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/signal/Makefile.in b/libc/signal/Makefile.in
index a7e307871..ed8598b07 100644
--- a/libc/signal/Makefile.in
+++ b/libc/signal/Makefile.in
@@ -24,6 +24,8 @@ ifneq ($(strip $(ARCH_OBJS)),)
 CSRC-y := $(filter-out $(notdir $(ARCH_OBJS:.o=.c)),$(CSRC-y))
 endif
 
+CFLAGS-raise.c = -fasynchronous-unwind-tables
+
 SIGNAL_DIR := $(top_srcdir)libc/signal
 SIGNAL_OUT := $(top_builddir)libc/signal