Fix "info break" + "catch catch" + -static-{libstdc++,libgcc}
If you debug current GDB, set a "catch catch/throw/rethrow"
catchpoint, and then do "info breakpoints", the top GDB hits an
internal error:
(top-gdb) catch catch
Catchpoint 1 (catch)
(top-gdb) info breakpoints
Num Type Disp Enb Address What
1 breakpoint keep y src/gdb/breakpoint.c:6040: internal-error: void print_one_breakpoint_location(breakpoint*, bp_location*, int, bp_location**, int): Assertion `b->loc == NULL || b->loc->next == NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n)
The assertion in question is asserting that a breakpoint with a
print_one method only has one location, and it fails because this
catchpoint ends up with two locations.
Internally, "catch catch" sets a breakpoint at __cxa_begin_catch. If
we do that manually, we see the locations:
(top-gdb) b -qualified __cxa_begin_catch
Breakpoint 2 at 0xb122b0 (2 locations)
(top-gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y <MULTIPLE>
2.1 y 0x0000000000b122b0 <__cxa_begin_catch>
2.2 y 0x00007ffff2f4ddb0 in __cxxabiv1::__cxa_begin_catch(void*) at ../../../../libstdc++-v3/libsupc++/eh_catch.cc:41
Note that I had used -qualified. It seems strange that we get a
location for a namespaced symbol, but that happens because the minimal
symbol for that address is indeed called __cxa_begin_catch.
The real issue is that gdb is linked with
-static-libgcc/-static-libstdc++. And then, it _also_ ends up with
shared libstc++ loaded:
(top-gdb) info sharedlibrary stdc++
From To Syms Read Shared Object Library
0x00007ffff2f4b380 0x00007ffff2ffc018 Yes /lib64/libstdc++.so.6
Location 2.2 is set within libstdc++.so.6's range:
(top-gdb) p 0x00007ffff2f4b380 <= 0x00007ffff2f4ddb0 && 0x00007ffff2f4ddb0 < 0x00007ffff2ffc018
$1 = true
So due to -static-lib*, we end up with _two_ copies of the
__cxa_begin_catch code:
(top-gdb) disassemble 0x0000000000b122b0
Dump of assembler code for function __cxa_begin_catch:
0x0000000000b122b0 <+0>: push %rbx
0x0000000000b122b1 <+1>: mov %rdi,%rbx
0x0000000000b122b4 <+4>: callq 0xb11a80 <__cxa_get_globals>
0x0000000000b122b9 <+9>: movabs $0xb8b1aabcbcd4d500,%rdx
...
(top-gdb) disassemble 0x00007ffff2f4ddb0
Dump of assembler code for function __cxxabiv1::__cxa_begin_catch(void*):
0x00007ffff2f4ddb0 <+0>: push %rbx
0x00007ffff2f4ddb1 <+1>: mov %rdi,%rbx
0x00007ffff2f4ddb4 <+4>: callq 0x7ffff2f4a090 <__cxa_get_globals@plt>
0x00007ffff2f4ddb9 <+9>: movabs $0xb8b1aabcbcd4d500,%rdx
...
I think we end up with libstdc++.so.6 loaded because
libsource-highlight.so depends on it.
Irrespective of whether it's a good idea to use
-static-libgcc/-static-libstdc++, GDB should not crash. Since there
are two copies of the code, it seems right to have more than one
location. So the fix is just to remove the assertion.
A testcase is included, which mimics the scenerio described above,
with binary linked with -static-lib{stdc++,gcc} and a shared library
that is linked normally, along with other combinations for good
measure.
gdb/ChangeLog:
2019-07-09 Pedro Alves <palves@redhat.com>
PR c++/15468
* breakpoint.c (print_one_breakpoint_location): Remove
single-location assert.
gdb/testsuite/ChangeLog:
2019-07-09 Pedro Alves <palves@redhat.com>
PR c++/15468
* gdb.cp/except-multi-location-lib.cc: New.
* gdb.cp/except-multi-location-main.cc: New.
* gdb.cp/except-multi-location.exp: New.
This commit is contained in:
Pedro Alves
parent
0826779b99
commit
b58a68fe57
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@ -1,3 +1,9 @@
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2019-07-09 Pedro Alves <palves@redhat.com>
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PR c++/15468
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* breakpoint.c (print_one_breakpoint_location): Remove
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single-location assert.
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2019-07-09 Tom Tromey <tom@tromey.com>
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* contrib/ari/gdb_ari.sh: Change common to gdbsupport.
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@ -6033,13 +6033,7 @@ print_one_breakpoint_location (struct breakpoint *b,
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/* 5 and 6 */
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if (b->ops != NULL && b->ops->print_one != NULL)
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{
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/* Although the print_one can possibly print all locations,
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calling it here is not likely to get any nice result. So,
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make sure there's just one location. */
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gdb_assert (b->loc == NULL || b->loc->next == NULL);
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b->ops->print_one (b, last_loc);
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}
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b->ops->print_one (b, last_loc);
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else
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switch (b->type)
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{
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@ -1,3 +1,10 @@
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2019-07-09 Pedro Alves <palves@redhat.com>
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PR c++/15468
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* gdb.cp/except-multi-location-lib.cc: New.
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* gdb.cp/except-multi-location-main.cc: New.
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* gdb.cp/except-multi-location.exp: New.
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2019-07-09 Sergio Durigan Junior <sergiodj@redhat.com>
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* gdb.base/printcmds.exp (test_printf_convenience_var): Set
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@ -0,0 +1,25 @@
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/* Copyright 2019 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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void
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trycatch_lib ()
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{
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try
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{
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throw 1;
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}
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catch (...)
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{
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}
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}
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@ -0,0 +1,36 @@
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/* Copyright 2019 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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extern void trycatch_lib ();
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void
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trycatch_main ()
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{
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try
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{
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throw 1;
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}
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catch (...)
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{
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}
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}
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int
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main ()
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{
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trycatch_lib ();
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trycatch_main ();
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return 0;
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}
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@ -0,0 +1,87 @@
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# Copyright 2019 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Regression test for a GDB internal error that would trigger if a
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# "catch catch" catchpoint ended up with multiple locations. This
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# testcase exercises that scenario by building the binary with
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# -static-libgcc/-static-libstdc++ and a shared library that depends
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# on the libstc++.so DSO (which is how GDB was built and revealed the
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# bug), and vice versa.
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if {[skip_shlib_tests]} {
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return 0
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}
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# STATIC_BIN indicates whether to build the main binary with
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# -static-libgcc/-static-libstdc++. STATIC_LIB is the same, but for
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# the shared library.
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proc test_multi_libstdcpp {static_bin static_lib} {
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global srcdir subdir
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global decimal hex
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# Library file.
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set libname "except-multi-location-lib"
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set srcfile_lib ${srcdir}/${subdir}/${libname}.cc
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set binfile_lib [standard_output_file ${libname}-$static_bin-$static_lib.so]
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set lib_flags {debug c++}
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if {$static_lib} {
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lappend lib_flags additional_flags=-static-libgcc additional_flags=-static-libstdc++
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}
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# Binary file.
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set testfile "except-multi-location-main"
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set srcfile ${srcdir}/${subdir}/${testfile}.cc
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set binfile [standard_output_file ${testfile}-$static_bin-$static_lib]
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set bin_flags [list debug c++ shlib=${binfile_lib}]
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if {$static_bin} {
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lappend bin_flags additional_flags=-static-libgcc additional_flags=-static-libstdc++
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}
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if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $lib_flags] != ""
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|| [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
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untested "failed to compile"
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return -1
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}
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clean_restart
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gdb_load ${binfile}
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gdb_load_shlib $binfile_lib
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if ![runto_main] {
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fail "can't run to main"
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return 0
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}
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gdb_test "catch catch" "Catchpoint \[0-9\]+ \\(catch\\)" \
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"catch catch"
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gdb_test "catch throw" "Catchpoint \[0-9\]+ \\(throw\\)" \
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"catch throw"
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gdb_test "catch rethrow" "Catchpoint \[0-9\]+ \\(rethrow\\)" \
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"catch rethrow"
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set ws "\[ \t\]*"
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gdb_test "info breakpoints" \
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[multi_line \
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"${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception catch" \
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"${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception throw" \
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"${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception rethrow"]
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}
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# Try different static/not-static combinations.
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foreach_with_prefix static_lib {"0" "1"} {
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foreach_with_prefix static_bin {"0" "1"} {
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test_multi_libstdcpp $static_lib $static_bin
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}
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}
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