* [PATCH] [gdb/symtab] Remove superfluous handling of Ada main in write_cooked_index
@ 2023-08-03 13:34 Tom de Vries
2023-08-03 15:11 ` Tom Tromey
0 siblings, 1 reply; 2+ messages in thread
From: Tom de Vries @ 2023-08-03 13:34 UTC (permalink / raw)
To: gdb-patches; +Cc: Tom Tromey
I filed PR29179 about the following FAIL in test-case
gdb.ada/O2_float_param.exp with target board cc-with-gdb-index:
...
(gdb) break increment^M
Function "increment" not defined.^M
Make breakpoint pending on future shared library load? (y or [n]) n^M
(gdb) FAIL: gdb.ada/O2_float_param.exp: scenario=all: gdb_breakpoint: \
set breakpoint at increment
...
The FAIL was a regression since commit 2cf349be0e3 ("Do not put linkage names
into .gdb_index").
Before that commit we had:
...
$ readelf -w foo > READELF
$ grep callee.*increment READELF
[1568] callee__increment: 5 [global, function]
[3115] callee.increment: 5 [global, function]
...
but after only:
...
$ grep callee.*increment READELF
[3115] callee.increment: 5 [global, function]
...
The regression was fixed by commit 67e83a0deef ("Fix regression in
c-linkage-name.exp with gdb index"), which got us again:
...
$ grep callee.*increment READELF
[1568] callee__increment: 5 [global, function]
[3115] callee.increment: 5 [global, function]
...
The commit however did not claim that particular PR. A subsequent commit,
commit 5fea9794325 ("Improve Ada support in .gdb_index") did claim to fix it,
together with commit dd05fc7071a ("Change .gdb_index de-duplication
implementation").
The commit 5fea9794325 contained the following addition in write_cooked_index:
...
+ if (entry->per_cu->lang () == language_ada)
+ {
+ /* We want to ensure that the Ada main function's name
+ appears verbatim in the index. However, this name will
+ be of the form "_ada_mumble", and will be rewritten by
+ ada_decode. So, recognize it specially here and add it
+ to the index by hand. */
+ if (entry->tag == DW_TAG_subprogram
+ && strcmp (main_for_ada, name) == 0)
+ {
+ /* Leave it alone. */
+ }
+ else
+ {
+ /* In order for the index to work when read back into
+ gdb, it has to use the encoded name, with any
+ suffixes stripped. */
+ std::string encoded = ada_encode (name, false);
+ name = obstack_strdup (&symtab->m_string_obstack,
+ encoded.c_str ());
+ }
+ }
...
The code contains some special handling related to the Ada main function, so
let's look at that one: foo. Before commit 67e83a0deef we have:
...
$ grep foo.*function READELF
[3733] foo: 7 [global, function]
...
and after:
...
$ grep foo.*function READELF
[2738] _ada_foo: 7 [global, function]
[3733] foo: 7 [global, function]
...
so that looks identical to the callee.increment case.
At commit 5fea9794325, we have slightly different index numbers:
...
$ grep foo.*function READELF
[1658] foo: 7 [global, function]
[2738] _ada_foo: 7 [global, function]
...
but otherwise the same result.
If we disable the special handling of the Ada main function like so:
...
- if (entry->tag == DW_TAG_subprogram
+ if (false && entry->tag == DW_TAG_subprogram
...
we still have the exact same result because:
...
(gdb) p main_for_ada
$1 = 0x352e6a0 "_ada_foo"
...
and ada_encode ("_ada_foo", false) == "_ada_foo".
The comment seems to be copied from debug_names::insert, which does indeed use
ada_decode, while the code in write_cooked_index uses ada_encode instead.
Remove the superfluous special handling of Ada main in write_cooked_index.
Tested on x86_64-linux, with target boards unix and cc-with-gdb-index.
---
gdb/dwarf2/index-write.c | 27 ++++++---------------------
1 file changed, 6 insertions(+), 21 deletions(-)
diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index 62c2cc6ac7d..66c5378d677 100644
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -1128,8 +1128,6 @@ write_cooked_index (cooked_index *table,
const cu_index_map &cu_index_htab,
struct mapped_symtab *symtab)
{
- const char *main_for_ada = main_name ();
-
for (const cooked_index_entry *entry : table->all_entries ())
{
const auto it = cu_index_htab.find (entry->per_cu);
@@ -1139,25 +1137,12 @@ write_cooked_index (cooked_index *table,
if (entry->per_cu->lang () == language_ada)
{
- /* We want to ensure that the Ada main function's name
- appears verbatim in the index. However, this name will
- be of the form "_ada_mumble", and will be rewritten by
- ada_decode. So, recognize it specially here and add it
- to the index by hand. */
- if (entry->tag == DW_TAG_subprogram
- && strcmp (main_for_ada, name) == 0)
- {
- /* Leave it alone. */
- }
- else
- {
- /* In order for the index to work when read back into
- gdb, it has to use the encoded name, with any
- suffixes stripped. */
- std::string encoded = ada_encode (name, false);
- name = obstack_strdup (&symtab->m_string_obstack,
- encoded.c_str ());
- }
+ /* In order for the index to work when read back into
+ gdb, it has to use the encoded name, with any
+ suffixes stripped. */
+ std::string encoded = ada_encode (name, false);
+ name = obstack_strdup (&symtab->m_string_obstack,
+ encoded.c_str ());
}
else if (entry->per_cu->lang () == language_cplus
&& (entry->flags & IS_LINKAGE) != 0)
base-commit: 1720b64f735ff2798ab50ea9e2a40ab42af6cc6e
--
2.35.3
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] [gdb/symtab] Remove superfluous handling of Ada main in write_cooked_index
2023-08-03 13:34 [PATCH] [gdb/symtab] Remove superfluous handling of Ada main in write_cooked_index Tom de Vries
@ 2023-08-03 15:11 ` Tom Tromey
0 siblings, 0 replies; 2+ messages in thread
From: Tom Tromey @ 2023-08-03 15:11 UTC (permalink / raw)
To: Tom de Vries via Gdb-patches; +Cc: Tom de Vries, Tom Tromey
>>>>> "Tom" == Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:
[...great analysis...]
Tom> Remove the superfluous special handling of Ada main in write_cooked_index.
Thank you for doing this.
Approved-By: Tom Tromey <tom@tromey.com>
Tom
^ permalink raw reply [flat|nested] 2+ messages in thread
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