[Bug c/71033] New: Segmentation fault c + intel assembly, unable to use EBX

["formateu at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71033

            Bug ID: 71033
           Summary: Segmentation fault c + intel assembly, unable to use
                    EBX
           Product: gcc
           Version: 6.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: formateu at gmail dot com
  Target Milestone: ---

Created attachment 38459
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38459&action=edit
the preprocessed file

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/6.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc-multilib/src/gcc/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --enable-multilib --disable-werror
--enable-checking=release
Thread model: posix
gcc version 6.1.1 20160501 (GCC) 


Program runs intel x86 assembly function in main. Use of the EBX register
inside that function causes segmentation fault (after return from function).
It seems like gcc is using EBX instead of EBP before function call.
Program compiled using clang works properly.
Bug was noticed firstly on gcc 5.3.0 version, but is still present on latest
repository version.

Used makefile:

CC=gcc
CFLAGS= -Wall -m32 -O0 -save-temps

all: main.o f.o
 $(CC) $(CFLAGS) main.o f.o -o fun

main.o: main.c
  $(CC) $(CFLAGS) -c main.c -o main.o


command : make && ./fun 2


f.o: f.s
  nasm -f elf -g f.s -o f.o

main.c :
#include "f.h" //only void f(char*)

int main(int argc, char *argv[])
{
  if(argc < 2) {
    return 1;
  }

  f(argv[1]);

  return 0;
}

f.s :
;f.i is not generated

  section .text
  global f
f:
  push ebp
  mov ebp, esp
  mov eax, [ebp+8]
  mov ebx, 9
begin:
  mov cl, [eax]
  cmp cl, 0 
  jz end
  add cl, 1
  mov [eax], cl
  inc eax
  jmp begin
end:
  mov esp, ebp
  pop ebp
  ret