Re: Status of undef warnings fix?

[Will Newton <will dot newton at linaro dot org>]

On 25 April 2014 21:25, Steve Ellcey <sellcey@mips.com> wrote:
> On Fri, 2014-04-25 at 20:06 +0100, Will Newton wrote:
>> On 25 April 2014 19:03, Steve Ellcey <sellcey@mips.com> wrote:
>> >
>> > I was wondering what the status of the patches to fix the various
>> > undef warnings in the glibc build was.  I.e.:
>> >
>> > ../sysdeps/generic/ldsodefs.h:536:24: warning: "HP_SMALL_TIMING_AVAIL" is not defined [-Wundef]
>> >
>> > I am getting 1665 of them during one build of glibc.
>> >
>> > I see a set of patches that were submitted last month by Will Newton,
>> > https://sourceware.org/ml/libc-alpha/2014-03/msg00476.html for
>> > example.  But it doesn't look like they have been checked in yet.
>>
>> I reverted the patches as they were not the correct approach.
>> Unfortunately for the majority of the warnings nobody has stepped up
>> to implement the correct approach.
>
> Do you have a pointer to what is considered 'the correct approach'.  I
> tried reading through the email to find it but got lost in a maze of
> twisty replies.

My understanding is we want to use #if rather than #ifdef as far as
possible so if someone typos a #define then the #if will cause a
compile time warning rather than silently being treated as undefined.

This means that rather than having a preprocessor symbol defined or
not defined by an architecture to enable a feature the symbol should
be defined to either 1 or 0 in every architecture. So to fix some of
these warnings correctly involves cross-architecture patches and
knowledge of how sysdeps works which I think partly explains why they
are taking so long to fix.

-- 
Will Newton
Toolchain Working Group, Linaro