False positive Using object that is a temporary. [danglingTemporaryLifetime] or what am I missing ?

[Rob Deckers]

I think we have a false positive, but I am not 100% sure.
We are compiling for C++20

CppCheck notification

Cppcheck 2.13.0
error: Using object that is a temporary. [danglingTemporaryLifetime]
    auto er_result = er({expected});
                         ^
note: Return object.
    return {.strMsg = message.c_str()
           ^
note: Passed to reference.
ErrorInterface::ErrorResponseElement elem(const std::string& message,
                                                                                        ^
note: Pointer to container is created here.
            .strMsg = message.c_str(),
                                   ^
note: Passed to reference.
ErrorInterface::ErrorResponseElement elem(const std::string& message,
                                                                                        ^
note: Passed to constructor of 'ErrorResponseElement'.
            .strMsg = message.c_str(),
                    ^
note: Passed to 'elem'.
    const auto expected = elem("Metallica");
                                  ^
note: Temporary created here.
    const auto expected = elem("Metallica");
                                  ^
note: Using object that is a temporary.
    auto er_result = er({expected});

This is a simplification of the code, but I hope it provides enough context.

struct ErrorResponseElement {
    StaticString<55> strMsg;
};

/** Vector of response elements. */
using ErrorResponseElements = std::vector<ErrorResponseElement>;

/** Factory function top create a TestErrorResponse. */
TestErrorResponse er(ErrorResponseElements elements)
{
    return TestErrorResponse{std::move(elements)};
}

/** Factory function to create an ErrorResponseElement. */
ErrorInterface::ErrorResponseElement elem(const std::string& message)
{
    return {.strMsg = message.c_str()};
}

TEST_F(DiagnosticsAdapterTest, ReportScoped)
{
    const auto expected = elem("Metallica");
    auto er_result = er({expected});
}

[Daniel Marjamäki]

hmm I fail to reproduce. I copied your example code to fp1.cpp and used this command:

$ ../.cppcheck/cppcheck-2.13.0 --enable=all --library=googletest fp1.cpp
Checking fp1.cpp ...
fp1.cpp:20:0: style: The function '__DiagnosticsAdapterTest_ReportScoped' is never used. [unusedFunction]
TEST_F(DiagnosticsAdapterTest, ReportScoped)
^
nofile:0:0: information: Active checkers: 161/592 (use --checkers-report=<filename> to see details) [checkersReport]

Should I tweak my command somehow?