Issue with gdb and urls
Camille Lamy
Julien Brianceau (jbriance)
Hi,
I don’t know what changed, but you might workaround this by using the c_str() method.
For instance :
$ gdb --args url_unittests --single-process-tests --gtest_filter=GURLTest.Components
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Reading symbols from ../build-master-dbg/url_unittests...done.
(gdb) b GURL::spec
Breakpoint 1 at 0x7148c6: file ../src/url/gurl.cc, line 207.
(gdb) r
Starting program: /var/local/jbriance/host-chromium/build-master-dbg/url_unittests --single-process-tests --gtest_filter=GURLTest.Components
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Debugger detected, switching to single process mode.
Pass --test-launcher-debug-launcher to debug the launcher itself.
Detected presence of a debugger, running without test timeouts.
Note: Google Test filter = GURLTest.Components
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from GURLTest
[ RUN ] GURLTest.Components
Breakpoint 1, GURL::spec (this=0x7fffffffd5f0) at ../src/url/gurl.cc:207
207 if (is_valid_ || spec_.empty())
(gdb) print spec_
$1 = <incomplete type>
(gdb) print spec_.c_str()
$2 = (const std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::value_type *) 0xd0856e4eea0 "http://user:pa...@google.com:99/foo;bar?q=a#ref"
(gdb)
I hope this is what you were looking for :)
Julien
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Arthur Hemery
I very often get hangs that requires SIGKILLing gdb when using such methods, as below for a GURL example :
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Julien Brianceau (jbriance)
Hi,
No, I’ve no idea why this hangs, but to be honest it is also quite slow for me to show the result of c_str() : around 5 seconds and I’m running gdb on a huge compilation server.
Another workaround which is quick & dirty, but should help avoiding the hang issue you face :
Breakpoint 1, GURL::spec (this=0x7fffffffd5f0) at ../src/url/gurl.cc:207
207 if (is_valid_ || spec_.empty())
(gdb) print spec_
$1 = <incomplete type>
(gdb) p *(char**) ((int*) &spec_+4)
$2 = 0x91236c98ea0 "http://user:pa...@google.com:99/foo;bar?q=a#ref"
Please note that the +4 that I use here depends on your architecture and toolchain, so you might have to test other values to find the right one for you.
Julien
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Julien Brianceau (jbriance)
Hi again,
After looking a bit more into this, this seems to be related to inlined namespace.
Here’s something that works for me :
207 if (is_valid_ || spec_.empty())
(gdb) p spec_
$1 = <incomplete type>
(gdb) ptype std::__1::string
type = class std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > {
<incomplete type>
}
(gdb) p spec_
$2 = {<std::__1::__basic_string_common<true>> = {<No data fields>},
__r_ = {<std::__1::__compressed_pair_elem<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__rep, 0, false>> = {__value_ = {{__l = {__cap_ = 65, __size_ = 46,
__data_ = 0x3a03ecf19ea0 "http://user:pa...@google.com:99/foo;bar?q=a#ref"}, __s = {{__size_ = 65 'A', __lx = 65 'A'},
__data_ = "\000\000\000\000\000\000\000.\000\000\000\000\000\000\000\240\236\361\354\003:\000"}, __r = {__words = {65, 46,
63788534570656}}}}}, <std::__1::__compressed_pair_elem<std::__1::allocator<char>, 1, true>> = {<std::__1::allocator<char>> = {<No data fields>}, <No data fields>}, <No data fields>},
static npos = 18446744073709551615}
(gdb)
Julien
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Julien Brianceau (jbriance)
Hi again,
Adding the following GN arg solves the issue in my env :
use_custom_libcxx = false
When building url_unittests with this arg, I now have :
$ gdb --args url_unittests --single-process-tests --gtest_filter=GURLTest.Components
[...]
(gdb) b GURL::spec
Breakpoint 1 at 0x57ae96: file ../src/url/gurl.cc, line 207.
(gdb) r
[...]
Breakpoint 1, GURL::spec (this=0x7fffffffd870) at ../src/url/gurl.cc:207
207 if (is_valid_ || spec_.empty())
(gdb) p spec_
$1 = "http://user:pa...@google.com:99/foo;bar?q=a#ref"
(gdb)
So to me, the issue is coming from a mixup between libstdc++ and libc++, but I’m not familiar enough with those to be able to fully understand the problem.
According to git log, thomasanderson@ and thakis@ recently pushed changes about this GN arg. Maybe you can ask them if they have more insight into this,
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Nico Weber
Hi again,
Adding the following GN arg solves the issue in my env :
use_custom_libcxx = false
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