c - Platform-dependent behavior of fread with large nitems parameter -


i created test program below in attempt debug issue in larger system. program attempts fread large chunk of data small file, i've found behavior of program differs across platforms.

expected behavior

the behavior expect, , see on platforms (e.g., mac os x, centos 6.4), program read n bytes (the size of file) , terminate eof condition:

 read 2 bytes. ok. eof

anomalous behavior

on platforms (e.g., centos 6.6), program reports 0 bytes read , fails error:

 read 0 bytes. noooooooooooooo!!!! error: operation not permitted

on these platforms, can code work expected reducing chunk size "enough", i'm not sure how determine acceptable size programmatically...

questions

  • am using fread correctly?
  • is there more portable approach should using?
  • any suggested workarounds?

code

#include <stdlib.h> #include <stdio.h> #include <string.h>  int main(int argc, char* argv[]) {     file* file = fopen("test.txt", "rb");     size_t chunk = 0x7fffffff;     char* buf = malloc(chunk);     if (buf == null) {         printf("malloc failed\n");         return 1;     }     int count = fread(buf, 1, chunk, file);     printf("read %i bytes.\n", count);     int eof = feof(file);     if (eof) {         printf("ok. eof\n");     }     int err = ferror(file);     if (err) {         printf("noooooooooooooo!!!! error: %s\n", strerror(err));         return 1;     }     free(buf);     return 0; }

for test, created test.txt echo "a" >test.txt.


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