Re: Git compile warnings (under mac/clang)

From: Jeff King <peff@peff.net>
Date: Jan 22, 2015, 22:01 UTC
Message-ID: <20150122220140.GB6695@peff.net>
In-Reply-To: <b2cbad0d8e59a0c4eb0565608f3f90bc@www.dscho.org>

On Thu, Jan 22, 2015 at 10:20:01PM +0100, Johannes Schindelin wrote:

Show 17 quoted lines

> On 2015-01-22 20:59, Stefan Beller wrote:
> > cc Johannes Schindelin <Johannes.Schindelin@gmx.de> who is working in
> > the fsck at the moment
> >
> > On Thu, Jan 22, 2015 at 11:43 AM, Michael Blume <blume.mike@gmail.com> wrote:
> >
> >>     CC fsck.o
> >> fsck.c:110:38: warning: comparison of unsigned enum expression >= 0 is
> >> always true [-Wtautological-compare]
> >>         if (options->msg_severity && msg_id >= 0 && msg_id < FSCK_MSG_MAX)
> >>                                      ~~~~~~ ^  ~
> 
> According to A2.5.4 of The C Programming Language 2nd edition:
> 
>     Identifiers declared as enumerators (see Par.A.8.4) are constants of type int.
> 
> Therefore, the warning is incorrect: any assumption about enum fsck_msg_id to be unsigned is false.

I'm not sure that made it to ANSI. C99 says (setion 6.7.2.2, paragraph 4):

  Each enumerated type shall be compatible with char, a signed integer
  type, or an unsigned integer type. The choice of type is
  implementation-defined, but shall be capable of representing the
  values of all the members of the enumeration.

I don't have a copy of C89, but this isn't mentioned in the (very cursory) list of changes found in C99. Anyway, that's academic.

I think we dealt with a similar situation before, in 3ce3ffb840a1dfa7fcbafa9309fab37478605d08.

-Peff