog: " << res.error().log << "\nsource:\n" << source;
+    }
+}
+
+TEST_F(ProgramUtilTest, PreprocessMultilineCommentInDefineBodyCompiles) {
+    ExpectCompiles(ShaderStage::Fragment, GL_FRAGMENT_SHADER,
+                   R"(#version 330
+precision mediump float;
+out float out0;
+#define VALUE /* current
+            value */ 4.2
+
+void main()
+{
+    out0 = VALUE;
+})");
+}
+
+TEST_F(ProgramUtilTest, PreprocessRedefineObjectMultilineCommentCompiles) {
+    ExpectCompiles(ShaderStage::Fragment, GL_FRAGMENT_SHADER,
+                   R"(#version 330
+precision mediump float;
+out float out0;
+#    define  VAL1 1.0
+#define        VAL2 2.0
+
+#define RES2 /* fdsjklfdsjkl
+                dsfjkhfdsjkh
+                fdsjklhfdsjkh */ (RES1 * VAL2)
+#define RES1    (VAL2 / VAL1)
+#define RES2    /* ewrlkjhsadf */ (RES1 * VAL2)
+#define VALUE    (RES2 + RES1)
+
+void main()
+{
+    out0 = VALUE;
+})");
+}
+
+TEST_F(ProgramUtilTest, PreprocessFunctionMacroRedefinitionMultilineCommentCompiles) {
+    ExpectCompiles(ShaderStage::Fragment, GL_FRAGMENT_SHADER,
+                   R"(#version 330
+precision mediump float;
+out float out0;
+# define FUNC(a,b)        (a  +b)
+# define FUNC(a,b)(a    /* comment
+                         */ +b)
+
+void main()
+{
+    out0 = FUNC(1.0, 2.0);
+})");
+}
+
+// Note: KHR-GL3x.shaders.preprocessor.conditional_inclusion.basic_2 (`#define AAA defined(BBB)` used
+// in `#if !AAA`) is intentionally NOT handled here. Generating the `defined` operator via macro
+// expansion is undefined per the C/GLSL preprocessor spec, and glslang deliberately rejects it
+// ("'defined' : cannot use in preprocessor expression when expanded from macros"). Making it pass
+// would require MobileGL to run its own macro expansion ahead of glslang, which is exactly the
+// preprocessing we defer to glslang; the two cases stay failing by design.
+
 TEST_F(ProgramUtilTest, PreprocessLegacyFragmentShaderModernizesGlmarkStyleSource) {
     using namespace MG_Util::ShaderTranspiler;
 

MobileGL/MG_Util/ShaderTranspiler/ShaderSourceProcessor.cpp

@@ -956,15 +956,28 @@ namespace {
             return;
         }
 
+        // Detect the directive on a comment/string-masked copy so a commented-out
+        // "#extension GL_ARB_gpu_shader_int64" is never turned into a synthesized #error. Comments are
+        // no longer blanked in the delivered source (glslang handles them), so this pass must mask
+        // locally like its siblings. Masking preserves offsets, so edits collected against the scan
+        // apply verbatim to `source`; they are applied back-to-front to keep earlier offsets valid.
+        const MobileGL::String scan = MaskCommentsAndQuotedText(source);
+        struct DirectiveEdit {
+            SizeT pos;
+            SizeT len;
+            MobileGL::String replacement;
+        };
+        Vector<DirectiveEdit> edits;
+
         SizeT lineStart = 0;
-        while (lineStart < source.size()) {
+        while (lineStart < scan.size()) {
-            SizeT lineEnd = source.find('\n', lineStart);
+            SizeT lineEnd = scan.find('\n', lineStart);
             const bool hasLineBreak = lineEnd != MobileGL::String::npos;
             if (!hasLineBreak) {
-                lineEnd = source.size();
+                lineEnd = scan.size();
             }
 
-            const MobileGL::String line = source.substr(lineStart, lineEnd - lineStart);
+            const MobileGL::String line = scan.substr(lineStart, lineEnd - lineStart);
             SizeT probe = 0;
             while (probe < line.size() && std::isspace(static_cast<unsigned char>(line[probe]))) {
                 probe++;
@@ -1006,16 +1019,12 @@ namespace {
                             const MobileGL::String behavior = TrimDirectiveToken(line.substr(probe));
                             const SizeT replaceLen = lineEnd - lineStart + (hasLineBreak ? 1 : 0);
                             if (behavior == "require") {
-                                const MobileGL::String replacement =
+                                edits.push_back({lineStart, replaceLen,
-                                    "#error GL_ARB_gpu_shader_int64 is not advertised by MobileGL\n";
+                                                 "#error GL_ARB_gpu_shader_int64 is not advertised by MobileGL\n"});
-                                source.replace(lineStart, replaceLen, replacement);
-                                lineStart += replacement.size();
                             } else if (behavior == "enable" || behavior == "warn") {
-                                source.replace(lineStart, replaceLen, "\n");
+                                edits.push_back({lineStart, replaceLen, "\n"});
-                                lineStart++;
-                            } else {
-                                lineStart = lineEnd + (hasLineBreak ? 1 : 0);
                             }
+                            lineStart = lineEnd + (hasLineBreak ? 1 : 0);
                             continue;
                         }
                     }
@@ -1025,6 +1034,10 @@ namespace {
             lineStart = lineEnd + (hasLineBreak ? 1 : 0);
         }
 
+        for (auto it = edits.rbegin(); it != edits.rend(); ++it) {
+            source.replace(it->pos, it->len, it->replacement);
+        }
+
         ReplaceIdentifier(source, "GL_ARB_gpu_shader_int64", "MG_DISABLED_GL_ARB_gpu_shader_int64");
     }
 
@@ -1247,8 +1260,13 @@ namespace MobileGL {
                 const ShaderLanguageInfo originalLanguage = InspectShaderLanguage(source);
                 NormalizeVersionDirective(source, originalLanguage);
 
-                BlankBlockComments(source);
+                // Comments are left intact for glslang's own preprocessor: a block comment is a single
-
+                // preprocessing token that collapses to one space even across newlines and inside a
+                // directive, so blanking it here (which preserved the interior newlines) truncated
+                // multi-line #define bodies and broke otherwise-valid shaders (KHR-GL3x.shaders.
+                // preprocessor multiline_comment_define / redefine_object / function_redefinition).
+                // Every MobileGL pass that must ignore comment/string text already masks them locally
+                // via MaskCommentsAndQuotedText/TokenizeCode, so the source we hand glslang keeps them.
                 NormalizeLineDirectives(source);
 
                 // noperspective is intentionally NOT touched here. It is core in desktop GLSL (1.30+)