jmp label(,%eax,4) bug

[Alan Modra]

On Fri, 14 Jan 2000 rob@icell.hu wrote:

> The problem is in the assembler:
> When I replace the 3 occurances of a
> 	jmp	a_Label(,%eax,4)
> with
> 	push	Label(,%eax,4)
> 	ret
> , everything is going fine.

This bug report should really have been sent to bug-gnu-utils@gnu.org, or
to binutils@sourceware.cygnus.com, but since it came here I'll annoy the
gcc list with a reply too :-)

>From your list of packages, it seems that the assembler version causing
problems was binutils-2.9.5.0.22, while binutils-2.9.1.0.25 was OK.  This
is probably due to a bug I've only recently fixed.

Try the following with your assembler.
$ cat > z.s
 jmp 2(,%eax,4)
$ as z.s
$ objdump -dr a.out 

a.out:     file format elf32-i386

Disassembly of section .text:

00000000 <.text>:
   0:   ff 2c 85 02 00 00 00    ljmp   *0x2(,%eax,4)

Notice how the jmp has incorrectly turned into a ljmp.

The latest assembler (see http://sourceware.cygnus.com/binutils/ for info
on how to get a copy of the source) gives:

$ /usr/tmp/gas/gas/as-new z.s
z.s: Assembler messages:
z.s:1: Warning: Indirect jmp without `*'
$ objdump -dr a.out 

a.out:     file format elf32-i386

Disassembly of section .text:

00000000 <.text>:
   0:   ff 24 85 02 00 00 00    jmp    *0x2(,%eax,4)