Re: bug: "gcc -std=gnu99" passes AC_PROG_CC_C11

[Adrian Bunk]

On Tue, Sep 25, 2012 at 05:57:08PM -0700, Paul Eggert wrote:
> On 09/25/2012 05:04 PM, Adrian Bunk wrote:
> > If a future gcc version
> > ...
> > supports C11 features in gnu11 mode it doesn't support in
> > gnu99 mode (likely)
> 
> I don't see this as likely, as I don't see any such features on the
> horizon.  (I am excluding gets, which we don't want to be encouraging anyway.)

You assume gnu99 will always include all features of gnu11?

> > Currently gcc is the only compiler where autoconf knows how to put it 
> > into C11 mode, and __STDC_VERSION__ is defined in gnu11 mode.
> 
> But gcc normally doesn't define __STDC_VERSION__.  Granted,
> gcc --std=gnu11 does define it, but all in all __STDC_VERSION__
> is a bit squirrelly and I'd rather not be using it as part of a test.

gcc defines __STDC_VERSION__ except for pre-C94 modes like gnu89 (which 
is the default), since __STDC_VERSION__ was not defined in the original C89.

Notes:
- we are discussing here only C11 mode detection and setting
- currently gcc >= 4.7 is the only compiler supported for that in 
  autoconf
- there is the option to make that part of the check  gcc-only later if 
  it would turn out that this is needed when C11 setting  for other 
  compilers will get added.

cu
Adrian

-- 

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       "Only a promise," Lao Er said.
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