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[clang] Warn about deprecated volatile-qualified return types #137899

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Merged
merged 2 commits into from
May 10, 2025
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[clang] Warn about deprecated volatile-qualified return types #137899

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[clang] Warn about deprecated volatile-qualified return types
halbi2 Apr 29, 2025
d31a92d
Merge branch 'main' into depvol
cor3ntin May 10, 2025
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6 changes: 5 additions & 1 deletion clang/docs/ReleaseNotes.rst
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Expand Up @@ -509,6 +509,9 @@ Improvements to Clang's diagnostics
- Clang now prints the namespace for an attribute, if any,
when emitting an unknown attribute diagnostic.

- ``-Wvolatile`` now warns about volatile-qualified class return types
as well as volatile-qualified scalar return types. Fixes #GH133380

- Several compatibility diagnostics that were incorrectly being grouped under
``-Wpre-c++20-compat`` are now part of ``-Wc++20-compat``. (#GH138775)

Expand Down Expand Up @@ -921,7 +924,8 @@ Improvements
^^^^^^^^^^^^

Additional Information
======================

===================

A wide variety of additional information is available on the `Clang web
page <https://clang.llvm.org/>`_. The web page contains versions of the
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10 changes: 5 additions & 5 deletions clang/lib/Sema/SemaType.cpp
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Expand Up @@ -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;
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I see there is another place that issues warn_deprecated_volatile_return in Sema::CheckFunctionReturnType. I wonder why doesn't it suffice?

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I understand that CheckFunctionReturnType is used when checking the type of a function like using T = volatile int(); but this codepath here is used when checking a function declaration instead.

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ok, thanks for clarifying


// Objective-C ARC ownership qualifiers are ignored on the function
// return type (by type canonicalization). Complain if this attribute
// was written here.
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2 changes: 1 addition & 1 deletion clang/test/CXX/expr/expr.const/p2-0x.cpp
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Expand Up @@ -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}}
}
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7 changes: 7 additions & 0 deletions clang/test/SemaCXX/deprecated.cpp
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Expand Up @@ -231,6 +231,13 @@ namespace DeprecatedVolatile {
a = c = a;
b += a;
}

volatile struct amber jurassic();
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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?

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Lines 207-215 are that, are they not?

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Yeah, these are what I meant. Thanks!

// 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@-2 {{volatile-qualified parameter type 'volatile struct amber' is deprecated}}
void fly(volatile struct pterosaur* pteranodon);
}

namespace ArithConv {
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