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[clang] [Sema] Suggest [[noreturn]] for void functions that always throw #146234

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Merged
merged 4 commits into from
Jun 30, 2025
Merged

[clang] [Sema] Suggest [[noreturn]] for void functions that always throw #146234

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588ae1c
Emit a suggestion to explicitly mark the function with [[noreturn]] i…
snarang181 Jun 28, 2025
8a0e8f8
Remove condition for emitting noreturn suggestion
snarang181 Jun 29, 2025
ee29ba2
Merge remote-tracking branch 'origin/main' into clang-emit-noreturn-s…
snarang181 Jun 29, 2025
3f02a48
Add inline comment to clarify the purpose of the argument
Jun 30, 2025
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3 changes: 3 additions & 0 deletions clang/lib/Sema/SemaDeclAttr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1979,6 +1979,9 @@ void clang::inferNoReturnAttr(Sema &S, const Decl *D) {
if (!FD->hasAttr<NoReturnAttr>() && !FD->hasAttr<InferredNoReturnAttr>() &&
isKnownToAlwaysThrow(FD)) {
NonConstFD->addAttr(InferredNoReturnAttr::CreateImplicit(S.Context));

// Emit a diagnostic suggesting the function being marked [[noreturn]].
S.Diag(FD->getLocation(), diag::warn_suggest_noreturn_function) << 0 << FD;
}
}

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23 changes: 23 additions & 0 deletions clang/test/SemaCXX/wmissing-noreturn-suggestion.cpp
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@@ -0,0 +1,23 @@
// RUN: %clang_cc1 -fsyntax-only -fcxx-exceptions -fexceptions -Wreturn-type -Wmissing-noreturn -verify %s

namespace std {
class string {
public:
string(const char*);
};
class runtime_error {
public:
runtime_error(const string&);
};
}

// This function always throws. Suggest [[noreturn]].
void throwError(const std::string& msg) { // expected-warning {{function 'throwError' could be declared with attribute 'noreturn'}}
throw std::runtime_error(msg);
}

// The non-void caller should not warn about missing return.
int ensureZero(int i) {
if (i == 0) return 0;
throwError("ERROR"); // no-warning
}