lib/other/_brk.c

   1 #include <lib.h>
   2 #define brk     _brk
   3 #define sbrk    _sbrk
   4 #include <unistd.h>
   5
   6 extern char *_brksize;
   7
   8 /* Both OSF/1 and SYSVR4 man pages specify that brk(2) returns int.
   9  * However, BSD4.3 specifies that brk() returns char*.  POSIX omits
  10  * brk() on the grounds that it imposes a memory model on an architecture.
  11  * For this reason, brk() and sbrk() are not in the lib/posix directory.
  12  * On the other hand, they are so crucial to correct operation of so many
  13  * parts of the system, that we have chosen to hide the name brk using _brk,
  14  * as with system calls.  In this way, if a user inadvertently defines a
  15  * procedure brk, MINIX may continue to work because the true call is _brk.
  16  */
  17 PUBLIC int brk(addr)
  18 char *addr;
  19 {
  20   message m;
  21
  22   if (addr != _brksize) {
  23         m.m1_p1 = addr;
  24         if (_syscall(MM, BRK, &m) < 0) return(-1);
  25         _brksize = m.m2_p1;
  26   }
  27   return(0);
  28 }
  29