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Build: Don't put GNU/Linux-specific symbol versions into static liblzma.

It not only makes no sense to put symbol versions into a static library
but it can also cause breakage.

By default Libtool #defines PIC if building a shared library and
doesn't define it for static libraries. This is documented in the
Libtool manual. It can be overriden using --with-pic or --without-pic.
configure.ac detects if --with-pic or --without-pic is used and then
gives an error if neither --disable-shared nor --disable-static was
used at the same time. Thus, in normal situations it works to build
both shared and static library at the same time on GNU/Linux,
only --with-pic or --without-pic requires that only one type of
library is built.

Thanks to John Paul Adrian Glaubitz from Debian for reporting
the problem that occurred on ia64:
https://www.mail-archive.com/xz-devel@tukaani.org/msg00610.html
This commit is contained in:
Lasse Collin 2022-11-24 14:52:44 +02:00
parent e1acf71072
commit 06824396b2
3 changed files with 111 additions and 49 deletions

View file

@ -477,7 +477,10 @@ elseif(BUILD_SHARED_LIBS AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
# because it would put symbol versions into the static library which
# can cause problems. It's clearer if all symver related things are
# omitted when not building a shared library.
target_compile_definitions(liblzma PRIVATE HAVE_SYMBOL_VERSIONS_LINUX)
#
# NOTE: Set it explicitly to 1 to make it clear that versioning is
# done unconditionally in the C files.
target_compile_definitions(liblzma PRIVATE HAVE_SYMBOL_VERSIONS_LINUX=1)
target_link_options(liblzma PRIVATE
"-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/src/liblzma/liblzma_linux.map"
)

View file

@ -520,54 +520,6 @@ AC_ARG_ENABLE([doc], [AS_HELP_STRING([--disable-doc],
AM_CONDITIONAL([COND_DOC], [test x$enable_doc != xno])
#####################
# Symbol versioning #
#####################
AC_MSG_CHECKING([if library symbol versioning should be used])
AC_ARG_ENABLE([symbol-versions], [AS_HELP_STRING([--enable-symbol-versions],
[Use symbol versioning for liblzma. Enabled by default on
GNU/Linux, other GNU-based systems, and FreeBSD.])],
[], [enable_symbol_versions=auto])
if test "x$enable_symbol_versions" = xauto; then
case $host_os in
# NOTE: Even if one omits -gnu on GNU/Linux (e.g.
# i486-slackware-linux), configure will (via config.sub)
# append -gnu (e.g. i486-slackware-linux-gnu), and this
# test will work correctly.
gnu* | *-gnu* | freebsd*)
enable_symbol_versions=yes
;;
*)
enable_symbol_versions=no
;;
esac
fi
AC_MSG_RESULT([$enable_symbol_versions])
# There are two variants for symbol versioning.
# See src/liblzma/validate_map.sh for details.
if test "x$enable_symbol_versions" = xyes; then
case $host_os in
linux*)
enable_symbol_versions=linux
AC_DEFINE([HAVE_SYMBOL_VERSIONS_LINUX], [1],
[Define to 1 to if GNU/Linux-specific details
are wanted for symbol versioning. This must
be used together with liblzma_linux.map.])
;;
*)
enable_symbol_versions=generic
;;
esac
fi
AM_CONDITIONAL([COND_SYMVERS_LINUX],
[test "x$enable_symbol_versions" = xlinux])
AM_CONDITIONAL([COND_SYMVERS_GENERIC],
[test "x$enable_symbol_versions" = xgeneric])
##############
# Sandboxing #
##############
@ -715,6 +667,101 @@ LT_LANG([Windows Resource])
# libs as shared.
AM_CONDITIONAL([COND_SHARED], [test "x$enable_shared" != xno])
#####################
# Symbol versioning #
#####################
# NOTE: This checks if we are building shared or static library
# and if --with-pic or --without-pic was used. Thus this check
# must be after Libtool initialization.
AC_MSG_CHECKING([if library symbol versioning should be used])
AC_ARG_ENABLE([symbol-versions], [AS_HELP_STRING([--enable-symbol-versions],
[Use symbol versioning for liblzma. Enabled by default on
GNU/Linux, other GNU-based systems, and FreeBSD.])],
[], [enable_symbol_versions=auto])
if test "x$enable_symbol_versions" = xauto; then
case $host_os in
# NOTE: Even if one omits -gnu on GNU/Linux (e.g.
# i486-slackware-linux), configure will (via config.sub)
# append -gnu (e.g. i486-slackware-linux-gnu), and this
# test will work correctly.
gnu* | *-gnu* | freebsd*)
enable_symbol_versions=yes
;;
*)
enable_symbol_versions=no
;;
esac
fi
# There are two variants for symbol versioning.
# See src/liblzma/validate_map.sh for details.
#
# On GNU/Linux, extra symbols are added in the C code. These extra symbols
# must not be put into a static library as they can cause problems (and
# even if they didn't cause problems, they would be useless). On other
# systems symbol versioning may be used too but there is no problem as only
# a linker script is specified in src/liblzma/Makefile.am and that isn't
# used when creating a static library.
#
# Libtool always uses -DPIC when building shared libraries by default and
# doesn't use it for static libs by default. This can be overriden with
# --with-pic and --without-pic though. As long as neither --with-pic nor
# --without-pic is used then we can use #ifdef PIC to detect if the file is
# being built for a shared library.
if test "x$enable_symbol_versions" = xno ; then
enable_symbol_versions=no
AC_MSG_RESULT([no])
elif test "x$enable_shared" = xno ; then
enable_symbol_versions=no
AC_MSG_RESULT([no (not building a shared library)])
else
case $host_os in
linux*)
case "$pic_mode-$enable_static" in
default-*)
# Use symvers if PIC is defined.
have_symbol_versions_linux=2
;;
*-no)
# Not building static library.
# Use symvers unconditionally.
have_symbol_versions_linux=1
;;
*)
AC_MSG_RESULT([])
AC_MSG_ERROR([
On GNU/Linux, building both shared and static library at the same time
is not supported if --with-pic or --without-pic is used.
Use either --disable-shared or --disable-static to build one type
of library at a time. If both types are needed, build one at a time,
possibly picking only src/liblzma/.libs/liblzma.a from the static build.])
;;
esac
enable_symbol_versions=linux
AC_DEFINE_UNQUOTED([HAVE_SYMBOL_VERSIONS_LINUX],
[$have_symbol_versions_linux],
[Define to 1 to if GNU/Linux-specific details
are unconditionally wanted for symbol
versioning. Define to 2 to if these are wanted
only if also PIC is defined (allows building
both shared and static liblzma at the same
time with Libtool if neither --with-pic nor
--without-pic is used). This define must be
used together with liblzma_linux.map.])
;;
*)
enable_symbol_versions=generic
;;
esac
AC_MSG_RESULT([yes ($enable_symbol_versions)])
fi
AM_CONDITIONAL([COND_SYMVERS_LINUX],
[test "x$enable_symbol_versions" = xlinux])
AM_CONDITIONAL([COND_SYMVERS_GENERIC],
[test "x$enable_symbol_versions" = xgeneric])
###############################################################################
# Checks for libraries.

View file

@ -34,6 +34,18 @@
#include "lzma.h"
// The extra symbol versioning in the C files may only be used when
// building a shared library. If HAVE_SYMBOL_VERSIONS_LINUX is defined
// to 2 then symbol versioning is done only if also PIC is defined.
// By default Libtool defines PIC when building a shared library and
// doesn't define it when building a static library but it can be
// overriden with --with-pic and --without-pic. configure let's rely
// on PIC if neither --with-pic or --without-pic was used.
#if defined(HAVE_SYMBOL_VERSIONS_LINUX) \
&& (HAVE_SYMBOL_VERSIONS_LINUX == 2 && !defined(PIC))
# undef HAVE_SYMBOL_VERSIONS_LINUX
#endif
#ifdef HAVE_SYMBOL_VERSIONS_LINUX
// To keep link-time optimization (LTO, -flto) working with GCC,
// the __symver__ attribute must be used instead of __asm__(".symver ...").