immediate segmentation fault with LLVM/Clang 9

[David Demelier]

Hello,

I don't know where is the appropriate place to ask. I've upgraded my 
toolchain to LLVM 9 on my Clang based Linux distribution and everything 
built and ran fine except... busybox.

I suspect busybox is built with some incompatible flags because it 
immediately segfaults at startup of an applet (not all though). It works 
like a charm with gcc though.

Built with :

# make CC=clang HOSTCC=clang CROSS_COMPILE=llvm-

The .config is the default. I've only added CONFIG_DEBUG=y and 
CONFIG_STATIC=y. But applets crash even without those.

FWIW, the following warnings appear as well while building:

clang-9: warning: optimization flag '-finline-limit=0' is not supported 
[-Wignored-optimization-argument]
clang-9: warning: optimization flag '-falign-jumps=1' is not supported 
[-Wignored-optimization-argument]
clang-9: warning: optimization flag '-falign-labels=1' is not supported 
[-Wignored-optimization-argument]
clang-9: warning: optimization flag '-falign-loops=1' is not supported 
[-Wignored-optimization-argument]
clang-9: warning: argument unused during compilation: '-static-libgcc' 
[-Wunused-command-line-argument]

I can debug but without many useful information:

(gdb) run sh
Starting program: /src/vanilla/core/busybox/busybox-1.30.1/busybox sh

Program received signal SIGSEGV, Segmentation fault.
0x00000000002ced34 in ash_main (argc=1, argv=0x7fffffffec80) at 
shell/ash.c:14155
14155           INIT_G_misc();
(gdb) bt
#0  0x00000000002ced34 in ash_main (argc=1, argv=0x7fffffffec80) at 
shell/ash.c:14155
#1  0x000000000022e3ea in run_applet_no_and_exit (applet_no=289, 
name=<optimized out>, argv=0x7fffffffec80) at libbb/appletlib.c:996
#2  0x000000000022e9b5 in run_applet_and_exit (name=0x7fffffffee96 "sh", 
argv=0x7fffffffec80) at libbb/appletlib.c:1014
#3  0x000000000022ed51 in busybox_main (argv=0x7fffffffec80) at 
libbb/appletlib.c:957
#4  0x000000000022e9bd in run_applet_and_exit (name=0x7fffffffee8e 
"busybox", argv=0x7fffffffec78) at libbb/appletlib.c:1007
#5  0x000000000022e5cb in main (argc=<optimized out>, 
argv=0x7fffffffec78) at libbb/appletlib.c:1122

The trace is not meaningful though.

If I erase all CFLAGS using:

# make CC=clang HOSTCC=clang CROSS_COMPILE=llvm- CFLAGS=""

It works fine so I think there are too much options that are incompatible?

-- 
David