[clang][Parser] Fix crash on malformed using declaration in constexpr function

[el-ev]

• Closes Clang frontend crashes on invalid usage of [[deprecated]] inside constexpr function #144264

[llvmbot]

@llvm/pr-subscribers-clang

Author: Iris Shi (el-ev)

Changes

• Closes #144264

---

Full diff: https://github.com/llvm/llvm-project/pull/144286.diff

2 Files Affected:

• (modified) clang/lib/Parse/ParseDeclCXX.cpp (+4)
• (added) clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp (+8)

diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index f31c9265a0074..ed401c894f71c 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -760,6 +760,10 @@ Parser::DeclGroupPtrTy Parser::ParseUsingDeclaration(
 
     Decl *AD = ParseAliasDeclarationAfterDeclarator(
         TemplateInfo, UsingLoc, D, DeclEnd, AS, Attrs, &DeclFromDeclSpec);
+
+    if (!AD)
+      return nullptr;
+    
     return Actions.ConvertDeclToDeclGroup(AD, DeclFromDeclSpec);
   }
 
diff --git a/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp b/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp
new file mode 100644
index 0000000000000..82104779ca67e
--- /dev/null
+++ b/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// issue144264
+constexpr void test() 
+{ 
+    using TT = struct T[deprecated{}; 
+    // expected-error@-1 {{use of undeclared identifier 'deprecated'}}
+}

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[zwuis]

Please add a release note.

[el-ev]

Added.

[AaronBallman]

It looks like the test coverage was dropped in a recent commit.

[AaronBallman]

LGTM!

[shafik]

Next time please add more details in the summary, this is key for reviewers so that they can digest the PR without leaving for more context. Even in very simple PRs it is good to do.

For this one something along the lines of Parser::ParseUsingDeclaration was not that the result of ParseAliasDeclarationAfterDeclarator was not a nullptr. The fix is to check the result and return nullptr

[el-ev]

Next time please add more details in the summary, this is key for reviewers so that they can digest the PR without leaving for more context. Even in very simple PRs it is good to do.

For this one something along the lines of Parser::ParseUsingDeclaration was not that the result of ParseAliasDeclarationAfterDeclarator was not a nullptr. The fix is to check the result and return nullptr

Thank you for your kind suggestions.