Fix #14896: false positive: missing co_return in void function (#8719)

Author: ludviggunne

lib/checkfunctions.cpp

@@ -329,6 +329,8 @@ void CheckFunctionsImpl::checkMissingReturn()
             continue;
         if (Function::returnsVoid(function, true))
             continue;
+        if (Function::isCoroutine(function, mSettings.standards, *mTokenizer))
+            continue;
         const Token *errorToken = checkMissingReturnScope(scope->bodyEnd, mSettings.library);
         if (errorToken)
             missingReturnError(errorToken);

lib/symboldatabase.cpp

@@ -3407,6 +3407,20 @@ bool Function::returnsVoid(const Function* function, bool unknown)
     });
 }
 
+bool Function::isCoroutine(const Function* function, const Standards &standards, const Tokenizer &tokens)
+{
+    if (!tokens.isCPP() || standards.cpp < Standards::CPP20)
+        return false;
+    if (!function->functionScope)
+        return false;
+    const Scope *scope = function->functionScope;
+    for (const Token *tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
+        if (Token::Match(tok, "co_return|co_await|co_yield"))
+            return true;
+    }
+    return false;
+}
+
 std::vector<const Token*> Function::findReturns(const Function* f)
 {
     std::vector<const Token*> result;

lib/symboldatabase.h

@@ -945,6 +945,7 @@ class CPPCHECKLIB Function {
     static bool returnsStandardType(const Function* function, bool unknown = false);
 
     static bool returnsVoid(const Function* function, bool unknown = false);
+    static bool isCoroutine(const Function* function, const Standards &standards, const Tokenizer &tokens);
 
     static std::vector<const Token*> findReturns(const Function* f);
 

test/testfunctions.cpp

@@ -86,6 +86,7 @@ class TestFunctions : public TestFixture {
         TEST_CASE(checkMissingReturn5);
         TEST_CASE(checkMissingReturn6); // #13180
         TEST_CASE(checkMissingReturn7); // #14370 - FN try/catch
+        TEST_CASE(checkMissingReturn8);
         TEST_CASE(checkMissingReturnStdInt); // #14482 - FN std::int32_t
 
         // std::move for locar variable
@@ -1927,6 +1928,14 @@ class TestFunctions : public TestFixture {
         ASSERT_EQUALS("[test.cpp:3:19]: (error) Found an exit path from function with non-void return type that has missing return statement [missingReturn]\n", errout_str());
     }
 
+    void checkMissingReturn8() {
+        const Settings s = settingsBuilder(settings).cpp(Standards::CPP20).build();
+        check("boost::asio::awaitable<void> test() {\n"
+              "        co_return;\n"
+              "}\n",s);
+        ASSERT_EQUALS("", errout_str());
+    }
+
     void checkMissingReturnStdInt() {// #14482 - FN
         check("std::int32_t f() {}\n");
         ASSERT_EQUALS("[test.cpp:1:19]: (error) Found an exit path from function with non-void return type that has missing return statement [missingReturn]\n", errout_str());