memory.c   [plain text]

/* Memory mamagement routines.
   Copyright 2002 Free Software Foundation, Inc.
   Contributed by Paul Brook <paul@nowt.org>

This file is part of the GNU Fortran 95 runtime library (libgfor).

Libgfor is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

Libgfor 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with libgfor; see the file COPYING.LIB.  If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "config.h"
#include <stdlib.h>
#include "libgfortran.h"

/* If GFC_CLEAR_MEMORY is defined, the memory allocation routines will
   return memory that is guaranteed to be set to zero.  This can have
   a severe efficiency penalty, so it should never be set if good
   performance is desired, but it can help when you're debugging code.  */
#define GFC_CLEAR_MEMORY

/* If GFC_CHECK_MEMORY is defined, we do some sanity checks at runtime.
   This causes small overhead, but again, it also helps debugging.  */
#define GFC_CHECK_MEMORY

/* We use a double linked list of these structures to keep track of
   the memory we allocate internally.  We could also use this for user
   allocated memory (ALLOCATE/DEALLOCATE).  This should be stored in a
   seperate list.  */
#define malloc_t	prefix(malloc_t)
typedef struct malloc_t
{
  int magic;
  int marker;
  struct malloc_t *prev, *next;

  /* The start of the block.  */
  void *data;
}
malloc_t;

/* We try to make sure we don't get memory corruption by checking for
   a magic number.  */
#define GFC_MALLOC_MAGIC 0x4d353941	/* "G95M" */

#define HEADER_SIZE offsetof (malloc_t, data)
#define DATA_POINTER(pheader) (&((pheader)->data))
#define DATA_HEADER(pdata) ((malloc_t *)((char *) (pdata) - HEADER_SIZE))

/* The root of the circular double linked list for compiler generated
   malloc calls.  */
static malloc_t mem_root;


void
memory_init (void)
{

  /* The root should never be used directly, so don't set the magic.  */
  mem_root.magic = 0;
  mem_root.next = &mem_root;
  mem_root.prev = &mem_root;
  mem_root.marker = 0;
}


/* Doesn't actually do any cleaning up, just throws an error if something
   has got out of sync somewhere.  */

void
runtime_cleanup (void)
{
  /* Make sure all memory we've allocated is freed on exit.  */
  if (mem_root.next != &mem_root)
    runtime_error ("Unfreed memory on program termination");
}



void *
get_mem (size_t n)
{
  void *p;

#ifdef GFC_CLEAR_MEMORY
  p = (void *) calloc (n, 1);
#else
#define temp malloc
#undef malloc
  p = (void *) malloc (n);
#define malloc temp
#undef temp
#endif
  if (p == NULL)
    os_error ("Memory allocation failed");

  return p;
}


void
free_mem (void *p)
{

  free (p);
}


/* Allocates a block of memory with a size of N bytes.  N does not
   include the size of the header.  */

static malloc_t *
malloc_with_header (size_t n)
{
  malloc_t *newmem;

  n = n + HEADER_SIZE;

  newmem = (malloc_t *) get_mem (n);

  if (newmem)
    {
      newmem->magic = GFC_MALLOC_MAGIC;
      newmem->marker = 0;
    }

  return newmem;
}


/* Allocate memory for internal (compiler generated) use.  */

void *
internal_malloc_size (size_t size)
{
  malloc_t *newmem;

  newmem = malloc_with_header (size);

  if (!newmem)
    os_error ("Out of memory.");

  /* Add to end of list.  */
  newmem->next = &mem_root;
  newmem->prev = mem_root.prev;
  mem_root.prev->next = newmem;
  mem_root.prev = newmem;

  return DATA_POINTER (newmem);
}


void *
internal_malloc (GFC_INTEGER_4 size)
{
#ifdef GFC_CHECK_MEMORY
  /* Under normal circumstances, this is _never_ going to happen!  */
  if (size < 0)
    runtime_error ("Attempt to allocate a negative amount of memory.");

#endif
  return internal_malloc_size ((size_t) size);
}


void *
internal_malloc64 (GFC_INTEGER_8 size)
{
#ifdef GFC_CHECK_MEMORY
  /* Under normal circumstances, this is _never_ going to happen!  */
  if (size < 0)
    runtime_error ("Attempt to allocate a negative amount of memory.");
#endif
  return internal_malloc_size ((size_t) size);
}


/* Free internally allocated memory.  Pointer is NULLified.  Also used to
   free user allocated memory.  */
/* TODO: keep a list of previously allocated blocks and reuse them.  */

void
internal_free (void *mem)
{
  malloc_t *m;

  if (!mem)
    runtime_error ("Internal: Possible double free of temporary.");

  m = DATA_HEADER (mem);

  if (m->magic != GFC_MALLOC_MAGIC)
    runtime_error ("Internal: No magic memblock marker.  "
		   "Possible memory corruption");

  /* Move markers up the chain, so they don't get lost.  */
  m->prev->marker += m->marker;
  /* Remove from list.  */
  m->prev->next = m->next;
  m->next->prev = m->prev;

  free (m);
}


/* User-allocate, one call for each member of the alloc-list of an
   ALLOCATE statement. */

static void
allocate_size (void **mem, size_t size, GFC_INTEGER_4 * stat)
{
  malloc_t *newmem;

  if (!mem)
    runtime_error ("Internal: NULL mem pointer in ALLOCATE.");

  newmem = malloc_with_header (size);
  if (!newmem)
    {
      if (stat)
	{
	  *stat = 1;
	  return;
	}
      else
	runtime_error ("ALLOCATE: Out of memory.");
    }

  /* We don't keep a list of these at the moment, so just link to itself. */
  newmem->next = newmem;
  newmem->prev = newmem;

  (*mem) = DATA_POINTER (newmem);

  if (stat)
    *stat = 0;
}


void
allocate (void **mem, GFC_INTEGER_4 size, GFC_INTEGER_4 * stat)
{

  if (size < 0)
    {
      runtime_error ("Attempt to allocate negative amount of memory.  "
		     "Possible integer overflow");
      abort ();
    }

  allocate_size (mem, (size_t) size, stat);
}


void
allocate64 (void **mem, GFC_INTEGER_8 size, GFC_INTEGER_4 * stat)
{

  if (size < 0)
    {
      runtime_error
	("ALLOCATE64: Attempt to allocate negative amount of memory. "
	 "Possible integer overflow");
      abort ();
    }

  allocate_size (mem, (size_t) size, stat);
}


/* User-deallocate; pointer is NULLified. */

void
deallocate (void **mem, GFC_INTEGER_4 * stat)
{

  if (!mem)
    runtime_error ("Internal: NULL mem pointer in ALLOCATE.");

  if (!*mem)
    {
      if (stat)
	{
	  *stat = 1;
	  return;
	}
      else
	{
	  runtime_error
	    ("Internal: Attempt to DEALLOCATE unallocated memory.");
	  abort ();
	}
    }

  /* Just use the internal routine.  */
  internal_free (*mem);
  *mem = NULL;

  if (stat)
    *stat = 0;
}