bug#17806: 24.4.50; Branch emacs-24 fails to beuild on Debian

[Paul Eggert]

Eli Zaretskii wrote:
> Does "info source" work for you in such programs?

Yes and no.  It reports some information, but preprocessor macros are 
lost so it's not as good as when compiling without LTO.  For example:

(gdb) b emacs_open
Breakpoint 3 at 0x490330: file sysdep.c, line 2143.
(gdb) r
Starting program: 
/home/eggert/src/gnu/emacs/emacs-24-sc/src/bootstrap-emacs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7fffe1260700 (LWP 2323)]

Breakpoint 3, emacs_open (
    file=0x1333ea8 "/usr/local/share/emacs/24.3.91/site-lisp/subdirs.el",
    oflags=oflags@entry=0, mode=mode@entry=0) at sysdep.c:2143
(gdb) info source
Current source file is sysdep.c
Compilation directory is /home/eggert/src/gnu/emacs/emacs-24-sc/src
Located in /home/eggert/src/gnu/emacs/emacs-24-sc/src/sysdep.c
Contains 3445 lines.
Source language is c.
Compiled with (null) debugging format.
Does not include preprocessor macro info.
(gdb) p O_CLOEXEC
No symbol "O_CLOEXEC" in current context.