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

[Simon Marchi <simark@simark.ca>]

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,

Simon