The -Wp,M options behaviour change

[Wangnan (F)]

On 2016/11/30 22:49, Jiri Olsa wrote:
> On Tue, Nov 29, 2016 at 02:31:36PM +0100, Jiri Olsa wrote:
>> hi,
>> we noticed behaviour change in Fedora 25 gcc wrt -Wp option.
>>
>> We use following command line to generate the dependency file:
>>    gcc -Wp,-MD,krava,-MT,krava -c -o ex.o ex.c
>>
>> and we get 'krava' file with:
>>    krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
>>
>> But when we split -Wp option into 2 -Wp options like:
>>    gcc -Wp,-MD,krava -Wp,MT,krava -c -o ex.o ex.c
>>
>> we get:
>>    ex.o krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
>>
>> notice the extra 'ex.o' target.
>>
>> We see this behaviour in Fedora 25. It's ok in Fedora 24, which seems odd
>> because both have same gcc version 6.2.1. Please check full output below.
> more info on this.. it's not fedora version related, it's related
> to having ccache installed (kudos to Arnaldo ;-) )
>
> with ccache installed above behaviour happens in both Fedora 24 and 25

Find in ccache releasenotes (https://ccache.samba.org/releasenotes.html)

ccache 3.3.2

Release date: 2016-09-28

Bug fixes
Fixed a regression in ccache 3.3 related to potentially bad content of 
dependency files when compiling identical source code but with different 
source paths.

Fixed a regression in ccache 3.3.1: ccache could get confused when using 
the compiler option -Wp, to pass multiple options to the preprocessor, 
resulting in missing dependency files from direct mode cache hits.

So please try a newer ccache and see the result?

> thanks,
> jirka