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Re: [patch] stabs assertion failure symbol_get_demangled_name
- From: Pedro Alves <pedro at codesourcery dot com>
- To: gdb-patches at sourceware dot org
- Cc: sami wagiaalla <swagiaal at redhat dot com>
- Date: Tue, 3 Aug 2010 17:58:54 +0100
- Subject: Re: [patch] stabs assertion failure symbol_get_demangled_name
- References: <4C509011.2040207@redhat.com>
On Wednesday 28 July 2010 21:16:17, sami wagiaalla wrote:
> Pedro reported a crash of code compiled with stabs on
>
> gdb_assert(gsymbol->language_specific.cplus_specific != NULL);
>
> in symbol_get_demangled_name. The problem was that
> stabsread.c:define_symbol was calling cp_scan_for_anonymous_namespaces
> before setting the name.
> I corrected that but there other case, and for
> those I changed the assertion into an if statement that returns null
> since symbol_natural_name depends on symbol_get_demangled_name to return
> null in order to fall back to gsymbol->name.
I tried this myself to check what symbol this was, and why doesn't this
assert trigger with dwarf. It's a typedef symbol. The dwarf reader
ends up with a call to symbol_set_demangled_name with a NULL name,
while the stabs reader never calls it, and, symbol_set_demangled_name with
a NULL name always allocates gsymbol->language_specific.cplus_specific even
in that case.
void
symbol_set_demangled_name (struct general_symbol_info *gsymbol,
char *name,
struct objfile *objfile)
{
if (gsymbol->language == language_cplus)
{
if (gsymbol->language_specific.cplus_specific == NULL)
symbol_init_cplus_specific (gsymbol, objfile);
gsymbol->language_specific.cplus_specific->demangled_name = name;
}
else
gsymbol->language_specific.mangled_lang.demangled_name = name;
}
I guess we could avoid a number of allocations if when
(gsymbol->language_specific.cplus_specific == NULL && name == NULL)
is true, we didn't allocate the cplus_specific bit.
> 2010-07-28 Sami Wagiaalla <swagiaal@redhat.com>
>
> * symtab.c (symbol_get_demangled_name): Remove assertion and
> return NULL when language_specific.cplus_specific is not initialized.
> * stabsread.c (define_symbol): Set the name before calling
> cp_scan_for_anonymous_namespaces.
Okay, thanks. Small formatting issue pointed out below.
> --- a/gdb/symtab.c
> +++ b/gdb/symtab.c
> @@ -381,10 +381,10 @@ char *
> symbol_get_demangled_name (const struct general_symbol_info *gsymbol)
> {
> if (gsymbol->language == language_cplus)
> - {
> - gdb_assert (gsymbol->language_specific.cplus_specific != NULL);
> + if (gsymbol->language_specific.cplus_specific != NULL)
> return gsymbol->language_specific.cplus_specific->demangled_name;
> - }
> + else
> + return NULL;
> else
> return gsymbol->language_specific.mangled_lang.demangled_name;
> }
In cases like this (if as only statement of if), it's preferred to
leave the outer {}'s in place, to future proof against dangling
else problems:
if (gsymbol->language == language_cplus)
{
if (gsymbol->language_specific.cplus_specific != NULL)
return gsymbol->language_specific.cplus_specific->demangled_name;
else
return NULL;
}
else
return gsymbol->language_specific.mangled_lang.demangled_name;
--
Pedro Alves