fwrite,fread - Is this a bug or a known feature

[Markus Bernhardt <Markus.Bernhardt@scmb.de>]

Hi,

once again I don't know whether this is the right list for this question.

We see a problem with the functions fwrite/fread from glibc under ia64.

Code:
f = fopen(key, "wb");
wrote_elements = fwrite((long*)(shm + table->ebene3Index), 
                        sizeof(char), 
                        table->ebene3Count, 
                        f);
fclose(f);

If we write anything below two giga elements (element size is one byte)
=> 2GB data everything works perfect.

Trace from gdb with table->ebene3Count = 2147483592 (Below 2GB)
1112      wrote_elements = fwrite((long*)(shm + table->ebene3Index), sizeof(char), table->ebene3Count, f);
(gdb) next
1113      fclose(f)
(gdb) print wrote_elements
$2 = 2147483592

OK !!

Trace from gdb with table->ebene3Count = 2147483656 (Over 2GB)
1112      wrote_elements = fwrite((long*)(shm + table->ebene3Index), sizeof(char), table->ebene3Count, f);
(gdb) next
1113      fclose(f)
(gdb) print wrote_elements
$1 = 0

Problems:
1. wrote_elements is 0
2. File on disk is only 2147483648 bytes big.
   It looks to me, that the file size is rounded down to a multiple of
   the pagesize (16KB).

The same happens, if you use fread to read the files in again.

Is this a known feature of fwrite/fread?

We compile using the falgs -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE.
Are they ok for ia-64?

Yours,
  markus