Re: [PATCH 1/4] [gdb/symtab] Fix htab_find_slot call in read_call_site_scope

Simon Marchi via Gdb-patches
2021-10-01T13:10:33Z

On 2021-10-01 08:33, Tom de Vries via Gdb-patches wrote:
> From: Simon Marchi <simon.marchi@polymtl.ca>
>
> In read_call_site_scope we have:
> ...
> call_site_local.pc = pc;
> slot = htab_find_slot (cu->call_site_htab, &call_site_local, INSERT);
> ...
>
> The call passes a call_site pointer as element. OTOH, the hashtab is created
> using hash_f == core_addr_hash and eq_f == core_addr_eq, so the element
> will be accessed through a CORE_ADDR pointer.
>
> This is not wrong (at least in C), given that pc is the first field in
> call_site.
>
> Nevertheless, as in call_site_for_pc, make the htab_find_slot call match the
> used hash_f and eq_f by using &pc instead:
> ...
> slot = htab_find_slot (cu->call_site_htab, &pc, INSERT);
> ...
>
> Tested on x86_64-linux.
>
> Co-Authored-By: Tom de Vries <tdevries@suse.de>
> ---
> gdb/dwarf2/read.c | 5 ++---
> gdb/gdbtypes.h | 4 +---
> 2 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 00aa64dd0ab..23870c04e74 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -13341,7 +13341,7 @@ read_call_site_scope (struct die_info *die, struct dwarf2_cu *cu)
> struct gdbarch *gdbarch = objfile->arch ();
> CORE_ADDR pc, baseaddr;
> struct attribute *attr;
> - struct call_site *call_site, call_site_local;
> + struct call_site *call_site;
> void **slot;
> int nparams;
> struct die_info *child_die;
> @@ -13369,8 +13369,7 @@ read_call_site_scope (struct die_info *die, struct dwarf2_cu *cu)
> cu->call_site_htab = htab_create_alloc_ex (16, core_addr_hash, core_addr_eq,
> NULL, &objfile->objfile_obstack,
> hashtab_obstack_allocate, NULL);
> - call_site_local.pc = pc;
> - slot = htab_find_slot (cu->call_site_htab, &call_site_local, INSERT);
> + slot = htab_find_slot (cu->call_site_htab, &pc, INSERT);
> if (*slot != NULL)
> {
> complaint (_("Duplicate PC %s for DW_TAG_call_site "
> diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
> index 2a641122aec..84b751e82e3 100644
> --- a/gdb/gdbtypes.h
> +++ b/gdb/gdbtypes.h
> @@ -1783,9 +1783,7 @@ struct call_site_parameter
>
> struct call_site
> {
> - /* * Address of the first instruction after this call. It must be
> - the first field as we overload core_addr_hash and core_addr_eq
> - for it. */

Ah, I had not seen this comment. So it was on purpose. Still, I think
that it makes it more confusing than anything. The patch LGTM.

Simon