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* i386-tdep.c: Add FIXME regarding STABS vs. Dwarf 2 register

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numbering.
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Jim Blandy 2004-04-01 18:14:03 +00:00
parent f86ef5a3a2
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@ -1,3 +1,8 @@
2004-04-01 Jim Blandy <jimb@redhat.com>
* i386-tdep.c: Add FIXME regarding STABS vs. Dwarf 2 register
numbering.
2004-04-01 Paul N. Hilfinger <Hilfinger@gnat.com>
* valarith.c: Update copyright notice.

36
gdb/i386-tdep.c
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@ -166,6 +166,42 @@ i386_register_name (int reg)
return NULL;
}
/* FIXME: jimb/2004-04-01: I don't think these functions are right.
For a given platform, GCC always uses the same register numbering
in both STABS and Dwarf2: gcc/dbxout.c and gcc/dwarf2out.c both use
the DBX_REGISTER_NUMBER macro, as defined by the config headers.
If you compile a program so that its variables are allocated to
floating-point registers, first with STABS and again with Dwarf 2,
you'll see that the variable's register numbers are the same in
each case.
GCC does use (at least) two different register numberings on the
i386; they differ in how they number %ebp, %esp, %eflags, and the
floating-point registers. And it has a third numbering for "64bit
mode", which I assume is x86_64. But it always uses a given
numbering in both STABS and Dwarf.
This does not match the arrangement we have below, which presumes
that STABS and Dwarf numberings are different, and does some
strange mixing and matching (e.g., registering the Dwarf 2 function
as the STABS function for "Generic i386 ELF") to get close enough
to the right effect on the platforms we care about.
If we wanted to match GCC, we should have two separate register
number translation functions (we handle x86_64 in a separate tdep
file altogether), one corresponding to each of GCC's i386 register
maps. And for a given platform, we would register one of them as
both the STABS and Dwarf 2 functions.
However, we don't aspire to match GCC; we aspire to match the
native system's tools. I don't have access to lots of different
native compilers and debuggers to verify that GCC is matching their
behavior in this regard. Is it sufficient to argue that we at
least want to match GNU's compiler, and say we'll fix bugs relative
to native tools as they're reported? */
/* Convert stabs register number REG to the appropriate register
number used by GDB. */