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Re: [PATCH][gdb, c++] Improve error message when using libstdcxx without SDT probes
- From: Tom de Vries <tdevries at suse dot de>
- To: Sergio Durigan Junior <sergiodj at redhat dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Mon, 26 Aug 2019 19:26:59 +0200
- Subject: Re: [PATCH][gdb, c++] Improve error message when using libstdcxx without SDT probes
- References: <20190725210447.GA26123@delia> <87h86410g2.fsf@redhat.com>
On 26-08-19 16:11, Sergio Durigan Junior wrote:
> On Thursday, July 25 2019, Tom de Vries wrote:
>
>> Hi,
>>
>> When using catch catch/rethrow/catch, a libstdcxx with SDT probes is required
>> for both the regexp argument, and the convenience variable $_exception (
>> https://sourceware.org/gdb/current/onlinedocs/gdb/Set-Catchpoints.html ).
>>
>> Currently, when using these features with a libstdcxx without SDT probes, we
>> get the cryptic error message:
>> ...
>> not stopped at a C++ exception catchpoint
>> ...
>>
>> Improve this by instead emitting the more helpful:
>> ...
>> did not find exception probe (does libstdcxx have SDT probes?)
>> ...
>>
>> Tested on x86_64-linux.
>>
>> OK for trunk?
>
> Thanks for the patch.
>
>> Thanks,
>> - Tom
>>
>> [gdb, c++] Improve error message when using libstdcxx without SDT probes
>>
>> gdb/ChangeLog:
>>
>> 2019-07-25 Tom de Vries <tdevries@suse.de>
>>
>> PR c++/24852
>> * break-catch-throw.c (fetch_probe_arguments): Improve error mesage
>> when pc_probe.prob == NULL.
>>
>> gdb/testsuite/ChangeLog:
>>
>> 2019-07-25 Tom de Vries <tdevries@suse.de>
>>
>> PR c++/24852
>> * gdb.cp/no-libstdcxx-probe.exp: New test.
>>
>> ---
>> gdb/break-catch-throw.c | 6 ++-
>> gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp | 58 +++++++++++++++++++++++++++++
>> 2 files changed, 62 insertions(+), 2 deletions(-)
>>
>> diff --git a/gdb/break-catch-throw.c b/gdb/break-catch-throw.c
>> index 0677a55ee5..2d91285312 100644
>> --- a/gdb/break-catch-throw.c
>> +++ b/gdb/break-catch-throw.c
>> @@ -106,8 +106,10 @@ fetch_probe_arguments (struct value **arg0, struct value **arg1)
>> unsigned n_args;
>>
>> pc_probe = find_probe_by_pc (pc);
>> - if (pc_probe.prob == NULL
>> - || pc_probe.prob->get_provider () != "libstdcxx"
>> + if (pc_probe.prob == NULL)
>> + error (_("did not find exception probe (does libstdcxx have SDT probes?)"));
>> +
>> + if (pc_probe.prob->get_provider () != "libstdcxx"
>> || (pc_probe.prob->get_name () != "catch"
>> && pc_probe.prob->get_name () != "throw"
>> && pc_probe.prob->get_name () != "rethrow"))
>> diff --git a/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp b/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp
>> new file mode 100644
>> index 0000000000..4c1a706ae0
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp
>> @@ -0,0 +1,58 @@
>> +# Copyright 2019 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 3 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, see <http://www.gnu.org/licenses/>.
>> +
>> +standard_testfile exceptprint.cc
>> +
>> +if {[skip_cplus_tests]} {
>> + return -1
>> +}
>> +
>> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
>> + return -1
>> +}
>> +
>> +if {![runto_main]} {
>> + return -1
>> +}
>> +
>> +set libstdcxx_probe_tests_supported [skip_libstdcxx_probe_tests]
>
> Not your fault, but this reversed logic (skip_libstdcxx_probe_tests
> returns 0 if the tests should be skipped) is kinda confusing.
>
[ FTR, dealt with here (
https://sourceware.org/ml/gdb-patches/2019-08/msg00595.html ). ]
>> +
>> +if { $libstdcxx_probe_tests_supported == 1 } {
>> + untested "Have libstdc++ stap probe"
>> + return -1
>> +}
>> +
>> +proc do_continue_to_catchpoint {name} {
>> + global gdb_prompt
>> +
>> + gdb_test_multiple "continue" $name {
>> + -re "Continuing.*Catchpoint \[0-9\].*\r\n$gdb_prompt $" {
>
> You can use $decimal instead of \[0-9\] if you want.
>
Done.
>> + pass $name
>> + }
>> + }
>> +}
>> +
>> +proc do_exceptprint_tests {prefix output} {
>> + with_test_prefix $prefix {
>> + do_continue_to_catchpoint "continue to throw"
>> + gdb_test "print \$_exception" \
>> + "did not find exception probe \\(does libstdcxx have SDT probes\\?\\).*"
>> + }
>> +}
>
> You don't seem to use $output here.
>
Hmm, and also prefix doesn't make much sense. In fact, the code becomes
more clear if I just inline the procs, and replace the gdb_test_multiple
with gdb_test.
>> +
>> +gdb_test "catch throw" "Catchpoint \[0-9\]+ \\(throw\\)" \
>> + "catch throw"
>
> $decimal if you want.
>
Done.
>> +
>> +do_exceptprint_tests string "$hex \"hi bob\""
>
> The patch looks good to me. Thanks for doing this.
Committed as below.
Thanks,
- Tom
[gdb, c++] Improve error message when using libstdcxx without SDT probes
When using catch catch/rethrow/catch, a libstdcxx with SDT probes is required
for both the regexp argument, and the convenience variable $_exception (
https://sourceware.org/gdb/current/onlinedocs/gdb/Set-Catchpoints.html ).
Currently, when using these features with a libstdcxx without SDT probes, we
get the cryptic error message:
...
not stopped at a C++ exception catchpoint
...
Improve this by instead emitting the more helpful:
...
did not find exception probe (does libstdcxx have SDT probes?)
...
Tested on x86_64-linux.
gdb/ChangeLog:
2019-07-25 Tom de Vries <tdevries@suse.de>
PR c++/24852
* break-catch-throw.c (fetch_probe_arguments): Improve error mesage
when pc_probe.prob == NULL.
gdb/testsuite/ChangeLog:
2019-07-25 Tom de Vries <tdevries@suse.de>
PR c++/24852
* gdb.cp/no-libstdcxx-probe.exp: New test.
---
gdb/break-catch-throw.c | 6 +++--
gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp | 41 +++++++++++++++++++++++++++++
2 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/gdb/break-catch-throw.c b/gdb/break-catch-throw.c
index 0677a55ee5..2d91285312 100644
--- a/gdb/break-catch-throw.c
+++ b/gdb/break-catch-throw.c
@@ -106,8 +106,10 @@ fetch_probe_arguments (struct value **arg0, struct value **arg1)
unsigned n_args;
pc_probe = find_probe_by_pc (pc);
- if (pc_probe.prob == NULL
- || pc_probe.prob->get_provider () != "libstdcxx"
+ if (pc_probe.prob == NULL)
+ error (_("did not find exception probe (does libstdcxx have SDT probes?)"));
+
+ if (pc_probe.prob->get_provider () != "libstdcxx"
|| (pc_probe.prob->get_name () != "catch"
&& pc_probe.prob->get_name () != "throw"
&& pc_probe.prob->get_name () != "rethrow"))
diff --git a/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp b/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp
new file mode 100644
index 0000000000..79826ea2d2
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/no-libstdcxx-probe.exp
@@ -0,0 +1,41 @@
+# Copyright 2019 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 3 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, see <http://www.gnu.org/licenses/>.
+
+standard_testfile exceptprint.cc
+
+if {[skip_cplus_tests]} {
+ return -1
+}
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
+ return -1
+}
+
+if {![runto_main]} {
+ return -1
+}
+
+if { [skip_libstdcxx_probe_tests] == 0 } {
+ untested "Have libstdc++ stap probe"
+ return -1
+}
+
+gdb_test "catch throw" "Catchpoint $decimal \\(throw\\)" \
+ "catch throw"
+
+gdb_test "continue" "Continuing.*Catchpoint $decimal.*"
+
+gdb_test "print \$_exception" \
+ "did not find exception probe \\(does libstdcxx have SDT probes\\?\\).*"