Re: [PATCH] Avoid crash in dwarf2/read.c:determine_prefix

[Tom Tromey <tromey@adacore.com>]

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

Simon> On 2026-04-23 14:52, Tom Tromey wrote:
>> I found a gdb crash when using some changes to gnat-llvm to have it
>> emit unqualified names in the DWARF.  The crash happens because
>> determine_prefix does this:
>> 
>> return dwarf2_full_name (nullptr, parent, cu);
>> 
>> However, dwarf2_full_name can return NULL, causing a crash in the
>> caller.
>> 
>> The particular DWARF causing this is pretty strange -- it is a
>> function nested inside another nameless function.  This may be a bug
>> in gnat-llvm, something I plan to investigate.
>> 
>> Meanwhile, gdb shouldn't crash.  This patch changes determine_prefix
>> to avoid possible crashes here, by following its contract and not
>> returning NULL.
>> 
>> I'm not sure if it's worthwhile to write a test case for this.

Simon> Seems fine.  Did you go around and check if other calls to
Simon> dwarf2_full_name handled nullptr correctly?  Most of them do, but others
Simon> seem like they would have a problem if dwarf2_full_name returned
Simon> nullptr.  Or perhaps if in some cases we can prove that dwarf2_full_name
Simon> can't return nullptr, then we could use a gdb_assert.

I didn't generally look.  Looking now though they generally seem fine.

Really what we should do is rewrite all the name computation code.  It's
overly convoluted and confusing, and the cooked indexer proved that a
lot of the hair isn't needed.

Tom