[PATCH 1/3] Use AX_CHECK_VSCRIPT to test for version script support
Kevin Cernekee
cernekee at gmail.com
Sat Dec 6 23:01:19 PST 2014
AX_CHECK_VSCRIPT improves on the current detection method by adding a
new check for false positives. On OSX, the current check fails, but only
by accident:
configure:14730: checking if library symbol versioning is available
configure:14734: gcc -c -g -O2 conftest.c >&5
configure:14737: $? = 0
configure:14741: gcc -dynamiclib ${wl}-undefined ${wl}dynamic_lookup -o conftest.o -install_name /conftest -Wl,--version-script -Wl,conftest.map
clang: error: no such file or directory: '${wl}-undefined'
clang: error: no such file or directory: '${wl}dynamic_lookup'
configure:14744: $? = 1
configure:14749: gcc -dynamiclib ${wl}-undefined ${wl}dynamic_lookup -o conftest.o -install_name /conftest -Wl,-M -Wl,conftest.map
clang: error: no such file or directory: '${wl}-undefined'
clang: error: no such file or directory: '${wl}dynamic_lookup'
configure:14752: $? = 1
configure:14759: result: no
Passing -Wl,-M,conftest.map on OSX may or may not actually cause a build
failure:
$ gcc conftest.c -o conftest -Wl,-M,conftest.map ; echo $?
ld: warning: ignoring file conftest.map, file was built for unsupported file format ( 0x56 0x31 0x20 0x7B 0x20 0x67 0x6C 0x6F 0x62 0x61 0x6C 0x3A 0x20 0x24 0x32 0x3B ) which is not the architecture being linked (x86_64): conftest.map
0
$ gcc conftest.c -o conftest -Wl,-M,conftest-short.map ; echo $?
ld: file too small (length=2) file 'conftest-short.map' for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
1
After getting a successful result from the above -M check,
AX_CHECK_VSCRIPT will try another version script containing syntax errors.
It will report a failure (unsupported) if the linker still accepts the
malformed script.
Signed-off-by: Kevin Cernekee <cernekee at gmail.com>
---
Makefile.am | 4 +-
configure.ac | 30 +----------
m4/ax_check_vscript.m4 | 142 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 145 insertions(+), 31 deletions(-)
create mode 100644 m4/ax_check_vscript.m4
diff --git a/Makefile.am b/Makefile.am
index d817afb..0a38785 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -75,8 +75,8 @@ endif
libopenconnect_la_LDFLAGS = $(LT_VER_ARG) @APIMAJOR@:@APIMINOR@ -no-undefined
noinst_HEADERS = openconnect-internal.h openconnect.h gnutls.h
include_HEADERS = openconnect.h
-if HAVE_SYMBOL_VERSIONING
-libopenconnect_la_LDFLAGS += -Wl, at VERSION_SCRIPT_ARG@,libopenconnect.map
+if HAVE_VSCRIPT
+libopenconnect_la_LDFLAGS += @VSCRIPT_LDFLAGS@,libopenconnect.map
libopenconnect_la_DEPENDENCIES = libopenconnect.map
endif
diff --git a/configure.ac b/configure.ac
index d55b743..047b1c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -520,35 +520,7 @@ if test "$use_openbsd_libtool" = "true" && test -x /usr/bin/libtool; then
fi
AM_CONDITIONAL(OPENBSD_LIBTOOL, [ test "$use_openbsd_libtool" = "true" ])
-# Ick. This seems like it's likely to be very fragile, but I can't see a better
-# way. I shall console myself with the observation that the failure mode isn't
-# particularly horrible — you just don't get symbol versioning if it fails.
-
-AC_ARG_ENABLE([symvers],
- AS_HELP_STRING([--disable-symvers],
- [disable library symbol versioning [default=auto]]),
- [want_symvers=$enableval],
- [want_symvers=yes])
-
-symvers=no
-if test "$enable_shared" = "yes" -a "$want_symvers" != "no" ; then
- AC_MSG_CHECKING([if library symbol versioning is available]);
- echo 'FOO { global: foo; local: *; };' > conftest.map
- echo 'int foo = 0;' > conftest.$ac_ext
- if AC_TRY_EVAL(ac_compile); then
- soname=conftest
- libobjs=conftest.$ac_objext
- if AC_TRY_EVAL(archive_cmds ${wl}--version-script ${wl}conftest.map); then
- AC_SUBST(VERSION_SCRIPT_ARG, [--version-script])
- symvers="yes (with --version-script)"
- elif AC_TRY_EVAL(archive_cmds ${wl}-M ${wl}conftest.map); then
- AC_SUBST(VERSION_SCRIPT_ARG, [-M])
- symvers="yes (with -M)"
- fi
- fi
- AC_MSG_RESULT(${symvers})
-fi
-AM_CONDITIONAL(HAVE_SYMBOL_VERSIONING, [test "${symvers}" != "no"])
+AX_CHECK_VSCRIPT
PKG_CHECK_MODULES(LIBXML2, libxml-2.0)
diff --git a/m4/ax_check_vscript.m4 b/m4/ax_check_vscript.m4
new file mode 100644
index 0000000..030da18
--- /dev/null
+++ b/m4/ax_check_vscript.m4
@@ -0,0 +1,142 @@
+# ===========================================================================
+# http://www.gnu.org/software/autoconf-archive/ax_check_vscript.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_CHECK_VSCRIPT
+#
+# DESCRIPTION
+#
+# Check whether the linker supports version scripts. Version scripts are
+# used when building shared libraries to bind symbols to version nodes
+# (helping to detect incompatibilities) or to limit the visibility of
+# non-public symbols.
+#
+# Output:
+#
+# If version scripts are supported, VSCRIPT_LDFLAGS will contain the
+# appropriate flag to pass to the linker. On GNU systems this would
+# typically be "-Wl,--version-script", and on Solaris it would
+# typically be "-Wl,-M".
+#
+# Two Automake conditionals are also set:
+#
+# HAVE_VSCRIPT is true if the linker supports version scripts with
+# entries that use simple wildcards, like "local: *".
+#
+# HAVE_VSCRIPT_COMPLEX is true if the linker supports version scripts with
+# pattern matching wildcards, like "global: Java_*".
+#
+# On systems that do not support symbol versioning, such as Mac OS X, both
+# conditionals will be false. They will also be false if the user passes
+# "--disable-symvers" on the configure command line.
+#
+# Example:
+#
+# configure.ac:
+#
+# AX_CHECK_VSCRIPT
+#
+# Makefile.am:
+#
+# if HAVE_VSCRIPT
+# libfoo_la_LDFLAGS += $(VSCRIPT_LDFLAGS), at srcdir@/libfoo.map
+# endif
+#
+# if HAVE_VSCRIPT_COMPLEX
+# libbar_la_LDFLAGS += $(VSCRIPT_LDFLAGS), at srcdir@/libbar.map
+# endif
+#
+# LICENSE
+#
+# Copyright (c) 2014 Kevin Cernekee <cernekee at gmail.com>
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice
+# and this notice are preserved. This file is offered as-is, without any
+# warranty.
+
+#serial 1
+
+# _AX_CHECK_VSCRIPT(flag, global-sym, action-if-link-succeeds, [junk-file=no])
+AC_DEFUN([_AX_CHECK_VSCRIPT], [
+ AC_LANG_PUSH([C])
+ ax_check_vscript_save_flags="$LDFLAGS"
+ echo "V1 { global: $2; local: *; };" > conftest.map
+ AS_IF([test x$4 = xyes], [
+ echo "{" >> conftest.map
+ ])
+ LDFLAGS="$LDFLAGS -Wl,$1,conftest.map"
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([[int show, hide;]], [])], [$3])
+ LDFLAGS="$ax_check_vscript_save_flags"
+ rm -f conftest.map
+ AC_LANG_POP([C])
+]) dnl _AX_CHECK_VSCRIPT
+
+AC_DEFUN([AX_CHECK_VSCRIPT], [
+
+ AC_ARG_ENABLE([symvers],
+ AS_HELP_STRING([--disable-symvers],
+ [disable library symbol versioning [default=auto]]),
+ [want_symvers=$enableval],
+ [want_symvers=yes]
+ )
+
+ AS_IF([test x$want_symvers = xyes], [
+
+ dnl First test --version-script and -M with a simple wildcard.
+
+ AC_CACHE_CHECK([linker version script flag], ax_cv_check_vscript_flag, [
+ ax_cv_check_vscript_flag=unsupported
+ _AX_CHECK_VSCRIPT([--version-script], [show], [
+ ax_cv_check_vscript_flag=--version-script
+ ])
+ AS_IF([test x$ax_cv_check_vscript_flag = xunsupported], [
+ _AX_CHECK_VSCRIPT([-M], [show], [ax_cv_check_vscript_flag=-M])
+ ])
+
+ dnl The linker may interpret -M (no argument) as "produce a load map."
+ dnl If "-M conftest.map" doesn't fail when conftest.map contains
+ dnl obvious syntax errors, assume this is the case.
+
+ AS_IF([test x$ax_cv_check_vscript_flag != xunsupported], [
+ _AX_CHECK_VSCRIPT([$ax_cv_check_vscript_flag], [show],
+ [ax_cv_check_vscript_flag=unsupported], [yes])
+ ])
+ ])
+
+ dnl If the simple wildcard worked, retest with a complex wildcard.
+
+ AS_IF([test x$ax_cv_check_vscript_flag != xunsupported], [
+ ax_check_vscript_flag=$ax_cv_check_vscript_flag
+ AC_CACHE_CHECK([if version scripts can use complex wildcards],
+ ax_cv_check_vscript_complex_wildcards, [
+ ax_cv_check_vscript_complex_wildcards=no
+ _AX_CHECK_VSCRIPT([$ax_cv_check_vscript_flag], [sh*], [
+ ax_cv_check_vscript_complex_wildcards=yes])
+ ])
+ ax_check_vscript_complex_wildcards="$ax_cv_check_vscript_complex_wildcards"
+ ], [
+ ax_check_vscript_flag=
+ ax_check_vscript_complex_wildcards=no
+ ])
+ ], [
+ AC_MSG_CHECKING([linker version script flag])
+ AC_MSG_RESULT([disabled])
+
+ ax_check_vscript_flag=
+ ax_check_vscript_complex_wildcards=no
+ ])
+
+ AS_IF([test x$ax_check_vscript_flag != x], [
+ VSCRIPT_LDFLAGS="-Wl,$ax_check_vscript_flag"
+ AC_SUBST([VSCRIPT_LDFLAGS])
+ ])
+
+ AM_CONDITIONAL([HAVE_VSCRIPT],
+ [test x$ax_check_vscript_flag != x])
+ AM_CONDITIONAL([HAVE_VSCRIPT_COMPLEX],
+ [test x$ax_check_vscript_complex_wildcards = xyes])
+
+]) dnl AX_CHECK_VSCRIPT
--
2.1.1
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