[libvirt] [PATCHv3 1/3] build: Check for broken GCC -Wlogical-op in configure

[Daniel P. Berrange]

On Wed, Dec 19, 2012 at 11:14:15AM +0100, Viktor Mihajlovski wrote:
> On 12/18/2012 09:38 PM, Eric Blake wrote:
> >
> >I know this is already pushed, but I think it would fit better under
> >m4/virt-compile-warnings.m4 rather than at the top-level configure.ac.
> >
> since it is early in the release it's not too late to change this,
> although I think - if not in configure.ac - it would rather belong
> to a separate m4/workarounds.m4 or similar ...
> >Potential ouch.  This sets BROKEN_GCC_WLOGICALOP to 1 on all non-gcc
> >compilers.  Then in patch 2/3, you blindly use this condition to request
> >a pragma:
> Really? My expectation is that only a GCC compiler will trigger this
> condition unless there are other compilers producing a compile error
> with strchr(x,y).
> In consequence it is fair to use a GCC pragma, especially as the
> diagnostic pragma is applicable for the failing GCC versions (according
> to the GCC manuals).

I think Eric means that on non-GCC this code:

# if BROKEN_GCC_WLOGICALOP
#  pragma GCC diagnostic ignored "-Wlogical-op"
# endif


will cause the compiler to complain "Unknown pragma GCC diagnostic..."
since obviously non-GCC compilers don't understand GCC pragmas

Daniel
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