gif Problem (used version is giflib 4.1.6). about leptonica HOT 18 CLOSED

Upon investigation, there is a memory leak in 1.65 of the fp struct (568 bytes 
in
linux) for each read and write.

This is due to not calling fclose(fp) for GIF reading and writing.
And that was put in a couple of years ago when we first started supporting GIF,
and were using an older, buggy version of giflib that called fclose(fp)
when the gif struct was destroyed.  Yes, hard to believe.

Anyway, this leak goes away when the streams are closed.
To patch:
  remove l. 164 in readfile.c
  remove l. 243 in writefile.c

Let me know if that solves the halting problem on windows.

This will be fixed in 1.66.

Hi,
As i understand, i've removed the lines  "164 in readfile.c" and "243 in 
writefile.c
" respectively:

removed the line 164 in readfile.c which is like below by commenting the line: 
if (pixGetInputFormat(pix) != IFF_GIF)  /* DGifCloseFile() closes stream! */

removed the line 243 in writefile.c which is like below by commenting the line:
if (format != IFF_GIF)  /* EGifCloseFile() closes file stream! */

Result is again a halting prpblem when i try to read gif files (writing is not
tested). Before, i could read and display the gif files, but problem occurs 
when the
program is closed, and now, when i try to read the gif file, the halting problem
occurs immediately. 

If i remove the correct lines from readfile.c and writefile.c, so what can be 
done
more to solve the fault?

Thanks for your considerations.

OK, you've removed the conditional lines, so that the stream is explicitly 
closed
with fclose() for both reading and writing GIF files.

When you say "halting problem", do you mean that the program hangs (as if it 
went
into an infinite loop), or that it crashes, or what?

What compiler are you using on windows?

Hi,

I've compiled Leptonica_v1-65 using VS2008 as a DLL file. If i use the modified
readfile.c/writefile.c then test program crashes when i try to read a gif file
immediately, so the program halts.

Before, without modifying two of these files, i could read and display, but the
program crashes when closing the program.

I think there is a problem with pixReadStream(). In the readfile.c:

...
    case IFF_GIF:
        if ((pix = pixReadStreamGif(fp)) == NULL)
...

there can be a problem in pixReadStreamGif(fp).


Thanks.

There is a specific section in the VS2008 Notes on adding giflib 4.1.6 support 
to
Leptonica at http://www.leptonica.org/vs2008doc/building-giflib.html. I've only
tested it on Windows XP Pro, however, I did verify that the gifio_reg program 
runs
correctly (that's how I got the screenshot at the bottom of the page).

Can you build & run gifio_reg without errors?

Hi,

I guess that the gif file (GifFileType * GifFile struct) must be closed when 
reading
using DGifCloseFile( GifFileType * GifFile ) and using EGifCloseFile( 
GifFileType *
GifFile ) if writing.

Looks to me like DGifCloseFile() in dgif_lib.c at line 610 still does:

    if (File && (fclose(File) != 0)) {
        _GifError = D_GIF_ERR_CLOSE_FAILED;
        return GIF_ERROR;
    }

And EGifCloseFile() in egif_lib.c at line 760 also does:

    if (File && fclose(File) != 0) {
        _GifError = E_GIF_ERR_CLOSE_FAILED;
        return GIF_ERROR;
    }

So readfile.c & writefile.c were correct in 1.65. Changing them as suggested in
Comment 1 would result in the same errors resolved in Issue 28
(http://code.google.com/p/leptonica/issues/detail?id=28&can=1)

Maybe this is some difference between giflib 4.1.6 and libungif 4.1.4 (which 
are NOT
the same thing). giflib 4.1.6 is newer so that's what I used.

Yes, it could be a 4.1.6 vs ungiflib 4.1.4 issue.

But we have this situation on 4.1.6:

(a) with the patch of 28:

  linux: memory leak of about 600 bytes (the stream) on each read and write.
  windows: perhaps it leaks here as well?

(b) without the patch of 28:

  linux: no memory leak and no memory corruption (e.g., there is no double-free
      of the stream!)
  windows: crashes

giflib seems to be stashing a "private" version of the ptr to fp, and using
it to close the stream, as you pointed out in dgif_lib.c.

This is baffling.  Should we close the stream in linux but not in windows?

I wrote a little testing program:

    FILE *fp = fopen("marge.gif", "rb");
    l_int32 fd = fileno(fp);
    fprintf(stderr, "fd = %d\n", fd);
    FILE *fp2 = fdopen(fd, "rb");
    fprintf(stderr, "fp = %x, fp2 = %x\n", fp, fp2);
    fclose(fp2);
    fclose(fp);

As expected, fdopen makes a new stream object.  That's why it
is necessary in linux to fclose(fp) -- because the stream that
is closed by DGifCloseFile() is a different stream, private to the 'GifFile'.
Each stream that is not closed causes a memory leak of 568 bytes.

The only difference in windows is line 120 in dgif_lib.c, where
setvbuf is called to associate a new buffer with the stream.
But I don't understand what's really happening there.

The VS2008 documentation on setvbuf() is at
http://msdn.microsoft.com/en-us/library/86cebhfs%28VS.90%29.aspx.

Seems harmless enough with the only question being what happens to the 
"automatically
allocated" buffer. Presumably it is "automatically" freed when the stream is 
closed.

I would still like to hear if the OP built and ran gifio_reg without errors. 
Like I
said, it works fine for me.

To remove the linux error leak, we can put this code in readfile.c (and similar
in writefile.c):

        /* Close the stream except if GIF under windows, because
         * DGifCloseFile() closes the windows file stream! */
    if (pixGetInputFormat(pix) != IFF_GIF)
        fclose(fp);
#ifndef COMPILER_MSVC
    else  /* gif file */
        fclose(fp);
#endif  /* !COMPILER_MSVC */

w/ issue 36: yes, it would be very useful to be able to find
memory leaks in windows, esp. in cases such as this where the
low-level calls differ from linux.

the changes described above were just released with 1.66.

Does this solve all the crash problems in windows, so we can close this?

I was able to run gifio_reg without any problems so I would say yes. If the 
original poster still finds a problem he'll need to re-open the issue.

Hi,
Leptonlib v1.66 is very good and gif problem is fixed, i've tested (OS: Vista 
Home Premium, the library is compiled in VStudio2008 IDE, tested in a simple 
VC++ program and second test done using a delphi executable).

Good and fast.
Thanks for All.
Fatih.

Hi, I need delphi wrapper for Leptonica!  Can You send me please this wrapper? 
And you'r vs2008 project for leptonica?
Mail to: [email protected]
Best regards, Andrew Smirnov

I don't use Delphi myself but I believe the best approach would be to download 
the Leptonica pre-built binaries for Windows (32-bit) from 
http://www.leptonica.org/source/leptonica-1.66-win32-lib-include-dirs.zip and 
use leptonlib.dll from Delphi.

See "Using C DLLs with Delphi" (http://www.drbob42.com/delphi/headconv.htm) for 
details on how you do this. There is also a tool called HeadConv aka "Project 
JEDI Header Converter utility" that you can get from 
http://www.delphi-jedi.org/api-howto.html that will apparently automatically 
create the Delphi wrapper stuff you need.

Download the vs2008 project from 
http://www.leptonica.org/source/vs2008-1.66.zip (although that's mainly if you 
need to rebuild the leptonica.dll for some reason).