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Date: Sun, 2 Mar 2014 22:45:03 +0100
Message-ID: <CAJoYywWOHqh9qpFg3skt9XJFVoYgpa0C=g+g6mtEATiArLbgLg@mail.gmail.com>
Subject: Re: va_list and char* are ambiguous
From: Irfan Adilovic <irfanadilovic@gmail.com>
To: cygwin@cygwin.com
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On Sun, Mar 2, 2014 at 6:58 PM, Irfan Adilovic wrote:
> irfan@irfy:~$ cat x.cc
> #include <cstdarg>
> #include <iostream>
> using namespace std;
> void foo (...)        { cout << "varargs\n"; }
> void foo (va_list ap) { cout << "va_list\n"; }
> int main () {
>     foo ((const char *)NULL);
>     foo ((char *)NULL);
> }
> irfan@irfy:~$ make x
> g++     x.cc   -o x
> irfan@irfy:~$ ./x
> varargs
> va_list
> $ uname -a
> CYGWIN_NT-6.2 irfy 1.7.29(0.271/5/3) 2014-02-21 23:45 x86_64 Cygwin
>
> I would expect the varargs version of foo to be called both times --
> and it does on my linux machine -- but I get the above output under
> Cygwin. It looks like va_list is defined in terms of char*.
>
> Can anyone confirm this behavior on their Cygwin installations?
>
> Is this behavior legal? (in terms of whatever standards apply)
>
> Is there a way to "fix" this? (i.e. typedef va_list as a pointer to a
> struct defined just for the purpose of defining the va_list type)
>
> -- Irfan

I forgot to mention that calling `foo ("");` will produce:

x.cc:7:12: warning: deprecated conversion from string constant to
'char*' [-Wwrite-strings]
     foo ("");
            ^

at compile time and will end up calling va_list at runtime.

-- Irfan

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