[Pfspd-users@sf.net] Fw: [Pfspd-users@philips] pfspd file re-open

[Bram R. <bra...@nx...>]

Dear Jan, others,

Thanks for the excellent code exerpt that showed the problem.
Indeed, you isolated a bug that exists already for years.
It is now resolved in the code repository.

Here is the description from the Readme.txt.file:

- Application segmentation fault on Linux.
  Following calling sequence failed at the p_read_header() routine:
      p_create_header(&out_header, P_COLOR_444_PL, P_50HZ);
      p_write_header("test.yuv", &out_header);
      p_close_file("test.yuv");
      p_read_header("test.yuv", &out_header);
  More general: the program may crash when accessing a closed file
  in a different mode than it was previously used.
  Underlaying cause: when accessing a file in a different mode,
  it is first closed, then opened in the appropriate mode.
  This test was incomplete: erreonously, a closed file is closed
  again, effectively calling fclose(NULL). This is implementation
  specific; some platforms ignore fclose(NULL).


I guess this bug only surfaced now, because:
- use of p_open_file() and p_close_file() is rare
- use of these functions in different modes is even more rare
- the erronous behaviour is platform dependent
Anyhow, it is good that this is now resolved.


I could not find a workaround in the application.
Note that the problem is platform dependent, on HP, I know it will run ok.
I order to continue with your application, you can path a cpfspd release 
as follows.
The modification is in the first "if" statement.

File cpfspd_low.c
Routine p_get_file_pointer()

Old code:
        /* If open file found */
        if (idx != -1) {
            /* Opened as read, write access required? Close it */
            /* Opened as write, read access required? Close it */
            if ( ((mode != p_mode_read) && (p_files[idx].mode == 
p_mode_read)) ||
                 ((mode == p_mode_read) && (p_files[idx].mode == 
p_mode_write)) ) {
                p_close_idx(idx); /* Ignore status - we'll access the same 
file later */
            }
        }

New code:
        /* If open file found */
        if ((idx != -1) && (p_files[idx].fp != NULL)) {
            /* Opened as read, write access required? Close it */
            /* Opened as write, read access required? Close it */
            if ( ((mode != p_mode_read) && (p_files[idx].mode == 
p_mode_read)) ||
                 ((mode == p_mode_read) && (p_files[idx].mode == 
p_mode_write)) ) {
                p_close_idx(idx); /* Ignore status - we'll access the same 
file later */
            }
        }

Regards, Bram

--
Bram Riemens, Principal Scientist

Research, Systems and Algorithms
NXP Semiconductors
Office: WDC 3.41, Postbox WDC-03    <--- New address since Sept. 15, 2006
High Tech Campus 31, 5656 AE Eindhoven, The Netherlands
Tel: +31 40 27 43833, Fax: +31 40 27 44639
E-mail: bra...@nx...     www.nxp.com

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Jan Caussyn 
Sent by:
pfs...@gf...
27-10-2006 17:14

To
pfs...@gf...
cc

Subject
[Pfspd-users@philips] pfspd file re-open
Classification








Hi, 

Who has a solution to this one ?  In a certain case, I want to make a 
clean start with a certain file, so I close it using p_close_file. 
However, this causes an unhandled exception in a subsequent p_read_header. 

An example you find below : 

This crashes : 

#include "cpfspd.h" 
#include <stdlib.h> 

/* main declaration */ 
/************************************************************************/ 

int main(int argc,char *argv[]) 
{ 
        pT_header                out_header ; 
        pT_status                status ; 
 
 
          int                        xdim, ydim, nframes ; 
          int                        xcount, ycount, framecount ; 
 
    status = p_create_header (&out_header, P_COLOR_444_PL, P_50HZ) ; 
         status = p_write_header ("test.yuv", &out_header ); 

    p_close_file ("test.yuv") ; 

        status = p_read_header ("test.yuv", &out_header) ; 
        p_fatal_error_fileio (status, "test.yuv", stderr) ; 

        exit(0) ; 
}        

If you put the p_close_file line in comment, it works fine, but that is 
not what I am looking for. 
I tried 1.10.1, 1.9.2 and 1.8.2, it's all the same. 

Any comments appreciated, 
Regards, 
Jan 

__________________________________________________________

 Jan Caussyn                                             Philips 
Innovative Applications NV Brugge
 Phone : +32 (0)50 455 750                     Product Development 
 Fax      : +32 (0)50 455 722                     Entrance 2
 Pathoekeweg 11                                     B8000 Brugge, Belgium  
 
 mailto : jan...@ph...
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