Incorrect result of function FileAge, when date 12-30-1899
lazarus / 66-Unix

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7bit · 2025-02-23 08:14

I found that if the file modification date in the system is 12/30/1899
(TDateTime value = 0), the FileAge returns an incorrect result. Here
is the code that demonstrates the problem:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
Unit1; {$mode objfpc}{$H+} interface uses  Classes, SysUtils,
LResources, Forms, Controls, Graphics, Dialogs, StdCtrls,  BaseUnix,
DateUtils; type   { TForm1 }   TForm1 = class(TForm)    Button1:
TButton;    procedure Button1Click(Sender: TObject);  private  
public   end; var  Form1: TForm1; implementation { TForm1 } procedure
TForm1.Button1Click(Sender: TObject);var  FlNm: String;  Utime:
UtimBuf;  St: stat;begin  FlNm := GetTempDir + 'temp.tmp';  with
TFileStream.Create(FlNm, fmCreate) do  begin    Free;  end;  
//UTime.modtime := DateTimeToUnix(StrToDateTime('30-12-1901')); 
UTime.modtime := DateTimeToUnix(0);  UTime.actime := UTime.modtime; 
FpUtime(FlNm, @Utime);   // invalid time 
ShowMessage(FormatDateTime('dd-mm-yyyy',
UnixToDateTime(FileAge(FlNm))));   // valid time  FpStat(FlNm, St); 
ShowMessage(FormatDateTime('dd-mm-yyyy',
UnixToDateTime(St.st_mtime)));end; initialization  {$I
unit1.lrs} end.                                              
Lazarus/FPC version: Lazarus 4.0RC2 (rev
lazarus_4_0RC2-104-gb0513d9031) FPC 3.2.2 x86_64-linux-gtk2

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MarkMLl · 2025-02-23 09:01

What happens if that's a simple non-GUI program? What date does the OS
show for the file? Is it different depending on what utility you use?
What filesystem are you using? Does the date survive an fsck?

I'm troubled by the fact that unix- in general- has no support for
files older than its own epoch, so trying to force things might lead
to inconsistent results.

MarkMLl

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7bit · 2025-02-23 11:13

Here is a simple program:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
project1; uses  SysUtils, Classes, BaseUnix, DateUtils; var  FlNm:
String;  Utime: UtimBuf;  St: stat;begin  FlNm := GetTempDir +
'temp.tmp';  with TFileStream.Create(FlNm, fmCreate) do  begin   
Free;  end;   UTime.modtime := DateTimeToUnix(0);  UTime.actime :=
UTime.modtime;  FpUtime(FlNm, @Utime);   // invalid time 
WriteLn(FormatDateTime('dd-mm-yyyy',
UnixToDateTime(FileAge(FlNm))));   // valid time  FpStat(FlNm, St); 
WriteLn(FormatDateTime('dd-mm-yyyy',
UnixToDateTime(St.st_mtime)));end.    The result is the same.

File system is Ext4.

Ouput of command ls -l:

Code: Bash  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i #ls -l-rw-r
--r-- 1 user user  0 дек 30  1899 temp.tmp 
Result fsck i not check.

Incorrect result of function FileAge, because it does not fit into the
LongInt type. The Int64 type is required for the result.

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MarkMLl · 2025-02-23 11:44

Quote from: 7bit on February 23, 2025, 12:13:38 pmIncorrect result of
function FileAge, because it does not fit into the LongInt type. The
Int64 type is required for the result.

Well deduced, in that case raise a bug report.

MarkMLl

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Remy Lebeau · 2025-02-23 19:10

What about using the FileAge() overload that outputs a TDateTime 
instead of an integer?