On Wed, Oct 26, 2016 at 01:16:13AM +0200, Andreas Cadhalpun wrote: > On 25.10.2016 23:34, Carl Eugen Hoyos wrote: > > 2016-10-25 19:19 GMT+02:00 Andreas Cadhalpun > > <andreas.cadhal...@googlemail.com>: > > > >> + # LTO could optimize out the test functions without this > >> + echo "#if defined(__GNUC__) && __GNUC__ >= 4" > >> + echo " #define USED __attribute__((used))" > >> + echo "#else" > >> + echo " #define USED" > >> + echo "#endif" > > > > Why is the ugly #if - #else - #endif necessary? > > I'm under the impression that __attribute__((used)) is not available for all > compilers, > see e.g. libavutil/attributes.h. > But thinking more about it, a better way is to actually use the functions so > that > LTO can't optimize them out. This avoids the ugly preprocessor checks. > > > Please mention ticket #5909 if it is related. > > Sure, new patch attached. > > By the way, this is not a regression in 3.1.5, but a fix included in that > release allowed them to drop their distro-specific patch, exposing the problem > with LTO. > > Best regards, > Andreas >
> configure | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > 742684cf379693d08075d43fdfb75ed5e2e936c6 > 0001-configure-make-sure-LTO-does-not-optimize-out-the-te.patch > From bb289a0b2b0948afa99227bcff188301c1143624 Mon Sep 17 00:00:00 2001 > From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > Date: Tue, 25 Oct 2016 19:09:46 +0200 > Subject: [PATCH] configure: make sure LTO does not optimize out the test > functions > > Fixes trac ticket #5909 > > Bud-Id: https://bugs.gentoo.org/show_bug.cgi?id=598054 > Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > --- > configure | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/configure b/configure > index 481f692..54faef1 100755 > --- a/configure > +++ b/configure > @@ -1150,7 +1150,12 @@ check_func_headers(){ > for func in $funcs; do > echo "long check_$func(void) { return (long) $func; }" > done > - echo "int main(void) { return 0; }" > + echo "int main(void) { int ret = 0;" > + # LTO could optimize out the test functions without this > + for func in $funcs; do > + echo " ret |= ((intptr_t)check_$func) & 0xFFFF;" > + done > + echo "return ret; }" breaks configure i get this: ERROR: LoadLibrary/dlopen not found for avisynth If you think configure made a mistake, make sure you are using the latest version from Git. If the latest version fails, report the problem to the ffmpeg-u...@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net. Include the log file "config.log" produced by configure as this will help solve the problem. [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement. For even the very wise cannot see all ends. -- Gandalf
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