Fix GLSL global const diagnostic regression

source/slang/slang-check-decl.cpp

@@ -240,13 +240,19 @@ struct SemanticsDeclModifiersVisitor : public SemanticsDeclVisitorBase,
         // In HLSL, const global variables without static are uniform parameters
         // that cannot have default values
         // Exception: specialization constants are allowed to have initializers
+        // Exception: In GLSL mode, global const variables are real constants, not uniform
+        // parameters
         if (isGlobalDecl(decl) && (hasConst || hasUniform) && !hasStatic &&
             !hasSpecializationConstant && decl->initExpr)
         {
-            getSink()->diagnose(
-                decl,
-                Diagnostics::constGlobalVarWithInitRequiresStatic,
-                decl->getName());
+            auto moduleDecl = getModuleDecl(decl);
+            if (!moduleDecl || !moduleDecl->hasModifier<GLSLModuleModifier>())
+            {
+                getSink()->diagnose(
+                    decl,
+                    Diagnostics::constGlobalVarWithInitRequiresStatic,
+                    decl->getName());
+            }
         }
     }
 

tests/diagnostics/glsl-global-const-with-init.slang

@@ -0,0 +1,26 @@
+//TEST:SIMPLE(filecheck=CHK): -target glsl -stage fragment -entry main -allow-glsl
+
+// Test for GLSL mode: global const variables with initializers should be allowed
+// In GLSL mode, global const variables are real constants, not uniform parameters
+// This should NOT produce the error 31224 that would trigger in HLSL mode
+
+#version 450
+
+// These should NOT trigger error 31224 in GLSL mode (they would in HLSL)
+const float globalConstWithInit = 1.0;        // OK in GLSL - real constant
+const vec3 globalVecConst = vec3(1.0, 2.0, 3.0); // OK in GLSL - real constant
+const int globalIntConst = 42;                // OK in GLSL - real constant
+
+// Regular uniforms without const should still be allowed
+uniform float uniformFloat;                   // OK - uniform without const
+uniform vec4 uniformVec;                     // OK - uniform without const
+
+// CHK-NOT: error 31224
+// CHK: void main()
+
+out vec4 fragColor;
+
+void main() 
+{
+    fragColor = vec4(globalConstWithInit, globalVecConst.x, globalIntConst, 1.0);
+}

tests/diagnostics/hlsl-global-const-with-init-still-errors.slang

@@ -0,0 +1,18 @@
+//TEST:SIMPLE(filecheck=CHK): -target hlsl -entry main
+
+// Test to ensure HLSL mode still produces the diagnostic for global const with initializers
+// This verifies our fix doesn't break existing HLSL behavior
+
+// This should trigger error 31224 in HLSL mode
+//CHK: ([[# @LINE + 1]]): error 31224: global const variable with initializer must be declared static: 'globalConstWithInit'
+const float globalConstWithInit = 1.0f;
+
+// This should also trigger error 31224 in HLSL mode  
+//CHK: ([[# @LINE + 1]]): error 31224: global const variable with initializer must be declared static: 'uniformWithInit'
+uniform float uniformWithInit = 2.0f;
+
+[shader("vertex")]
+float4 main() : SV_Position
+{
+    return float4(1, 0, 0, 1);
+}