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[/] [or1k/] [trunk/] [gdb-5.0/] [mmalloc/] [sbrk-sup.c] - Rev 1770
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/* Support for sbrk() regions. Copyright 1992, 2000 Free Software Foundation, Inc. Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #ifdef HAVE_UNISTD_H #include <unistd.h> /* Prototypes for sbrk (maybe) */ #endif #include <string.h> /* Prototypes for memcpy, memmove, memset, etc */ #include "mmprivate.h" static PTR sbrk_morecore PARAMS ((struct mdesc *, int)); #if NEED_DECLARATION_SBRK extern PTR sbrk PARAMS ((int)); #endif /* The mmalloc() package can use a single implicit malloc descriptor for mmalloc/mrealloc/mfree operations which do not supply an explicit descriptor. For these operations, sbrk() is used to obtain more core from the system, or return core. This allows mmalloc() to provide backwards compatibility with the non-mmap'd version. */ struct mdesc *__mmalloc_default_mdp; /* Use sbrk() to get more core. */ static PTR sbrk_morecore (mdp, size) struct mdesc *mdp; int size; { PTR result; if ((result = sbrk (size)) == (PTR) -1) { result = NULL; } else { mdp -> breakval += size; mdp -> top += size; } return (result); } /* Initialize the default malloc descriptor if this is the first time a request has been made to use the default sbrk'd region. Since no alignment guarantees are made about the initial value returned by sbrk, test the initial value and (if necessary) sbrk enough additional memory to start off with alignment to BLOCKSIZE. We actually only need it aligned to an alignment suitable for any object, so this is overkill. But at most it wastes just part of one BLOCKSIZE chunk of memory and minimizes portability problems by avoiding us having to figure out what the actual minimal alignment is. The rest of the malloc code avoids this as well, by always aligning to the minimum of the requested size rounded up to a power of two, or to BLOCKSIZE. Note that we are going to use some memory starting at this initial sbrk address for the sbrk region malloc descriptor, which is a struct, so the base address must be suitably aligned. */ struct mdesc * __mmalloc_sbrk_init () { PTR base; unsigned int adj; base = sbrk (0); adj = RESIDUAL (base, BLOCKSIZE); if (adj != 0) { sbrk (BLOCKSIZE - adj); base = sbrk (0); } __mmalloc_default_mdp = (struct mdesc *) sbrk (sizeof (struct mdesc)); memset ((char *) __mmalloc_default_mdp, 0, sizeof (struct mdesc)); __mmalloc_default_mdp -> morecore = sbrk_morecore; __mmalloc_default_mdp -> base = base; __mmalloc_default_mdp -> breakval = __mmalloc_default_mdp -> top = sbrk (0); __mmalloc_default_mdp -> fd = -1; return (__mmalloc_default_mdp); }
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