libc: allow to backtrace out of abort call

Build raise and abort function with dwarf2 info by using
-fasynchronous-unwind-tables to make backtrace() working across a
call to abort.

A scenario where it could be useful is within a signal handler that
wants to dump a backtrace when catching some signal (i.e SIGABRT).
Without having abort & raise built with DWARF2 information, it is not
possible for the libgcc stack unwinder to walk through the call stack
out of the abort/raise function.

Impacts in terms of size are really limited

Current
   text    data     bss     dec     hex filename
    164       0       0     164      a4 ./libpthread/nptl/sysdeps/unix/sysv/linux/raise.os
    164       0       0     164      a4 ./libpthread/nptl/sysdeps/unix/sysv/linux/raise.oS
    220      24       4     248      f8 ./libc/stdlib/abort.os

With (-fasynchronous-unwind-tables)

   text    data     bss     dec     hex filename
    216       0       0     216      d8 ./libpthread/nptl/sysdeps/unix/sysv/linux/raise.os
    216       0       0     216      d8 ./libpthread/nptl/sysdeps/unix/sysv/linux/raise.oS
    280      24       4     308     134 ./libc/stdlib/abort.os

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>
Acked-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/libpthread/nptl/sysdeps/unix/sysv/linux/Makefile.commonarch b/libpthread/nptl/sysdeps/unix/sysv/linux/Makefile.commonarch
index e28cec247..b32bc9b5e 100644
--- a/libpthread/nptl/sysdeps/unix/sysv/linux/Makefile.commonarch
+++ b/libpthread/nptl/sysdeps/unix/sysv/linux/Makefile.commonarch
@@ -128,6 +128,8 @@ CFLAGS-timer_gettime.c = -I$(top_srcdir)librt -DIS_IN_librt
 CFLAGS-timer_routines.c = -I$(top_srcdir)librt -DIS_IN_librt
 CFLAGS-timer_settime.c = -I$(top_srcdir)librt -DIS_IN_librt
 
+CFLAGS-raise.c = -fasynchronous-unwind-tables
+
 CFLAGS-linux = -DNOT_IN_libc -DIS_IN_libpthread $(SSP_ALL_CFLAGS)
 
 CFLAGS-OMIT-libc_pthread_init.c = -DNOT_IN_libc -DIS_IN_libpthread