Validate empty statements in switch statements

src/compiler/translator/ParseContext.cpp

@@ -2701,6 +2701,15 @@ void TParseContext::parseArrayInitDeclarator(const TPublicType &elementType,
     }
 }
 
+TIntermNode *TParseContext::addEmptyStatement(const TSourceLoc &location)
+{
+    // It's simpler to parse an empty statement as a constant expression rather than having a
+    // different type of node just for empty statements, that will be pruned from the AST anyway.
+    TIntermNode *node = CreateZeroNode(TType(EbtInt, EbpMedium));
+    node->setLine(location);
+    return node;
+}
+
 void TParseContext::setAtomicCounterBindingDefaultOffset(const TPublicType &publicType,
                                                          const TSourceLoc &location)
 {

src/compiler/translator/ParseContext.h

@@ -262,6 +262,8 @@ class TParseContext : angle::NonCopyable
                                   TIntermTyped *initializer,
                                   TIntermDeclaration *declarationOut);
 
+    TIntermNode *addEmptyStatement(const TSourceLoc &location);
+
     void parseDefaultPrecisionQualifier(const TPrecision precision,
                                         const TPublicType &type,
                                         const TSourceLoc &loc);

src/compiler/translator/glslang.y

@@ -1293,7 +1293,7 @@ statement_list
     ;
 
 expression_statement
-    : SEMICOLON  { $$ = 0; }
+    : SEMICOLON  { $$ = context->addEmptyStatement(@$); }
     | expression SEMICOLON  { $$ = $1; }
     ;
 

src/compiler/translator/glslang_tab.cpp

@@ -4591,7 +4591,7 @@ yyreduce:
 
   case 262:
 
-    { (yyval.interm.intermNode) = 0; }
+    { (yyval.interm.intermNode) = context->addEmptyStatement((yyloc)); }
 
     break;
 

src/tests/compiler_tests/ShaderValidation_test.cpp

@@ -5194,3 +5194,31 @@ TEST_F(FragmentShaderValidationTest, DuplicateFieldNamesInStructDeclaratorList)
         FAIL() << "Shader compilation succeeded, expecting failure:\n" << mInfoLog;
     }
 }
+
+// Test that an empty statement is not allowed in switch before the first case.
+TEST_F(FragmentShaderValidationTest, EmptyStatementInSwitchBeforeFirstCase)
+{
+    const std::string &shaderString =
+        R"(#version 300 es
+
+        precision mediump float;
+        uniform int u_zero;
+        out vec4 my_FragColor;
+
+        void main()
+        {
+            switch(u_zero)
+            {
+                    ;
+                case 0:
+                    my_FragColor = vec4(0.0);
+                default:
+                    my_FragColor = vec4(1.0);
+            }
+        })";
+
+    if (compile(shaderString))
+    {
+        FAIL() << "Shader compilation succeeded, expecting failure:\n" << mInfoLog;
+    }
+}