On Thu, Dec 01, 2016 at 09:39:22AM +0800, Wangnan (F) wrote: > > > 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? cool, thanks for finding this.. I'm about to post a fix for perf build tools anyway, so we're ok with this ccache version jirka
