[Bug 856839] Re: libglib2.0-0 fails to build using dpkg-buildpackage when added "-flto" to CFLAGS and LDFLAGS

[Julian Taylor]

the build fails with glib 2.29.92-0ubuntu1 gcc-4.6 4.6.1-9ubuntu3 and binutils 2.21.53.20110810-0ubuntu3 with flto applied to compilation and linking stage:
dpkg-buildpackage config
APPEND CFLAGS -flto
APPEND LDFLAGS -flto

See the attached buildlog

It succeeds without -flto.

When building with -U_FORTIFY_SOURCE the linking failure is solved but one gets this error:
gcc -DHAVE_CONFIG_H -I. -I/tmp/glib2.0-2.29.92/./glib/tests -I../.. -g -I../.. -I../../glib -I/tmp/glib2.0-2.29.92/./glib -I/tmp/glib2.0-2.29.92/. -DSRCDIR=\""/tmp/glib2.0-2.29.92/./glib/tests"\" -DG_ENABLE_DEBUG  -DG_DISABLE_SINGLE_INCLUDES -pthread  -g -O2 -flto  -U_FORTIFY_SOURCE -Wall -c /tmp/glib2.0-2.29.92/./glib/tests/mem-overflow.c
/tmp/glib2.0-2.29.92/./glib/tests/mem-overflow.c:137:1: sorry, unimplemented: gimple bytecode streams do not support the optimization attribute

** Attachment added: "-flto added to default flags"
   https://bugs.launchpad.net/ubuntu/+source/binutils/+bug/856839/+attachment/2443193/+files/glib-default%2Blto.buildlog

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https://bugs.launchpad.net/bugs/856839

Title:
  libglib2.0-0 fails to build using dpkg-buildpackage when added "-flto"
  to CFLAGS and LDFLAGS

Status in “binutils” package in Ubuntu:
  Confirmed
Status in “gcc-4.6” package in Ubuntu:
  Confirmed
Status in “glib2.0” package in Ubuntu:
  Confirmed

Bug description:
  when using apt-get source libglib2.0-0, and adding -flto to the CFLAGS
  and LDFLAGS, the build fails with this:

  ./.libs/libglib-2.0.so: undefined reference to `__open_too_many_args'
  ./.libs/libglib-2.0.so: undefined reference to `__open_missing_mode'

  which are errors generated by FORTIFY_SOURCE. it's currently unknown
  if these are true positives from FORTIFY_SOURCE that are somehow
  missed without LTO, or are false positives due to codegen issues when
  enabling LTO.

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