This is my function that seems to cause this more than anything else… it’s ridiculously simple…

Function ExtractFilePathAndNameWithoutExt(Filenametouse:String):String;
Begin
   ExtractFilePathAndNameWithoutExt := copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1);
End;

I stuck a bunch of Writeln’s in it to try to figure out what the heck is happening… my normal response when I need to track something down and the debug information is not clear.

Function ExtractFilePathAndNameWithoutExt(Filenametouse:String):String;
Begin
   Writeln('Filenametouse: ',Filenametouse);
   Writeln('ExtractFileExt(Filenametouse): ',ExtractFileExt(Filenametouse));
   Writeln('rpos(ExtractFileExt(Filenametouse),Filenametouse): ',rpos(ExtractFileExt(Filenametouse),Filenametouse));
   Writeln('Length(Filenametouse): ',Length(Filenametouse));
   Writeln('copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1): ',copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1));
   ExtractFilePathAndNameWithoutExt := copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1);
End;

The results I get when it fails are :

Writeln('Filenametouse: ',Filenametouse); This gives me what I expect: a valid filename with full path

Writeln('ExtractFileExt(Filenametouse): ',ExtractFileExt(Filenametouse)); This gives me what I expect: the extension only from the above file name

Writeln('rpos(ExtractFileExt(Filenametouse),Filenametouse): ',rpos(ExtractFileExt(Filenametouse),Filenametouse)); This is what’s causing the error… strangely it does the Writeln AFTER the error.. I don’t understand how that can even happen.

I tested this selecting the same 3 files over and over until it failed. Here is the Console output showing the last good set and the failre:

-------------------------------------- Console Output-----------------------------

M:\

elipse_1.dpax

elipse_2.dpax

elipse_3.dpax

4 Files Selected

Filenametouse: M:\elipse_1.dpax

ExtractFileExt(Filenametouse): .dpax

rpos(ExtractFileExt(Filenametouse),Filenametouse): 12

Length(Filenametouse): 16

copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1): M:\elipse_1

Drawing: M:\elipse_1

Filenametouse: M:\elipse_2.dpax

ExtractFileExt(Filenametouse): .dpax

rpos(ExtractFileExt(Filenametouse),Filenametouse): 12

Length(Filenametouse): 16

copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1): M:\elipse_2

Drawing: M:\elipse_2

Filenametouse: M:\elipse_3.dpax

ExtractFileExt(Filenametouse): .dpax

rpos(ExtractFileExt(Filenametouse),Filenametouse): 12

Length(Filenametouse): 16

copy(Filenametouse,1,rpos(ExtractFileExt(Filenametouse),Filenametouse)-1): M:\elipse_3

Drawing: M:\elipse_3

M:\

elipse_1.dpax

elipse_2.dpax

elipse_3

4 Files Selected

Filenametouse: M:\elipse_1.dpax

ExtractFileExt(Filenametouse): .dpax

An unhandled exception occurred at $0040ED1A:

EAccessViolation: Access violation

$0040ED1A

$004026DB main, line 119 of i:/programming/gcode/mill/plotdraw.pax.pas

rpos(ExtractFileExt(Filenametouse),Filenametouse):

--------------------------------------End Console Output-----------------------------

Does anyone have any idea at all why RPOS could not determine that the position of .dpax in M:\elipse_1.dpax was 12 like every other time I ran this????????????

I ran this while looking at task manager and it starts up with 9.2MB of memory and that stays consistent, so I don’t think I have a memory leak anywhere. Any ideas?? I’m running on Windows 10, compiling with FPC 3.0.4RC1 with the FPC text IDE.

James

Op 2019-05-21 om 14:18 schreef James Richters:

Start with assigning the result of the rpos to a variable and printing and reusing that.

To do anything we will need a compilable short fragment of code demonstrating the bug.

Sometimes this can be done by just taking the existing source and start removing code that doesn't seem to influence the code, and passing constants instead of whereever you get your filenames.

I'll try your ideas on how to track this down.

I wonder if I am really having some kind of other issue... maybe RPOS is using the stack and I'm running out of space or some other kind of memory issue. It seems odd that I can run this routine dozens of times successfully and then I get this access violation... with the exact same input it was fine with one loop earlier. I also have access violations in other procedures. I have a sequence that produces it here... but other sequences produce it in other places. Is there a way I can output various memory areas to see if it's really a memory related issue? Something like a writeln for stack space etc?

James

From LazFileUtils unit:

function ExtractFileNameWithoutExt(const AFilename: string): string;
var
  p: Integer;
begin
  Result:=AFilename;
  p:=length(Result);
  while (p>0) do begin
    case Result[p] of
      PathDelim: exit;
      {$ifdef windows}
      '/': if ('/' in AllowDirectorySeparators) then exit;
      {$endif}
      '.': exit(copy(Result,1, p-1));
    end;
    dec(p);
  end;
end;

writeln(ExtractFileNameWithoutExt('c:\foo\bar\foobar.ext')); gives:
c:\foo\bar\foobar

Thanks for the function. I don't think that my function is the problem at all.. I've just completed a test where I bypassed my file list and ran it several hundred times and my function never caused any problems.... I think I have a fundamental problem with the function I disabled to get it to work... maybe I am not cleaning up or resetting the way I should be. I'm going to post that function with a separate title to make it clear it's a new topic

James