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

[Simon Marchi <simark@simark.ca>]

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.

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

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon