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Re: [RFA/symtab] Handle weak functions as global
On Sun, Nov 28, 2004 at 09:08:32PM -0500, Elena Zannoni wrote:
> Interesting. This is just gdb not following in the symbol searches any
> of the ELF scoping rules. Can you add a small testcase?
I'll have to limit it to GCC - the patch only affects weak symbols.
Here's a test case; one unexpected failure without the patch, none
with. Two known failures (see below).
> If you compile the files with bar() as shared libraries, what version
> of bar does gdb pick from main?
The right one, with or without the patch - if you link the library
contaning file1 first on the command line, it breaks in file1.c,
otherwise it breaks in file2.c. I think you could get GDB to give the
wrong answer with more complicated tests - for instance using dlopen.
Like you said, GDB doesn't know anything about ELF scoping (and I don't
think it could know everything about it, either - does the link map
expose enough information about search order?).
The only way I could get the test to work was by using a weak symbol
and building the shared libraries without debug information. This
patch only changes the minsym type; with debug information,
lookup_minimal_symbol is never called. The original problem came up
because "open" is an assembly stub in GDB.
This exposed a related problem, which I've filed as gdb/1824. If one
has debug and the other doesn't, lookup_symbol will succeed, and we'll
always breakpoint the full symbol. Global minimal symbols could
be handled before static full symbols, one object at a time. Or, as I
suggest in the bug report, we could just breakpoint both copies. I
suspect that's more robust and more useful.
Testcase look OK? I finally added some shared library utility code to
gdb.exp.
--
Daniel Jacobowitz
2004-11-30 Daniel Jacobowitz <dan@debian.org>
* gdb.base/solib-weak.c, gdb.base/solib-weak.exp, gdb.base/weaklib1.c,
gdb.base/weaklib2.c: New files.
* lib/gdb.exp (gdb_compile): Handle shlib=.
(gdb_compile_shlib): New function.
Index: testsuite/gdb.base/solib-weak.c
===================================================================
RCS file: testsuite/gdb.base/solib-weak.c
diff -N testsuite/gdb.base/solib-weak.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/solib-weak.c 30 Nov 2004 21:22:27 -0000
@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2004 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ USA. */
+
+int
+main()
+{
+ foo ();
+ return 0;
+}
Index: testsuite/gdb.base/solib-weak.exp
===================================================================
RCS file: testsuite/gdb.base/solib-weak.exp
diff -N testsuite/gdb.base/solib-weak.exp
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/solib-weak.exp 30 Nov 2004 21:28:35 -0000
@@ -0,0 +1,109 @@
+# Copyright 2004
+# Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+# Test setting breakpoints on shared library functions provided by more
+# than one shared library, when one of the implementations is a "weak"
+# symbol. GDB should set a breakpoint at the first copy it finds.
+
+# Don't try to run shared library test cases on a remote target for now.
+if ![isnative] then {
+ return 0
+}
+
+# This test uses GCC-specific syntax.
+if [get_compiler_info ${objdir}/${subdir}/solib-weak] {
+ return -1
+}
+
+if {$gcc_compiled == 0} {
+ return 0
+}
+
+proc do_test { lib1opts lib2opts lib1first } {
+ global objdir srcdir subdir
+
+ set testopts ""
+ if {$lib1opts == ""} {
+ append testopts "lib1 nodebug, "
+ } else {
+ append testopts "lib1 debug, "
+ }
+ if {$lib2opts == ""} {
+ append testopts "lib2 nodebug, "
+ } else {
+ append testopts "lib2 debug, "
+ }
+ if {$lib1first} {
+ append testopts "lib1 first"
+ } else {
+ append testopts "lib2 first"
+ }
+
+ set testfile "solib-weak"
+ set srcfile ${testfile}.c
+ set binfile ${objdir}/${subdir}/${testfile}
+
+ set libfile1 "weaklib1"
+ set libfile2 "weaklib2"
+ set lib1src ${srcdir}/${subdir}/${libfile1}.c
+ set lib2src ${srcdir}/${subdir}/${libfile2}.c
+ set lib1 ${objdir}/${subdir}/${libfile1}.sl
+ set lib2 ${objdir}/${subdir}/${libfile2}.sl
+
+ if $lib1first {
+ set exec_opts [list debug shlib=${lib1} shlib=${lib2}]
+ set expected_file ${libfile1}
+ } else {
+ set exec_opts [list debug shlib=${lib2} shlib=${lib1}]
+ set expected_file ${libfile2}
+ }
+
+ if { [gdb_compile_shlib ${lib1src} ${lib1} ${lib1opts}] != ""
+ || [gdb_compile_shlib ${lib2src} ${lib2} ${lib2opts}] != ""
+ || [gdb_compile "${srcdir}/${subdir}/${srcfile}" ${binfile} executable $exec_opts] != ""} {
+ return -1
+ }
+
+ gdb_exit
+ gdb_start
+ gdb_reinitialize_dir $srcdir/$subdir
+ gdb_load ${binfile}
+
+ runto_main
+
+ gdb_breakpoint "bar"
+
+ # If the library which will be used is compiled without debugging
+ # information, GDB will pick the wrong copy of "bar", i.e. the one
+ # with debugging information.
+
+ if {(${lib1opts} == "" && ${lib2opts} != "" && ${lib1first} == 1)
+ || (${lib1opts} != "" && ${lib2opts} == "" && ${lib1first} == 0)} {
+ setup_kfail *-*-* gdb/1824
+ }
+
+ gdb_test "continue" "Breakpoint .* bar .*${expected_file}\\..*" \
+ "run to breakpoint - $testopts"
+}
+
+foreach lib1opts {{} {debug}} {
+ foreach lib2opts {{} {debug}} {
+ foreach lib1first {1 0} {
+ do_test $lib1opts $lib2opts $lib1first
+ }
+ }
+}
Index: testsuite/gdb.base/weaklib1.c
===================================================================
RCS file: testsuite/gdb.base/weaklib1.c
diff -N testsuite/gdb.base/weaklib1.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/weaklib1.c 30 Nov 2004 21:22:26 -0000
@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2004 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ USA. */
+
+void __attribute__((weak))
+bar (void)
+{
+ puts ("bar in u1");
+}
Index: testsuite/gdb.base/weaklib2.c
===================================================================
RCS file: testsuite/gdb.base/weaklib2.c
diff -N testsuite/gdb.base/weaklib2.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/weaklib2.c 30 Nov 2004 21:22:26 -0000
@@ -0,0 +1,31 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2004 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ USA. */
+
+void bar (void);
+void
+foo (void)
+{
+ bar ();
+}
+
+void
+bar (void)
+{
+ puts ("bar in u2");
+}
Index: testsuite/lib/gdb.exp
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/testsuite/lib/gdb.exp,v
retrieving revision 1.58
diff -u -p -r1.58 gdb.exp
--- testsuite/lib/gdb.exp 10 Sep 2004 01:04:59 -0000 1.58
+++ testsuite/lib/gdb.exp 30 Nov 2004 21:24:17 -0000
@@ -1324,6 +1324,30 @@ proc gdb_compile {source dest type optio
global gdb_wrapper_flags;
global gdb_wrapper_initialized;
+ # Add platform-specific options if a shared library was specified using
+ # "shlib=librarypath" in OPTIONS.
+ set new_options ""
+ set shlib_found 0
+ foreach opt $options {
+ if [regexp {^shlib=(.*)} $opt dummy_var shlib_name] {
+ lappend source $shlib_name
+ if {$shlib_found == 0} {
+ set shlib_found 1
+ global gcc_compiled
+ if { ($gcc_compiled
+ && ([istarget "powerpc*-*-aix*"]
+ || [istarget "rs6000*-*-aix*"] )) } {
+ lappend options "additional_flags=-L${objdir}/${subdir}"
+ } elseif { [istarget "mips-sgi-irix*"] } {
+ lappend options "additional_flags=-rpath ${objdir}/${subdir}"
+ }
+ }
+ } else {
+ lappend new_options $opt
+ }
+ }
+ set options $new_options
+
if [target_info exists gdb_stub] {
set options2 { "additional_flags=-Dusestubs" }
lappend options "libs=[target_info gdb_stub]";
@@ -1434,6 +1458,50 @@ proc gdb_compile_objc {source dest type
}
}
+# Build a shared library from SOURCES. You must use get_compiler_info
+# first.
+
+proc gdb_compile_shlib {sources dest options} {
+ global gcc_compiled
+
+ set obj_options $options
+ if {$gcc_compiled == 0} {
+ if [istarget "hppa*-hp-hpux*"] then {
+ lappend obj_options "additional_flags=+z"
+ } elseif { [istarget "mips-sgi-irix*"] } {
+ # Disable SGI compiler's implicit -Dsgi
+ lappend obj_options "additional_flags=-Usgi"
+ } else {
+ # don't know what the compiler is...
+ }
+ } else {
+ if { !([istarget "powerpc*-*-aix*"]
+ || [istarget "rs6000*-*-aix*"]) } {
+ lappend obj_options "additional_flags=-fpic"
+ }
+ }
+
+ set outdir [file dirname $dest]
+ set objects ""
+ foreach source $sources {
+ set sourcebase [file tail $source]
+ if {[gdb_compile $source "${outdir}/${sourcebase}.o" object $obj_options] != ""} {
+ return -1
+ }
+ lappend objects ${outdir}/${sourcebase}.o
+ }
+
+ if [istarget "hppa*-*-hpux*"] {
+ remote_exec build "ld -b ${objects} -o ${dest}"
+ } else {
+ set link_options options
+ lappend link_options "additional_flags=-shared"
+ if {[gdb_compile "${objects}" "${dest}" executable $link_options] != ""} {
+ return -1
+ }
+ }
+}
+
proc send_gdb { string } {
global suppress_flag;
if { $suppress_flag } {