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/libc/stdlib/Makefile.in b/libc/stdlib/Makefile.in
index 73e5462f6..9e96f03bb 100644
--- a/libc/stdlib/Makefile.in
+++ b/libc/stdlib/Makefile.in
@@ -27,6 +27,8 @@ CSRC-$(if $(findstring yy,$(UCLIBC_HAS_FLOATS)$(UCLIBC_SUSV3_LEGACY)),y) += \
 	gcvt.c
 CSRC-$(UCLIBC_SUSV3_LEGACY) += mktemp.c
 
+CFLAGS-abort.c = -fasynchronous-unwind-tables
+
 # multi source stdlib.c
 CSRC-y += abs.c labs.c atoi.c atol.c strtol.c strtoul.c _stdlib_strto_l.c \
 	qsort.c qsort_r.c bsearch.c \