Subject: bug#20614: Segmentation fault when building on Power8 Little Endian

From: Eli Zaretskii <[email-masked]>
Date: Fri, 02 Oct 2015 16:46:23 +0300

> Cc: [email-masked]
> From: Petr Hracek <[email-masked]>
> Date: Fri, 2 Oct 2015 14:58:56 +0200
> 
> On 10/02/2015 10:49 AM, Eli Zaretskii wrote:
> >> Cc: [email-masked]
> >> From: Petr Hracek <[email-masked]>
> >> Date: Fri, 2 Oct 2015 10:36:27 +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.