[cfe-users] inconsistent compilation error inside constexpr if

[David Blaikie via cfe-users]

>From what I could test on godbolt, using LLVM evrsions back to 5.0,
Clang does reject the "return ClientMain();" call you aren't seeing an
error on. So I'm not sure what compiler/version/situation you're
running, but at least at first blush it doesn't look like clang.

On Fri, Aug 21, 2020 at 1:29 PM Manu agarwal via cfe-users
<cfe-users at lists.llvm.org> wrote:
>
> Hello,
>
> In the below code the compiler throws "undeclared identifier" when the commented line is uncommented. Whereas the line just before compiles fine.
>
> Regards,
> Manu
>
> typedef bool (* DummyFunc)   ();
>
>
> bool ExecDummy (DummyFunc fptr) {
>
>     if (fptr)
>         return fptr ();
>
>     return false;
> }
>
> constexpr unsigned int IsMyAppClient = 0;
>
> constexpr bool CheckForTypeClient (unsigned int pAppType)
> {
>     return ((pAppType & IsMyAppClient) != 0);
> }
>
>
> class  MyAppTemplate
> {
> public:
>     template <unsigned int T>
>     static    bool    MyAppInit ();
> };
>
> template <unsigned int T>
> bool
> MyAppTemplate::MyAppInit ()
> {
>     if constexpr (CheckForTypeClient(T)) {
>
>         return ClientMain ();                    // no error
>         //return ExecDummy(ClientMain);            // error: use of undeclared identifier 'ClientMain'
>     }
>
>     return false;
> }
>
> int __cdecl
> main (int pArgc, char* pArgv[])
> {
>     constexpr int TVal = 3;
>
>     MyAppTemplate::MyAppInit<TVal> ();
>
>     return 0;
> }
>
>
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