Re: [PATCH] [gdb/testsuite] Drop -nostdlib in gdb.dwarf2/typeddwarf.exp

[Tom de Vries <tdevries@suse.de>]

On 7/24/23 18:21, Simon Marchi wrote:
> On 7/13/23 10:15, Tom de Vries via Gdb-patches wrote:
>> As reported in PR testsuite/30633, when running test-case
>> gdb.dwarf2/typeddwarf.exp with target board native-gdbserver on Ubuntu
>> 22.04.2, we run into:
>> ...
>> (gdb) continue^M
>> Continuing.^M
>> ^M
>> Program received signal SIGSEGV, Segmentation fault.^M
>> 0x0000000000000001 in ?? ()^M
>> (gdb) FAIL: gdb.dwarf2/typeddwarf.exp: runto: run to main
>> ...
>>
>> We run into the FAIL as follows:
>> - due to using gdbserver, we attach at the point of the first instruction, in
>>    _start
>> - we then set a breakpoint at main
>> - the test-case is a .s file, that has main renamed to _start in the assembly,
>>    but not in the debuginfo
>> - setting a breakpoint at main sets the breakpoint at the same instruction
>>    we're currently stopped at
>> - continue doesn't hit the breakpoint, and we return out of _start, which
>>    causes a sigsegv
>>
>> Note that this is for the amd64 case (using gdb.dwarf2/typeddwarf-amd64.S).
>> For the i386 case (using gdb.dwarf2/typeddwarf.S), setting a breakpoint in
>> main sets it one insn after function entry, and consequently the problem does
>> not occur.
>>
>> The FAIL is a regression since commit 90cce6c0551 ("[gdb/testsuite] Add nopie
>> in a few test-cases").
>>
>> Without nopie the executable is PIE, with nopie it's static instead.
>>
>> In the PIE case, we attach at the point of _start in the dynamic linker, and
>> consequently we do not skip the breakpoint in main, and also don't run into
>> the FAIL.
>>
>> Fix this by:
>> - removing the -nostdlib setting, and
>> - renaming _start to main in both .S files.
>>
>> The change to use -nostdlib and rename main to _start was originally added
>> in commit 6edba76fe8b (submitted here:
>> https://sourceware.org/pipermail/gdb-patches/2011-May/082657.html ) , I assume
>> to fix the problem now fixed by using nopie.
>>
>> Tested on x86_64-linux.
>>
>> Reported-By: Simon Marchi <simon.marchi@efficios.com>
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30633
> 
> I have not dug in the code at all, but I confirm that the patch fixes
> the test.  Therefore:
> 
> Tested-By: Simon Marchi <simon.marchi@efficios.com>

Thanks for testing, committed.

- Tom