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Re: enum and macro collision
- From: vijay nag <vijunag at gmail dot com>
- To: Jonathan Wakely <jwakely dot gcc at gmail dot com>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Tue, 17 Jan 2017 16:42:20 +0530
- Subject: Re: enum and macro collision
- Authentication-results: sourceware.org; auth=none
- References: <CAKhyrx8qVfNmyHPEb1RGH=x=japHc__HQPFG3yoiu7N_6tVP5Q@mail.gmail.com> <CAH6eHdTe=83orEkMQP46W1rfvDiy0O2efcDPwgj0+rwb=nQFfg@mail.gmail.com>
On Tue, Jan 17, 2017 at 4:36 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 17 January 2017 at 11:03, vijay nag wrote:
>> Hello Gcc,
>>
>> I came across this nasty C code of an enumerator and a macro having
>> the same name. Although this is a buggy code, I found it surprising
>> that GCC compiles in one of the cases(snippet 1) while in the other
>> compiler flags an error(snippet 2). Would be interested to know why
>> the order of definitions/declarations matter and what C standards the
>> compiler is adhering to ?
>
> Just look at the preprocessed code, it should be obvious.
>
> Macros aren't defined until they're defined.
>
> When the macro is defined after the enumerator it can't change it and
> you get a valid enumerator definition, FOO = 1.
>
> When the macro is defined earlier it produces an invalid enumerator,
> 0xDEADBEEF = 1
>
> What isn't clear?
Thanks for the reply, it is clear now. So, can enum have same name as
that of a macro and Is it allowed in C ?