[fpc-devel] Invalid line-info on array of const

[Joost van der Sluis]

Hi all,

I think I've found a bug while testing the fpdebug-debugger. The 
line-info for the attached program is not entirely correct, I think.

Here's the generated assembly:

# [12] case i of
         movl    -12(%rbp),%eax
         testl   %eax,%eax
         jl      .Lj10
         testl   %eax,%eax
         jne     .Lj10
         jmp     .Lj9
.Lj10:
.Ll5:
# [18] writeln('hallo');
         call    fpc_get_output
         movq    %rax,%rbx
         movq    $_$PROJECT4$_Ld1,%rdx
         movq    %rbx,%rsi
         movl    $0,%edi
         call    fpc_write_text_shortstr
         call    FPC_IOCHECK
         movq    %rbx,%rdi
         call    fpc_writeln_end
         call    FPC_IOCHECK
.Lj9:
.Lj5:
         call    FPC_POPADDRSTACK
.Ll6:
# [20] end;
         leaq    -24(%rbp),%rdi
         call    fpc_ansistr_decr_ref
         movq    -120(%rbp),%rax
         testq   %rax,%rax
         je      .Lj6
         call    FPC_RERAISE
.Lj6:
         movq    -128(%rbp),%rbx
         leave
         ret

As you can see, according to the line-info the call to FPC_POPADDRSTACK 
belongs to the writeln. But the jump in the case goes to label Lj9.

Imaging stepping through this procedure. When the writeln is skipped, 
the 'call fpc_popaddrstack' is the next command. And the debugger will 
think that the 'writeln' is the current command. (ie: the debugger jumps 
from line 12 to 18. Even if line 18 is never executed)

Gdb does not show this. I think because it also checks if the current 
instruction pointer is at the start of the line as given in the debug 
info. FpDebug also does that check in some cases, but not in this case 
since it should not be necessary. At least so I thought.

I can add this check to the debugger anyway, but am I right that the 
line info in the example is wrong? Then I can try to fix it.

Joost.
-------------- next part --------------
program project4;

uses
  sysutils;

function Test: string;
var
  i: Integer;
  AValue: string;
begin
  i := 0;
  case i of
    0: begin
         if false then
           raise exception.CreateFmt('Test',[AValue]);
       end
  else
    writeln('hallo');
  end;
end;

begin
  test;
end.