[PATCH 1/1] dwarf_loader: Fix sorting of Rust structs

From: Arnaldo Carvalho de Melo
Date: Tue Feb 14 2023 - 16:13:59 EST


We may have structs with fields on the same offset, don't move anything
in that case, otherwise we get into an eternal loop, doh.

Tested with the Linux kernel built with CONFIG_RUST + all the code
examples, first Rust struct where this happened was:

(gdb) p type->namespace.name
$2 = 0x7fffda938497 "((), char)"
(gdb) p type->nr_members
$3 = 2
(gdb) p current_member->name
$4 = 0x7fffda918f36 "__1"
(gdb) p next_member->name
$5 = 0x7fffda91765c "__0"
(gdb) p current_member->byte_offset
$6 = 0
(gdb) p next_member->byte_offset
$7 = 0

But this shows that --lang_exclude should be better positioned as we're
now needlessly loading all the tags for Rust DWARF to then just trow it
away at the cu__filter() in pahole :-\

Too late in the 1.25 release cycle for that, optimize it in 1.26.

Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
dwarf_loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dwarf_loader.c b/dwarf_loader.c
index a77598dc3affca88..acdb68d5dd33f148 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -2857,7 +2857,7 @@ restart:

struct class_member *next_member = list_entry(current_member->tag.node.next, typeof(*current_member), tag.node);

- if (current_member->byte_offset < next_member->byte_offset)
+ if (current_member->byte_offset <= next_member->byte_offset)
continue;

list_del(&current_member->tag.node);
--
2.39.1