Hello, FPC developers' list

I made a simple gui lazarus application with a form and a button on it. I also wrote a function in the same unit:

function GetValue(c: Char): Integer;
begin
  Result := Ord(c);
end;

In the Button1 OnClick handler I have next code:

var
  I: integer;
begin
  I := Ord('a') + GetValue('a');
  ShowMessage(IntToStr(I));
end;

I wrote it to force compiler to generate code for GetValue and for Ord functions.

I break after that line (if I break before gdb will return 0) and now I want to evaluate GetValue('a'):

[gdb log]
<-data-evaluate-expression GetValue('a')>
^done,value="194"
(gdb)
<ptype GetValue('a')>
&"ptype GetValue('a')\n"
~"type = LONGINT\n"
^done
[/gdb log]

and evaluate Ord('a'):

[gdb log]
<-data-evaluate-expression Ord('a')>
&"No symbol \"Ord\" in current context.\n"
^error,msg="No symbol \"Ord\" in current context." [/gdb log]

and evaluate IntToStr(I):

[gdb log]
<-data-evaluate-expression IntToStr(I)>
&"too few arguments in function call\n"
^error,msg="too few arguments in function call"
[/gdb log]

Are that all gdb bugs or wrong debug info?

Best regards,
Paul Ishenin.

Ord() is not a regular function, it's implemented using compiler magic (just like chr(), write(), read(), val(), str(), ...). The debugger has no idea about what it is, or even that it exists. We might be able to fake it in the debug information by simply defining ord() as an alias for longint/int64 or so (although then it will of course also work in cases where the normal ord() expression would fail -- to solve that, you could of course also adapt gdb's Pascal parser).

a) even if gdb would not complain, you would probably get a crash because as mentioned before, on i386 FPC by default uses the completely non-standard "Borland fastcall" calling convention, for which gdb has no support (it would try to call it like a cdecl function; and we don't say in the DWARF info either that it uses an unsupported calling convention -- stabs has no way to say anything about used the calling convention)
b) at least I have never spent any time on trying to get gdb to recognize function call symbols (especially not in case of overloaded functions, like the above). So I can't say whether it's caused by errors in the debug info, missing support for overloaded functions in gdb's Pascal parser, something else, or all of those things.

In general, I would not count on being able to call FPC functions from inside a debugger any time soon (unless someone starts spending time on that; at least I am not interested in doing that right now).

Jonas