[clang] [HLSL] Allow EmptyDecl in cbuffer/tbuffer (PR #128250)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-hlsl

Author: Chris B (llvm-beanz)

<details>
<summary>Changes</summary>

We do handle EmptyDecls in codegen already as of #<!-- -->124886, but we were blocking them in Sema. EmptyDecls tend to be caused by extra semicolons which are not illegal.

Fixes #<!-- -->128238

---
Full diff: https://github.com/llvm/llvm-project/pull/128250.diff


2 Files Affected:

- (modified) clang/lib/Parse/ParseHLSL.cpp (+1-1) 
- (modified) clang/test/SemaHLSL/cb_error.hlsl (+12) 


``````````diff
diff --git a/clang/lib/Parse/ParseHLSL.cpp b/clang/lib/Parse/ParseHLSL.cpp
index 443bf2b9ec626..612e1ab0084ff 100644
--- a/clang/lib/Parse/ParseHLSL.cpp
+++ b/clang/lib/Parse/ParseHLSL.cpp
@@ -30,7 +30,7 @@ static bool validateDeclsInsideHLSLBuffer(Parser::DeclGroupPtrTy DG,
   // Only allow function, variable, record decls inside HLSLBuffer.
   for (DeclGroupRef::iterator I = Decls.begin(), E = Decls.end(); I != E; ++I) {
     Decl *D = *I;
-    if (isa<CXXRecordDecl, RecordDecl, FunctionDecl, VarDecl>(D))
+    if (isa<CXXRecordDecl, RecordDecl, FunctionDecl, VarDecl, EmptyDecl>(D))
       continue;
 
     // FIXME: support nested HLSLBuffer and namespace inside HLSLBuffer.
diff --git a/clang/test/SemaHLSL/cb_error.hlsl b/clang/test/SemaHLSL/cb_error.hlsl
index 133adeeb2068b..95c917a9bb9ee 100644
--- a/clang/test/SemaHLSL/cb_error.hlsl
+++ b/clang/test/SemaHLSL/cb_error.hlsl
@@ -47,3 +47,15 @@ tbuffer B {
   // expected-error at +1 {{unknown type name 'flaot'}}
   flaot f;
 }
+
+// None of these should produce an error!
+cbuffer EmptyCBuffer {}
+
+cbuffer EmptyDeclCBuffer {
+  ;
+}
+
+cbuffer EmptyDecl2CBuffer {
+  ;
+  int X;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/128250