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[RFC]: patch #2 for Sun C compiled target programs
- From: Michael Mueller <m dot mueller99 at kay-mueller dot de>
- To: gdb-patches at sources dot redhat dot com, binutils at sources dot redhat dot com
- Date: Fri, 18 Jun 2004 19:21:13 +0200
- Subject: [RFC]: patch #2 for Sun C compiled target programs
For Sun C compiled 64 bit target programs "print localvar" does not work
(PR gdb/1669).
I verified this against these compiler versions:
Sun C 5.5 2003/03/12
Forte Developer 7 C 5.4 2002/03/09
Sun WorkShop 6 update 2 C 5.3 2001/05/15
Sun WorkShop 6 2000/04/07 C 5.1
This is what happens:
GNU gdb 2004-06-17-cvs
Copyright 2004 Free Software Foundation, Inc.
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This GDB was configured as "sparc-sun-solaris2.8"...
(gdb) b main
Breakpoint 1 at 0x100000894: file p2.c, line 6.
(gdb) run
Starting program: /export/home/michaelm/gdb/gdb-6.1.patch/tst/p2
Breakpoint 1, main () at p2.c:6
6 int n = 7;
(gdb) p n
Cannot access memory at address 0x7ffff009
There are 2 different problems that need to be fixed. One might involve
binutils.
*** Problem 1 *************************************************
In dbxread.c function read_ofile_symtab macro INTERNALIZE_SYMBOL (nlist,
bufp, abfd) is called to set nlist.n_value (type bfd_vma = unsigned
long, size 64 bit) to the negative offset of a local variable inside the
stack frame. This offset is taken from bufp->e_value which is 4 bytes
(bfd_byte e_value[4]). This is the macro definition:
#define INTERNALIZE_SYMBOL(intern, extern, abfd) \
{ \
(intern).n_type = bfd_h_get_8 (abfd, (extern)->e_type); \
(intern).n_strx = bfd_h_get_32 (abfd, (extern)->e_strx); \
(intern).n_desc = bfd_h_get_16 (abfd, (extern)->e_desc); \
if (bfd_get_sign_extend_vma (abfd)) \
(intern).n_value = bfd_h_get_signed_32 (abfd, (extern)->e_value);\
else \
(intern).n_value = bfd_h_get_32 (abfd, (extern)->e_value); \
}
The problem is that bfd_get_sign_extend_vma returns 0 and the negative
value is not sign extended and turns into a large positive number.
There was a similar problem in the past for mips 64 bit:
The problem with stabs and sign extension
http://sources.redhat.com/ml/gdb/2001-08/msg00078.html
db/ChangeLog-2001:
2001-08-14 H.J. Lu (hjl@gnu.org)
It was fixed by introducing the call to bfd_get_sign_extend_vma into the
macro. Following this example one could fix this by changing binutils to
make bfd_get_sign_extend_vma return 1 for sparc solaris 64 bit.
Function bfd_get_sign_extend_vma is also called in dwarf2read.c and I
don't know what the effects of such a change would be there. I'm also
not sure if this it the intended use of bfd_get_sign_extend_vma.
As a temporary workaround I changed INTERNALIZE_SYMBOL to always call
bfd_h_get_signed_32 (see the appended dbxread.workaround).
*** Problem 2 *************************************************
Function sparc64_frame_base_address in sparc64-tdep.c needs to be fixed:
/* ??? Should we take BIAS into account here? */
return cache->base;
The answer to the question in comment is yes, see the appended patch.
2004-05-18 Michael Mueller <m.mueller99@kay-mueller.de>
* sparc64-tdep.c: fix PR gdb/1669, printing of 64 bit
local variables
Index: sparc64-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sparc64-tdep.c,v
retrieving revision 1.12
diff -c -p -r1.12 sparc64-tdep.c
*** sparc64-tdep.c 7 Jun 2004 02:02:55 -0000 1.12
--- sparc64-tdep.c 18 Jun 2004 12:41:26 -0000
*************** sparc64_frame_base_address (struct frame
*** 568,575 ****
struct sparc_frame_cache *cache =
sparc64_frame_cache (next_frame, this_cache);
! /* ??? Should we take BIAS into account here? */
! return cache->base;
}
static const struct frame_base sparc64_frame_base =
--- 568,574 ----
struct sparc_frame_cache *cache =
sparc64_frame_cache (next_frame, this_cache);
! return cache->base + BIAS;
}
static const struct frame_base sparc64_frame_base =
###### This is a WORKAROUND, not a proper patch: #######
*** dbxread.c.orig Fri Jun 18 14:56:56 2004
--- dbxread.c Fri Jun 18 14:56:55 2004
*************** stabs_seek (int sym_offset)
*** 852,861 ****
--- 852,865 ----
(intern).n_type = bfd_h_get_8 (abfd, (extern)->e_type); \
(intern).n_strx = bfd_h_get_32 (abfd, (extern)->e_strx); \
(intern).n_desc = bfd_h_get_16 (abfd, (extern)->e_desc); \
+ /*** workaround for Solaris sparc 64 \
if (bfd_get_sign_extend_vma (abfd)) \
+ ***/ \
(intern).n_value = bfd_h_get_signed_32 (abfd, (extern)->e_value); \
+ /*** workaround for Solaris sparc 64 \
else \
(intern).n_value = bfd_h_get_32 (abfd, (extern)->e_value); \
+ ***/ \
}
/* Invariant: The symbol pointed to by symbuf_idx is the first one