https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117320
Bug ID: 117320
Summary: wrong debug info for function with cold alternative
(-g -O2)
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: eggert at cs dot ucla.edu
Target Milestone: ---
Created attachment 59464
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59464&action=edit
wrong debug info for backtrace_function with gcc -g -O2 x86-64
We ran into a problem when debugging GNU Emacs and I reproduced it with gcc
(GCC) 14.2.1 20240912 (Red Hat 14.2.1-3) on x86-64.
Decompress and compile the attached file eval.i.gz and check the results with:
gzip -d eval.i.gz
gcc -g -O2 -c eval.i
nm eval.o | grep -E 'backtrace_(next|function)'
gdb -ex 'print backtrace_next' -ex 'print backtrace_function' eval.o
nm outputs:
0000000000000bf0 T backtrace_function
00000000000002c8 t backtrace_function.cold
00000000000001bf t backtrace_function.part.0
0000000000000c90 T backtrace_next
However, gdb outputs:
$1 = {union specbinding *(union specbinding *)} 0xc90 <backtrace_next>
$2 = {Lisp_Object (union specbinding *)} 0xa369 <backtrace_function>
Although gdb reports the correct address for backtrace_next, it reports the
wrong address for backtrace_function.
The problem appears to occur because backtrace_function is optimized into cold
and hot parts, in different sections, and GCC outputs incorrect debug info in
this case.
