[clang] Warn about deprecated volatile-qualified return types

[halbi2]

Fixes #133380

[llvmbot]

@llvm/pr-subscribers-clang

Author: None (halbi2)

Changes

Fixes #133380

---

Full diff: https://github.com/llvm/llvm-project/pull/137899.diff

3 Files Affected:

• (modified) clang/lib/Sema/SemaType.cpp (+5-5)
• (modified) clang/test/CXX/expr/expr.const/p2-0x.cpp (+1-1)
• (modified) clang/test/SemaCXX/deprecated.cpp (+7)

diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 6e7ee8b5506ff..31bdc97d014d6 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -5056,13 +5056,13 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
           S.Diag(DeclType.Loc, diag::err_func_returning_qualified_void) << T;
         } else
           diagnoseRedundantReturnTypeQualifiers(S, T, D, chunkIndex);
-
-        // C++2a [dcl.fct]p12:
-        //   A volatile-qualified return type is deprecated
-        if (T.isVolatileQualified() && S.getLangOpts().CPlusPlus20)
-          S.Diag(DeclType.Loc, diag::warn_deprecated_volatile_return) << T;
       }
 
+      // C++2a [dcl.fct]p12:
+      //   A volatile-qualified return type is deprecated
+      if (T.isVolatileQualified() && S.getLangOpts().CPlusPlus20)
+        S.Diag(DeclType.Loc, diag::warn_deprecated_volatile_return) << T;
+
       // Objective-C ARC ownership qualifiers are ignored on the function
       // return type (by type canonicalization). Complain if this attribute
       // was written here.
diff --git a/clang/test/CXX/expr/expr.const/p2-0x.cpp b/clang/test/CXX/expr/expr.const/p2-0x.cpp
index df5ce108aca82..c6c3381be5523 100644
--- a/clang/test/CXX/expr/expr.const/p2-0x.cpp
+++ b/clang/test/CXX/expr/expr.const/p2-0x.cpp
@@ -356,7 +356,7 @@ namespace LValueToRValue {
   // - a non-volatile glvalue of literal type that refers to a non-volatile
   //   temporary object whose lifetime has not ended, initialized with a
   //   constant expression;
-  constexpr volatile S f() { return S(); }
+  constexpr volatile S f() { return S(); } // cxx20-warning {{volatile-qualified return type 'volatile S' is deprecated}}
   static_assert(f().i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
   static_assert(((volatile const S&&)(S)0).i, ""); // expected-error {{constant expression}} expected-note {{read of volatile-qualified type}}
 }
diff --git a/clang/test/SemaCXX/deprecated.cpp b/clang/test/SemaCXX/deprecated.cpp
index a24b40d8e622a..061fa8b54dff1 100644
--- a/clang/test/SemaCXX/deprecated.cpp
+++ b/clang/test/SemaCXX/deprecated.cpp
@@ -231,6 +231,13 @@ namespace DeprecatedVolatile {
     a = c = a;
     b += a;
   }
+
+  volatile struct amber jurassic();
+    // cxx20-warning@-1 {{volatile-qualified return type 'volatile struct amber' is deprecated}}
+  void trex(volatile short left_arm, volatile struct amber right_arm);
+    // cxx20-warning@-1 {{volatile-qualified parameter type 'volatile short' is deprecated}}
+    // cxx20-warning@-1 {{volatile-qualified parameter type 'volatile struct amber' is deprecated}}
+  void fly(volatile struct pterosaur* pteranodon);
 }
 
 namespace ArithConv {

[Fznamznon]

Thank you for the fix, could you please also add a release note?

[Fznamznon]

I see there is another place that issues warn_deprecated_volatile_return in Sema::CheckFunctionReturnType. I wonder why doesn't it suffice?

[Fznamznon]

As I can see, if the return type is not a struct/class, the warning is issued. Could you please add a test case with volatile qualifier applied to a basic type (for example int) and make sure there is no double diagnostic issued now?

[shafik]

Can you add more details in the summary. Specifically your approach to fixing the issue.

Something along the lines of "In GetFullTypeForDeclarator ... moved check ... b/c ..."