minix/lib/libc/sys/brk.c

   1 #include <sys/cdefs.h>
   2 #include "namespace.h"
   3 #include <lib.h>
   4
   5 #include <string.h>
   6 #include <unistd.h>
   7
   8 #ifdef __weak_alias
   9 __weak_alias(brk, _brk)
  10 #endif
  11
  12 extern char *_brksize;
  13
  14 /* Both OSF/1 and SYSVR4 man pages specify that brk(2) returns int.
  15  * However, BSD4.3 specifies that brk() returns char*.  POSIX omits
  16  * brk() on the grounds that it imposes a memory model on an architecture.
  17  * On the other hand, they are so crucial to correct operation of so many
  18  * parts of the system, that we have chosen to hide the name brk using _brk,
  19  * as with system calls.  In this way, if a user inadvertently defines a
  20  * procedure brk, MINIX may continue to work because the true call is _brk.
  21  */
  22 int brk(addr)
  23 void *addr;
  24 {
  25   message m;
  26
  27   if (addr != _brksize) {
  28         memset(&m, 0, sizeof(m));
  29         m.m_lc_vm_brk.addr = addr;
  30         if (_syscall(VM_PROC_NR, VM_BRK, &m) < 0) return(-1);
  31         _brksize = addr;
  32   }
  33   return(0);
  34 }
  35