[cairo-bugs] [Bug 63310] New: x11-libs/cairo-1.12.12 fails to compile using clang+lto

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=63310

          Priority: medium
            Bug ID: 63310
          Assignee: chris at chris-wilson.co.uk
           Summary: x11-libs/cairo-1.12.12 fails to compile using
                    clang+lto
        QA Contact: cairo-bugs at cairographics.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: abendstund at gmail.com
          Hardware: All
            Status: NEW
           Version: 1.12.12
         Component: general
           Product: cairo

Created attachment 77662
  --> https://bugs.freedesktop.org/attachment.cgi?id=77662&action=edit
cairo-1.12.12-make-ac-float-endianess-test-llvm-bitcode-save.patch

I've posted this to bugs.gentoo.org before
  https://bugs.gentoo.org/show_bug.cgi?id=464982

As requested there, I repost the patches here. There are two issues I
encountered when compiling cairo with "clang -O4":

1) bitcode representation of object files makes float endianess test in
configure break (see attached patch)

2) "automatic configuration" of pthreads does not work while explicitly
--enable-pthread=yes to configure does

If "--enable-pthread=yes" configure option is not passed, the default is "auto"
instead of "yes", which basically runs the first block of the following lines
in
  cairo-1.12.12/build/configure.ac.pthread (around line 220)
-- >8 --
    dnl Check if we can use libc's stubs in libcairo.
    dnl Only do this if the user hasn't explicitly enabled
    dnl pthreads, but is relying on automatic configuration.
    have_pthread="no"
    if test "x$enable_pthread" != "xyes"; then
        CAIRO_CHECK_PTHREAD(
            [pthread], [-D_REENTRANT], [],
            [libcairo_pthread_program],
            [have_pthread=yes],
            [])
    fi

    dnl Default to using the real pthreads for libcairo.
    if test "x$have_pthread" != "xyes"; then
        have_pthread="$have_real_pthread";
        pthread_CFLAGS="$real_pthread_CFLAGS";
        pthread_LIBS="$real_pthread_LIBS";
    fi
-- >8 --

This automatic configuration apparently does not work if clang -O4 is used,
even though libcairo_pthread_program seems to succeed.

Or in other words: using libc stubs as a pthread provider currently does not
work if clang -O4 is in use, the automatically configured stubs make the
compile quit with

libtool: link: clang -march=native -pipe -fomit-frame-pointer -O4
-finline-limit=1200 -march=native -pipe -fomit-frame-pointer -O4 -Wl,-O1
-Wl,--hash-style=gnu -Wl,--sort-common -Wl,-z -Wl,norelro -o
.libs/cairo-analyse-trace cairo-analyse-trace.o cairo-error.o  -Wl,--as-needed
../util/cairo-script/.libs/libcairo-script-interpreter.so
../util/cairo-missing/.libs/libcairo-missing.a ./.libs/libcairoperf.a
../boilerplate/.libs/libcairoboilerplate.a
/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/src/.libs/libcairo.so
../src/.libs/libcairo.so -lpixman-1 -lfontconfig -lfreetype -lEGL -ldl -lpng15
-lxcb-shm -lxcb-render -lxcb -lXrender -lX11 -lXext -lz -lGL -lOpenVG -lrt -lm
/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/src/.libs/libcairo.so:
error: undefined reference to 'pthread_mutexattr_settype'
/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/src/.libs/libcairo.so:
error: undefined reference to 'pthread_mutexattr_init'
/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/src/.libs/libcairo.so:
error: undefined reference to 'pthread_mutexattr_destroy'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[4]: *** [cairo-analyse-trace] Error 1
make[4]: Leaving directory
`/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/perf'
make[3]: Leaving directory
`/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/perf'
make[2]: Leaving directory
`/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12/perf'
make[3]: *** [all-recursive] Error 1
make[2]: *** [all] Error 2
make[1]: Leaving directory
`/var/tmp/paludis/x11-libs-cairo-1.12.12-r1/work/cairo-1.12.12'
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2



I'm unsure about a proper fix for this, but thought about
  - patch configure.ac.pthread to use real_pthread as an automatic
configuration
    i.e. throw out libc stubs, use real_pthread if libcairo_pthread_program 

Thanks

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