libctf: try several possibilities for linker versioning flags

Checking for linker versioning by just grepping ld --help output for
mentions of --version-script is inadequate now that Solaris 11.4
implements a --version-script with different semantics.  Try linking a
test program with a small wildcard-using version script with each
supported set of flags in turn, to make sure that linker versioning is
not only advertised but actually works.

The Solaris "GNU-compatible" linker versioning is not quite
GNU-compatible enough, but we can work around the differences by
generating a new version script that removes the comments from the
original (Solaris ld requires #-style comments), and making another
version script for libctf-nonbfd in particular which doesn't mention any
of the symbols that appear in libctf.la, to avoid Solaris ld introducing
corresponding new NOTYPE symbols to match the version script.

libctf/ChangeLog
2021-09-27  Nick Alcock  <nick.alcock@oracle.com>

	PR libctf/27967
	* configure.ac (VERSION_FLAGS): Replace with...
	(ac_cv_libctf_version_script): ... this multiple test.
	(VERSION_FLAGS_NOBFD): Substitute this too.
	* Makefile.am (libctf_nobfd_la_LDFLAGS): Use it.  Split out...
	(libctf_ldflags_nover): ... non-versioning flags here.
	(libctf_la_LDFLAGS): Use it.
	* libctf.ver: Give every symbol not in libctf-nobfd a comment on
	the same line noting as much.

1 files changed, 43 insertions, 3 deletions

diff --git a/libctf/configure.ac b/libctf/configure.ac
index 80644b8..4e12a4f 100644
--- a/libctf/configure.ac
+++ b/libctf/configure.ac
@@ -219,11 +219,51 @@ fi`
 AM_CONDITIONAL(TCL_TRY, test "${ac_cv_libctf_tcl_try}" = yes)
 
 # Use a version script, if possible, or an -export-symbols-regex otherwise.
-VERSION_FLAGS='-export-symbols-regex ctf_.*'
-if $LD --help 2>&1 | grep -- --version-script >/dev/null; then
-    VERSION_FLAGS="-Wl,--version-script='$srcdir/libctf.ver'"
+decommented_version_script=
+AC_CACHE_CHECK([for linker versioning flags], [ac_cv_libctf_version_script],
+  [echo 'FOO { global: mai*; local: ctf_fo*; };' > conftest.ver
+   old_LDFLAGS="$LDFLAGS"
+   old_CFLAGS="$CFLAGS"
+   LDFLAGS="$LDFLAGS -shared -Wl,--version-script=conftest.ver"
+   CFLAGS="$CFLAGS -fPIC"
+   AC_LINK_IFELSE([AC_LANG_SOURCE([[int ctf_foo (void) { return 0; }
+				    int main (void) { return ctf_foo(); }]])],
+		  [ac_cv_libctf_version_script="-Wl,--version-script='$srcdir/libctf.ver'"],
+		  [])
+   LDFLAGS="$old_LDFLAGS"
+
+   if test -z "$ac_cv_libctf_version_script"; then
+     LDFLAGS="$LDFLAGS -shared -Wl,-B,local -Wl,-z,gnu-version-script=conftest.ver"
+     AC_LINK_IFELSE([AC_LANG_SOURCE([[int ctf_foo (void) { return 0; }
+				      int main (void) { return ctf_foo(); }]])],
+		    [ac_cv_libctf_version_script="-Wl,-B,local -Wl,-z,gnu-version-script"
+		     decommented_version_script=t],
+		    [])
+     LDFLAGS="$old_LDFLAGS"
+   fi
+   CFLAGS="$old_CFLAGS"
+
+   if test -z "$ac_cv_libctf_version_script"; then
+     ac_cv_libctf_version_script='-export-symbols-regex ctf_.*'
+   fi
+   rm -f conftest.ver])
+if test -n "$decommented_version_script"; then
+   # Solaris's version scripts use shell-style comments rather than the C-style
+   # used by GNU ld.  Use cpp to strip the comments out.  (cpp exists under this
+   # name on all platforms that support ld -z gnu-version-script.)
+   # Also ensure that no symbols exist in the version script for libctf-nobfd.so
+   # that do not exist in the shared library itself, since some linkers add such
+   # symbols with type NOTYPE.
+   /lib/cpp < $srcdir/libctf.ver > libctf-decommented.ver
+   grep -v 'libctf only' $srcdir/libctf.ver | /lib/cpp > libctf-nobfd-decommented.ver
+   VERSION_FLAGS="$ac_cv_libctf_version_script='libctf-decommented.ver'"
+   VERSION_FLAGS_NOBFD="$ac_cv_libctf_version_script='libctf-nobfd-decommented.ver'"
+else
+   VERSION_FLAGS="$ac_cv_libctf_version_script"
+   VERSION_FLAGS_NOBFD="$ac_cv_libctf_version_script"
 fi
 AC_SUBST(VERSION_FLAGS)
+AC_SUBST(VERSION_FLAGS_NOBFD)
 
 AC_CONFIG_FILES(Makefile)
 AC_CONFIG_HEADERS(config.h)