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gaddlord

Member

Registered: 2012-01-02

Posts: 8

Website

Any idea why memory leak is reported

I have the following code

var
  C: TSQLDatabase;

initialization

  sqlite3_initialize; // so sqlite3.c is compiled with SQLITE_OMIT_AUTOINIT defined

  C := TSQLDatabase.Create('C:\database.db3');
  C.DBOpen;

finalization

  C.DBClose;
  FreeAndNil(C);

  sqlite3_shutdown;

at the end of SynSQLite3.pas

It generates:

--------------------------------2012/1/8 18:17:15--------------------------------
This application has leaked memory. The small block leaks are (excluding expected leaks registered by pointer):

21 - 36 bytes: Unknown x 6
37 - 52 bytes: Unknown x 4
53 - 68 bytes: Unknown x 3
69 - 84 bytes: Unknown x 3
85 - 100 bytes: Unknown x 3
485 - 532 bytes: Unknown x 2
1013 - 1124 bytes: Unknown x 1

for

This block was allocated by thread 0xE90, and the stack trace (return addresses) at the time was:
804AEA [System][@GetMem][34]
D0D61C [SynSQLite3.pas][SynSQLite3][@Synsqlite3_malloc][1934]
D108FF [SynSQLite3]
D11013 [SynSQLite3][@Synsqlite3_sqlite3_memory_highwater]
D1147B [SynSQLite3][@Synsqlite3_sqlite3_realloc]
D1143E [SynSQLite3][@Synsqlite3_sqlite3_realloc]
D3BB54 [SynSQLite3][@Synsqlite3_sqlite3_set_authorizer]
D55FC4 [SynSQLite3][@Synsqlite3_sqlite3_errmsg]
D560B8 [SynSQLite3][@Synsqlite3_sqlite3_open]
D0E17E [SynSQLite3.pas][SynSQLite3][TSQLDatabase.DBOpen][2677]
D0DC47 [SynSQLite3.pas][SynSQLite3][TSQLDatabase.$bctr][2394]

Any idea why this happens?

Last edited by gaddlord (2012-01-08 16:15:01)

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,660

Website

Re: Any idea why memory leak is reported

No need to call sqlite3_initialize.

It is already done in the initialization section of the SynSQLite3 unit.

gaddlord

Member

Registered: 2012-01-02

Posts: 8

Website

Re: Any idea why memory leak is reported

The code snippet was added exactly in the SynSQLite3.pas unit.

I added this there to show case how to achieve this.

A chopped down to the bare minimum version which demostrates the issue is available at http://dl.dropbox.com/u/3607590/TestSynSQLiteLeak.zip

Seems that 23 malloc Pointers are not having their Free functions called.

Can this be related to a known "pseudo leak" from the past as described here http://old.nabble.com/memory-leak-on-sq … 29415.html?

Last edited by gaddlord (2012-01-08 18:34:12)

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,660

Website

Re: Any idea why memory leak is reported

You initialize sqlite3_initialize twice!
The one present in SynSQLite3 is enough.

You download link just does not work.
I compiled the following program:

procedure Test;
var
  C: TSQLDatabase;
begin
  C := TSQLDatabase.Create('D:\Dev\lib\SQLite3\exe\test.db3');
  C.Free;
end;

And it works OK.

Issue in your code is that TSQLDatabase.Create already makes a C.DBOpen.
It is clearly stated by its documentation: "open an existing database file or create a new one if no file exists".

The DBOpen/DBClose functions are to be used only if you want to close then reopen the DB (for backup purposes, e.g.).
A possible working scheme could be:

procedure Test;
var
  C: TSQLDatabase;
begin
  C := TSQLDatabase.Create('D:\Dev\lib\SQLite3\exe\test.db3'); // open the DB
  C.DBClose; // close it
  C.DBOpen; // re-open DB
  C.DBClose; // close it (not necessary: C.Destroy calls DBClose)
  C.Free;
end;

I've added some description to DBOpen/DBClose to make it clear.

gaddlord

Member

Registered: 2012-01-02

Posts: 8

Website

Re: Any idea why memory leak is reported

Please disregard. It turned out to be a dummy error in my code which had oveload instead of override in my custom Reader destructor which never got called and finalization of statements never executed.

My bad.