------- Comment #14 from ubizjak at gmail dot com 2009-03-01 20:13 -------
(In reply to comment #5)
> Uros, looking at this again, after manually changing
> leal $_48(,%eax,4), %eax
> to
> leal _48(,%eax,4), %eax
> things build again with the label being defined as
> .type $_48, @object
> .size $_48, 12
> $_48:
> and used like
> cmpl $$_48+12, %eax
> without problems.
>
> Do you believe this is a bug for leal in the older version of binutils
> (2.15) FreeBSD ships? I am surprised that it works when I remove the $.
It works only because "_48" will create a relocation to an external object. You
can see this by using 'objdump -dr init-list.o", where init-list.o is created
with "gcc -O2 -m32 -c -std=gnu++0x"
When this part is assembled (on linux!):
ja .L306
leal ._48(,%eax,4), %eax
movl %eax, 44(%esp)
subl $._48, %eax
sarl $2, %eax
An offset to an object in .data section is calculated at assembly time, so you
will get:
...
579: 0f 87 01 02 00 00 ja 780 <main+0x780>
57f: 8d 04 85 18 00 00 00 lea 0x18(,%eax,4),%eax
582: R_386_32 .data
586: 89 44 24 2c mov %eax,0x2c(%esp)
58a: 2d 18 00 00 00 sub $0x18,%eax
58b: R_386_32 .data
58f: c1 f8 02 sar $0x2,%eax
...
while removing "." (equivalent to removing "$" on BSD) from the lea operand
leaves an relocation to external symbol:
...
579: 0f 87 01 02 00 00 ja 780 <main+0x780>
57f: 8d 04 85 00 00 00 00 lea 0x0(,%eax,4),%eax
582: R_386_32 _48
586: 89 44 24 2c mov %eax,0x2c(%esp)
58a: 2d 18 00 00 00 sub $0x18,%eax
58b: R_386_32 .data
58f: c1 f8 02 sar $0x2,%eax
I found much more interesting the fact, that both:
subl ._48, %eax
and
subl $._48, %eax
produce the same result, while changing:
leal ._48(,%eax,4), %eax
to
leal $._48(,%eax,4), %eax
produces:
init-list.s: Assembler messages:
init-list.s:2664: Error: junk `(,%eax,4)' after expression
init-list.s:2664: Error: suffix or operands invalid for `lea'
I think that H.J. can explain the reason for this inconsistency in the
assembler.
--
ubizjak at gmail dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hjl dot tools at gmail dot
| |com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37520
