[PATCH] [gdb/symtab] Don't deduplicate variables in gdb-index

Tom de Vries via Gdb-patches
2023-08-04T17:36:24Z

When running test-case gdb.python/py-symbol.exp with target board
cc-with-gdb-index, we run into:
...
(gdb) python print (len (gdb.lookup_static_symbols ('rr')))^M
1^M
(gdb) FAIL: gdb.python/py-symbol.exp: print (len (gdb.lookup_static_symbols ('rr')))
...

[ Note that the test-case contains rr in both py-symtab.c:
...
static int __attribute__ ((used)) rr = 42; /* line of rr */
...
and py-symtab-2.c:
...
static int __attribute__ ((used)) rr = 99; /* line of other rr */
... ]

This passes with gdb-12-branch, and fails with gdb-13-branch.

AFAIU the current code in symtab_index_entry::minimize makes the assumption
that it's fine to store only one copy of rr in the gdb-index, because
"print rr" will only ever print one, and always the same.

But that fails to recognize that gdb supports gdb.lookup_static_symbols, which
returns a list of variables rather than the first one.

In other words, the current approach break feature parity between cooked index
and gdb-index.

Note btw that also debug-names has both instances:
...
[ 5] #00597969 rr:
<4> DW_TAG_variable DW_IDX_compile_unit=3 DW_IDX_GNU_internal=1
<4> DW_TAG_variable DW_IDX_compile_unit=4 DW_IDX_GNU_internal=1
...

Fix this in symtab_index_entry::minimize, by not deduplicating variables.

Tested on x86_64-linux, with target boards unix and cc-with-gdb-index.

PR symtab/30720
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30720
---
gdb/dwarf2/index-write.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index 66c5378d677..c3bc537521e 100644
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -294,7 +294,7 @@ symtab_index_entry::minimize ()
auto from = std::unique (cu_indices.begin (), cu_indices.end ());
cu_indices.erase (from, cu_indices.end ());

- /* We don't want to enter a variable or type more than once, so
+ /* We don't want to enter a variable more than once, so
remove any such duplicates from the list as well. When doing
this, we want to keep the entry from the first CU -- but this is
implicit due to the sort. This choice is done because it's
@@ -304,8 +304,7 @@ symtab_index_entry::minimize ()
[&] (offset_type val)
{
gdb_index_symbol_kind kind = GDB_INDEX_SYMBOL_KIND_VALUE (val);
- if (kind != GDB_INDEX_SYMBOL_KIND_TYPE
- && kind != GDB_INDEX_SYMBOL_KIND_VARIABLE)
+ if (kind != GDB_INDEX_SYMBOL_KIND_TYPE)
return false;

val &= ~GDB_INDEX_CU_MASK;

base-commit: 0133072f87b7ac0791413870876a0769ca7d44e0
--
2.35.3