Hi --
I don't think that a fix in GDB would be appropriate.
GDB is doing exactly what it should -- it places a breakpoint
at the first line in the function.
GCC should not output a line entry in the middle of the prologue.
Luis Machado wrote:
Hi,
Yes, this is exactly what i was chasing some time ago. The GCC fix i had
in mind (it just changes the ordering of statements) didn't get through
since it dealt with arch-independent code and there was fear that this
would break architectures other than PPC (or have the potential to do
so).
The breakpoint is placed at the wrong place due to the branch
instruction in the prologue. GDB just assumes that the second BB is real
code (not prologue anymore) since GCC never provided any useful
information on where exactly the prologue ends.
Original thread is here:
http://gcc.gnu.org/ml/gcc-patches/2009-02/msg01213.html
A fix on GDB's side proved to be harder than in GCC's side (since we're
already assuming things, it would just be another workaround).
Luis
On Tue, 2009-07-21 at 08:38 -0500, Peter Bergner wrote:
On Thu, 2009-07-16 at 13:55 -0700, Michael Eager wrote:
I've tracked down a failure in gdb to hit a breakpoint
set at printf to the the breakpoint being placed incorrectly.
Here is the code generated for printf with -mhard-float:
.loc 1 29 0
.cfi_startproc
.LVL0:
mflr 0
stwu 1,-112(1)
.LCFI0:
.cfi_def_cfa_offset 112
stw 5,24(1)
stw 0,116(1)
stw 6,28(1)
stw 7,32(1)
stw 8,36(1)
stw 9,40(1)
stw 10,44(1)
bne- 1,.L2 <<< - 1
.cfi_offset 65, 4
.loc 1 29 0 <<< - 2
stfd 1,48(1) <<< - 3
stfd 2,56(1)
stfd 3,64(1)
stfd 4,72(1)
stfd 5,80(1)
stfd 6,88(1)
stfd 7,96(1)
stfd 8,104(1)
.L2:
.loc 1 34 0
Gdb places a breakpoint at printf() at the stfd instruction (3).
This appears to be because of the .loc at (2). When the code is
executed, the branch (1) is taken, jumping over the the breakpoint.
I think that the .loc at (2) should not be generated, since it is
in the middle of the prologue code.
Luis, isn't there a bugzilla regarding this? This seems to me to
be similar to what you had been looking at.
Peter
--
Michael Eager ea...@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306 650-325-8077
