[SOLVED] TStringList.free does not really release memory?
lazarus / 34-Windows

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senglit · 2020-04-26 18:39

Hi all,

I have a procedure which is to find some files' location in a folder.
The structure of the folder is already known so that I used some
TStringList to store the result of each step. There are more than
20,000 subfolders in the sRootDir. And the number of subfolders will
grows up very quickly(aroud 500 more per day). So I checked carefull
if I use TStringList.Free procedure.

But still, every time when this procedure is called (around 1 time per
1 minute), I can see the used memory growing quickly (90MByte more
after each calling) in windows task manager.

Please help me to check if I made some stupid mistakes. Thanks

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 procedure
SearchFile(sRootDir: string);var  Found: integer;  SearchRec:
TSearchRec;  i,j:integer; 
SiteFolders,DayFolders,HourFolders,AudioFolders: TStringList;begin 
SiteFolders:=TStringList.Create;    DayFolders:=TStringList.Create; 
HourFolders:=TStringList.Create;  AudioFolders:=TStringList.Create; 
DoneFileList.Clear;  AudioFileList.Clear;  DataFileList.Clear;  Found
:= FindFirst(sRootDir + '\*', faDirectory, SearchRec);      while
Found = 0 do  begin    if  (SearchRec.Name <> '.') and
 (SearchRec.Name <> '..') then    begin      SiteFolders.Add(sRootDir
+ '\'+SearchRec.Name);    end;    Found := FindNext(SearchRec);  end; 
FindClose(SearchRec);   for i:=0 to SiteFolders.Count-1 do  begin   
Found := FindFirst(SiteFolders[i]+'\*', faDirectory, SearchRec);     
  while Found = 0 do    begin      if  (SearchRec.Name <> '.') and
 (SearchRec.Name <> '..') then      begin       
DayFolders.Add(SiteFolders[i]+'\'+SearchRec.Name);      end;     
Found := FindNext(SearchRec);    end;  end;  FindClose(SearchRec);  
for i:=0 to DayFolders.Count-1 do  begin    Found :=
FindFirst(DayFolders[i]+'\*', faDirectory, SearchRec);         while
Found = 0 do    begin      if  (SearchRec.Name <> '.') and
 (SearchRec.Name <> '..') then      begin       
HourFolders.Add(DayFolders[i]+'\'+SearchRec.Name);      end;     
Found := FindNext(SearchRec);    end;  end;  FindClose(SearchRec);  
for i:=0 to HourFolders.Count-1 do  begin    Found :=
FindFirst(HourFolders[i]+'\*', faAnyFile, SearchRec);    while Found =
0 do    begin      if (SearchRec.Attr = faDirectory) then      begin 
      if (SearchRec.Name = 'Audio') then                     begin   
      AudioFolders.Add(HourFolders[i]+'\'+SearchRec.Name);       
 end;      end      else begin                                       
    for j:=0 to DATA_TYPES.Count-1 do        begin          if
(DATA_TYPES[j]+'.bid' = SearchRec.Name) then                         
         if FileExists(HourFolders[i]+'\'+SearchRec.Name+'.done') then
                   begin             
DoneFileList.Add(HourFolders[i]+'\'+SearchRec.Name+'.done');         
 end            else begin             
DataFileList.Add(HourFolders[i] + '\' + SearchRec.Name);             
Inc(DataFileCount);            end;        end;      end;      Found
:= FindNext(SearchRec);    end;  end;  FindClose(SearchRec);   for
i:=0 to AudioFolders.Count-1 do  begin    Found :=
FindFirst(AudioFolders[i]+'\*', faAnyFile, SearchRec);    while Found
= 0 do    begin      if RightStr(SearchRec.Name,4)='.bid' then       
                             if
FileExists(AudioFolders[i]+'\'+SearchRec.Name+'.done') then          
  begin         
DoneFileList.Add(AudioFolders[i]+'\'+SearchRec.Name+'.done');       
end        else begin          AudioFileList.Add(AudioFolders[i] + '\'
+ SearchRec.Name);        end;      Found := FindNext(SearchRec);   
end;  end;  FindClose(SearchRec);   SiteFolders.Free; 
DayFolders.Free;  HourFolders.Free;  AudioFolders.Free;end;          
DoneFileList, DataFileList and AudioFolders are global vars.

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bytebites · 2020-04-26 18:48

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    for i:=0
to SiteFolders.Count-1 do  begin    Found :=
FindFirst(SiteFolders[i]+'\*', faDirectory, SearchRec);        while
Found = 0 do    begin      if  (SearchRec.Name <> '.') and
 (SearchRec.Name <> '..') then      begin       
DayFolders.Add(SiteFolders[i]+'\'+SearchRec.Name);      end;     
Found := FindNext(SearchRec);    end;    FindClose(SearchRec);<-- move
within for loop  end;

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flowCRANE · 2020-04-26 19:19

Shorter, safer and more readable usage of the FindFirst, FindNext and
FindClose looks like this:

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 if
FindFirst({parameters}) = 0 thentry  repeat    {usage of the found
item}  until FindNext({parameter}) <> 0;finally 
FindClose({parameter});end;
Follow this schema — you will avoid memory leaks.

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senglit · 2020-04-27 04:25

Quote from: bytebites on April 26, 2020, 08:48:49 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    for i:=0
to SiteFolders.Count-1 do  begin    Found :=
FindFirst(SiteFolders[i]+'\*', faDirectory, SearchRec);        while
Found = 0 do    begin      if  (SearchRec.Name <> '.') and
 (SearchRec.Name <> '..') then      begin       
DayFolders.Add(SiteFolders[i]+'\'+SearchRec.Name);      end;     
Found := FindNext(SearchRec);    end;    FindClose(SearchRec);<-- move
within for loop  end;  
It works perfectly! Thank you.

But I'm still confused that even I put this FindClose at wrong pace, I
still called it before the procedure is finished. So, the used memory
will growing when the procedure is called, but it should be released
before the 'end;'. Maybe there is something I don't know about
TSearchRec?

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senglit · 2020-04-27 04:26

Quote from: furious programming on April 26, 2020, 09:19:03 pmShorter,
safer and more readable usage of the FindFirst, FindNext and FindClose
looks like this:

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 if
FindFirst({parameters}) = 0 thentry  repeat    {usage of the found
item}  until FindNext({parameter}) <> 0;finally 
FindClose({parameter});end;
Follow this schema — you will avoid memory leaks.

Yes it looks more beautifull indeed. Thanks!

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PascalDragon · 2020-04-27 07:22

Quote from: senglit on April 27, 2020, 06:25:06 amBut I'm still
confused that even I put this FindClose at wrong pace, I still called
it before the procedure is finished. So, the used memory will growing
when the procedure is called, but it should be released before the
'end;'. Maybe there is something I don't know about TSearchRec?

Each call to FindFirst results in the creation of a new TSearchRec.
The function does not care about what you pass in, so a previously
initialized TSearchRec will leak. As you did so in your loop each loop
run except for the last you leaked a TSearchRec.

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flowCRANE · 2020-04-27 12:55

In addition, if you iterate over all the elements of a given
collection (e.g. list or array), you can use the for in loop — it will
be easier to use the iterator, and the code itself will be shorter.
So, in summary, you can do it in this way:

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 var 
Folder: String; {..} for Folder in SiteFolders do  if FindFirst(Folder
+ '\*', faDirectory, SearchRec) = 0 then  try    repeat      if
(SearchRec.Name <> '.') and (SearchRec.Name <> '..') then       
DayFolders.Add(Folder + '\' + SearchRec.Name);    until
FindNext(SearchRec) <> 0;  finally    FindClose(SearchRec);  end;

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senglit · 2020-04-28 06:21

Quote from: furious programming on April 27, 2020, 02:55:32 pmIn
addition, if you iterate over all the elements of a given collection
(e.g. list or array), you can use the for in loop — it will be easier
to use the iterator, and the code itself will be shorter. So, in
summary, you can do it in this way:

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 var 
Folder: String; {..} for Folder in SiteFolders do  if FindFirst(Folder
+ '\*', faDirectory, SearchRec) = 0 then  try    repeat      if
(SearchRec.Name <> '.') and (SearchRec.Name <> '..') then       
DayFolders.Add(Folder + '\' + SearchRec.Name);    until
FindNext(SearchRec) <> 0;  finally    FindClose(SearchRec);  end;
Rewrote the code following your instruction. It looks much beter now.
Thanks