Cc: 20614@debbugs.gnu.org
From: Petr Hracek <phracek@redhat.com>
Date: Mon, 5 Oct 2015 09:40:15 +0200
What does this GDB command display in frame #1:
(gdb) p old_section_names + NEW_SECTION_H (nn).sh_name
?
It is a really strange.
in our unexelf.c is NEW_SECTION_H defined as
#define NEW_SECTION_H(n) \
(*(ElfW (Shdr) *) ((byte *) new_section_h + new_file_h->e_shentsize * (n)))
Paul Eggert did a some patch 1 or 2 year ago and modify it to
#define NEW_SECTION_H(n) \
(*(ElfW (Shdr) *) entry_address (new_section_h, n,
new_file_h->e_shentsize))
(gdb) frame 1
#1 0x00000000102e3724 in unexec (new_name=0x116387e8
"/home/phracek/rpmbuild/BUILD/emacs-24.3/src/emacs", old_name=0x11638838
"/home/phracek/rpmbuild/BUILD/emacs-24.3/src/temacs")
at unexelf.c:1258
1258 if (!strcmp (old_section_names + NEW_SECTION_H (nn).sh_name, ".data")
(gdb) p old_section_names
$1 = 0x3fffab1dbfcc ""
(gdb) p old_section_names + NEW_SECTION_H (nn).sh_name
No symbol "NEW_SECTION_H" in current context.
Use the expansion of that macro instead to display the value.
How to use the expansion.
Just type it by hand:
(gdb) p old_section_names + (*(ElfW (Shdr) *) ((byte *) new_section_h +
new_file_h->e_shentsize * (nn)))
Are you connected on freenode #emacs.
No.
First of all thank you for your time.
Well,
(gdb) p (*(ElfW (Shdr) *) ((byte *) new_section_h +
new_file_h->e_shentsize * (nn)))
No symbol "ElfW" in current context.
(gdb)
Also ElfBitsW does not exists.
(gdb) p ElfBitsW
No symbol "ElfBitsW" in current context.
(gdb)
You need to expand all these macros by hand. They are defined at the
beginning of unexelf.c:
#ifndef ElfW
# define ElfBitsW(bits, type) Elf##bits##_##type
# ifndef ELFSIZE
# ifdef _LP64
# define ELFSIZE 64
# else
# define ELFSIZE 32
# endif
# endif
/* This macro expands `bits' before invoking ElfBitsW. */
# define ElfExpandBitsW(bits, type) ElfBitsW (bits, type)
# define ElfW(type) ElfExpandBitsW (ELFSIZE, type)
#endif
I would suggest at first to rebuild Emacs with "-gdwarf-4 -g3"
compiler switches, maybe that will allow you to type expressions with
macros, and let GDB expand them using the debug info. Maybe.