https://github.com/snarang181 updated
https://github.com/llvm/llvm-project/pull/145166
>From 004e79ee8cccc56a965459ce0372de97f4a89d0c Mon Sep 17 00:00:00 2001
From: Samarth Narang <snar...@umass.edu>
Date: Sat, 21 Jun 2025 08:42:00 -0400
Subject: [PATCH] Suppress noreturn warning if last statement in a function is
a throw
---
clang/lib/Sema/AnalysisBasedWarnings.cpp | 45 ++++++++++++++++++++
clang/test/SemaCXX/wreturn-always-throws.cpp | 19 +++++++++
2 files changed, 64 insertions(+)
create mode 100644 clang/test/SemaCXX/wreturn-always-throws.cpp
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp
b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 2a107a36e24b4..85a5d99c710d5 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -626,6 +626,31 @@ struct CheckFallThroughDiagnostics {
} // anonymous namespace
+static bool isKnownToAlwaysThrow(const FunctionDecl *FD) {
+ if (!FD->hasBody())
+ return false;
+ const Stmt *Body = FD->getBody();
+ const Stmt *OnlyStmt = nullptr;
+
+ if (const auto *Compound = dyn_cast<CompoundStmt>(Body)) {
+ if (Compound->size() != 1)
+ return false; // More than one statement, can't be known to always throw.
+ OnlyStmt = *Compound->body_begin();
+ } else {
+ OnlyStmt = Body;
+ }
+
+ // Unwrap ExprWithCleanups if necessary.
+ if (const auto *EWC = dyn_cast<ExprWithCleanups>(OnlyStmt)) {
+ OnlyStmt = EWC->getSubExpr();
+ }
+ // Check if the only statement is a throw expression.
+ if (isa<CXXThrowExpr>(OnlyStmt)) {
+ return true; // Known to always throw.
+ }
+ return false; // Not known to always throw.
+}
+
/// CheckFallThroughForBody - Check that we don't fall off the end of a
/// function that should return a value. Check that we don't fall off the end
/// of a noreturn function. We assume that functions and blocks not marked
@@ -681,6 +706,26 @@ static void CheckFallThroughForBody(Sema &S, const Decl
*D, const Stmt *Body,
if (CD.diag_FallThrough_HasNoReturn)
S.Diag(RBrace, CD.diag_FallThrough_HasNoReturn) << CD.FunKind;
} else if (!ReturnsVoid && CD.diag_FallThrough_ReturnsNonVoid) {
+ // If the final statement is a call to an always-throwing function,
+ // don't warn about the fall-through.
+ if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+ if (const auto *CS = dyn_cast<CompoundStmt>(Body)) {
+ if (!CS->body_empty()) {
+ const Stmt *LastStmt = CS->body_back();
+ // Unwrap ExprWithCleanups if necessary.
+ if (const auto *EWC = dyn_cast<ExprWithCleanups>(LastStmt)) {
+ LastStmt = EWC->getSubExpr();
+ }
+ if (const auto *CE = dyn_cast<CallExpr>(LastStmt)) {
+ if (const FunctionDecl *Callee = CE->getDirectCallee()) {
+ if (isKnownToAlwaysThrow(Callee)) {
+ return; // Don't warn about fall-through.
+ }
+ }
+ }
+ }
+ }
+ }
bool NotInAllControlPaths = FallThroughType == MaybeFallThrough;
S.Diag(RBrace, CD.diag_FallThrough_ReturnsNonVoid)
<< CD.FunKind << NotInAllControlPaths;
diff --git a/clang/test/SemaCXX/wreturn-always-throws.cpp
b/clang/test/SemaCXX/wreturn-always-throws.cpp
new file mode 100644
index 0000000000000..73f2f1085605a
--- /dev/null
+++ b/clang/test/SemaCXX/wreturn-always-throws.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fsyntax-only -Wreturn-type -verify %s
+// expected-no-diagnostics
+
+namespace std {
+ class runtime_error {
+ public:
+ runtime_error(const char *);
+ };
+ class string {};
+}
+
+void throwError(const string& msg) {
+ throw std::runtime_error(msg);
+}
+
+int ensureZero(const int i) {
+ if (i == 0) return 0;
+ throwError("ERROR"); // no-warning
+}
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