minix/lib/other/_brk.c

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2005-04-21 16:53:53 +02:00
#include <lib.h>
#define brk _brk
#define sbrk _sbrk
#include <unistd.h>
extern char *_brksize;
/* Both OSF/1 and SYSVR4 man pages specify that brk(2) returns int.
* However, BSD4.3 specifies that brk() returns char*. POSIX omits
* brk() on the grounds that it imposes a memory model on an architecture.
* For this reason, brk() and sbrk() are not in the lib/posix directory.
* On the other hand, they are so crucial to correct operation of so many
* parts of the system, that we have chosen to hide the name brk using _brk,
* as with system calls. In this way, if a user inadvertently defines a
* procedure brk, MINIX may continue to work because the true call is _brk.
*/
PUBLIC int brk(addr)
char *addr;
{
message m;
if (addr != _brksize) {
m.m1_p1 = addr;
if (_syscall(MM, BRK, &m) < 0) return(-1);
_brksize = m.m2_p1;
}
return(0);
}
PUBLIC char *sbrk(incr)
int incr;
{
char *newsize, *oldsize;
oldsize = _brksize;
newsize = _brksize + incr;
if ((incr > 0 && newsize < oldsize) || (incr < 0 && newsize > oldsize))
return( (char *) -1);
if (brk(newsize) == 0)
return(oldsize);
else
return( (char *) -1);
}