malloc.c

对内存的分配、释放和使用进行检查

/*
 * (c) Copyright 1990 Conor P. Cahill (uunet!virtech!cpcahil).  
 * You may copy, distribute, and use this software as long as this
 * copyright statement is not removed.
 */
#include <stdio.h>
#include <fcntl.h>
#include "malloc.h"
#include "tostring.h"

/*
 * Function:	malloc()
 *
 * Purpose:	memory allocator
 *
 * Arguments:	size	- size of data area needed
 *
 * Returns:	pointer to allocated area, or NULL if unable
 *		to allocate addtional data.
 *
 * Narrative:
 *
 */
#ifndef lint
static
char rcs_hdr[] = "$Id: malloc.c,v 1.6 90/05/11 00:13:09 cpcahil Exp $";
#endif

int		  malloc_checking;
char		* malloc_data_start;
char		* malloc_data_end;
struct mlist 	* malloc_end;
int		  malloc_errfd = 2;
int		  malloc_errno;
int		  malloc_fatal_level = M_HANDLE_CORE;
struct mlist	  malloc_start;
int		  malloc_warn_level;

char *
malloc(size)
	unsigned int	  size;
{
	char		* func = "malloc";
	char		* getenv();
	void		  malloc_fatal();
	void		  malloc_init();
	void		  malloc_memset();
	void		  malloc_split();
	void		  malloc_warning();
	unsigned int	  need;
	struct mlist	* oldptr;
	struct mlist	* ptr;
	char		* sbrk();

	/*
	 * If this is the first call to malloc...
	 */
	if( malloc_data_start == (char *) 0 )
	{
		malloc_init();
	}

	/*
	 * If malloc chain checking is on, go do it.
	 */
	if( malloc_checking )
	{
		(void) malloc_chain_check(1);
	}

	/*
	 * always make sure there is at least on extra byte in the malloc
	 * area so that we can verify that the user does not overrun the
	 * data area.
	 */
	size++;

	/*
	 * Now look for a free area of memory of size bytes...
	 */
	oldptr = NULL;
	for(ptr = &malloc_start; ; ptr = ptr->next)
	{
		/*
		 * Since the malloc chain is a forward only chain, any
		 * pointer that we get should always be positioned in 
		 * memory following the previous pointer.  If this is not
		 * so, we must have a corrupted chain.
		 */
		if( ptr )
		{
			if(ptr < oldptr )
			{
				malloc_errno = M_CODE_CHAIN_BROKE;
				malloc_fatal(func);
				return(NULL);
			}
			oldptr = ptr;
		}
		else if( oldptr != malloc_end )
		{
			/*
			 * This should never happen.  If it does, then
			 * we got a real problem.
			 */
			malloc_errno = M_CODE_NO_END;
			malloc_fatal(func);
			return(NULL);
		}
		

		/*
		 * if this element is already in use...
		 */
		if( ptr && ((ptr->flag & M_INUSE) != 0) )
		{
			continue;
		}

		/*
		 * if there isn't room for this block..
		 */
		if( ptr && (ptr->s.size < size) )
		{
			continue;
		}

		/*
		 * If ptr is null, we have run out of memory and must sbrk more
		 */
		if( ptr == NULL )
		{
			need = (size + M_SIZE) * (size > 100*1024 ? 1:2);
			if( need < M_BLOCKSIZE )
			{
				need = M_BLOCKSIZE;
			}
			else if( need & (M_BLOCKSIZE-1) )
			{
				need &= ~(M_BLOCKSIZE-1);
				need += M_BLOCKSIZE;
			}
			ptr = (struct mlist *) sbrk((int)need);
			if( ptr == (struct mlist *) -1 )
			{
				malloc_errno = M_CODE_NOMORE_MEM;
				malloc_fatal(func);
			}
			malloc_data_end = sbrk((int)0);

			ptr->prev   = oldptr;
			ptr->next   = (struct mlist *) 0;
			ptr->s.size = need - M_SIZE;
			ptr->flag  = M_MAGIC;

			oldptr->next = ptr;
			malloc_end = ptr;


		} /* if( ptr ==... */

		/*
	 	 * Now ptr points to a memory location that can store
		 * this data, so lets go to work.
		 */

		ptr->r_size = size;		/* save requested size	*/
		ptr->flag |= M_INUSE;

		/*
	 	 * split off unneeded data area in this block, if possible...
		 */
		malloc_split(ptr);

		/*
		 * re-adjust the requested size so that it is what the user
		 * actually requested...
		 */

		ptr->r_size--;

		/*
		 * just to make sure that noone is misusing malloced
	 	 * memory without initializing it, lets set it to
		 * all '\01's.  We call local_memset() because memset()
		 * may be checking for malloc'd ptrs and this isn't
		 * a malloc'd ptr yet.
		 */
		malloc_memset(ptr->data,M_FILL,(int)ptr->s.size);

		return( ptr->data);

	} /* for(... */

} /* malloc(... */

/*
 * Function:	malloc_split()
 *
 * Purpose:	to split a malloc segment if there is enough room at the
 *		end of the segment that isn't being used
 *
 * Arguments:	ptr	- pointer to segment to split
 *
 * Returns:	nothing of any use.
 *
 * Narrative:
 *		get the needed size of the module
 * 		round the size up to appropriat boundry
 *		calculate amount of left over space
 *		if there is enough left over space
 *		    create new malloc block out of remainder
 *		    if next block is free 
 *			join the two blocks together
 *		    fill new empty block with free space filler
 * 		    re-adjust pointers and size of current malloc block
 *		
 *		
 *
 * Mod History:	
 *   90/01/27	cpcahil		Initial revision.
 */
void
malloc_split(ptr)
	struct mlist		* ptr;
{
	extern struct mlist	* malloc_end;
	void			  malloc_join();
	void			  malloc_memset();
	int			  rest;
	int			  size;
	struct mlist		* tptr;

	size = ptr->r_size;

	/*
	 * roundup size to the appropriate boundry
	 */

	M_ROUNDUP(size);

	/*
	 * figure out how much room is left in the array.
	 * if there is enough room, create a new mlist 
	 *     structure there.
	 */

	if( ptr->s.size > size )
	{
		rest = ptr->s.size - size;
	}
	else
	{
		rest = 0;
	}
	
	if( rest > (M_SIZE+M_RND) )
	{
		tptr = (struct mlist *) (ptr->data+size);
		tptr->prev = ptr;
		tptr->next = ptr->next;
		tptr->flag = M_MAGIC;
		tptr->s.size = rest - M_SIZE;

		/*
		 * If possible, join this segment with the next one
		 */

		malloc_join(tptr, tptr->next,0,0);

		if( tptr->next )
		{
			tptr->next->prev = tptr;
		}

		malloc_memset(tptr->data,M_FREE_FILL, (int)tptr->s.size);

		ptr->next = tptr;
		ptr->s.size = size;

		if( malloc_end == ptr )
		{
			malloc_end = tptr;
		}
	}

} /* malloc_split(... */

/*
 * Function:	malloc_join()
 *
 * Purpose:	to join two malloc segments together (if possible)
 *
 * Arguments:	ptr	- pointer to segment to join to.
 * 		nextptr	- pointer to next segment to join to ptr.
 *
 * Returns:	nothing of any values.
 *
 * Narrative:
 *
 * Mod History:	
 *   90/01/27	cpcahil		Initial revision.
 */
void
malloc_join(ptr,nextptr, inuse_override, fill_flag)
	struct mlist	* ptr;
	struct mlist	* nextptr;
	int		  inuse_override;
	int		  fill_flag;
{
	unsigned int	  newsize;

	if( 	ptr     && ! (inuse_override || (ptr->flag & M_INUSE)) && 
		nextptr && ! (nextptr->flag & M_INUSE) &&
		((ptr->data+ptr->s.size) == (char *) nextptr) )
	{
		if( malloc_end == nextptr )
		{
			malloc_end = ptr;
		}
		ptr->next = nextptr->next;
		newsize = nextptr->s.size + M_SIZE;

		/*
		 * if we are to fill and this segment is in use,
		 *   fill in with M_FILL newly added space...
	 	 */

		if(fill_flag && (ptr->flag & M_INUSE) )
		{
			malloc_memset(ptr->data+ptr->s.size,
				      M_FILL, (int)(nextptr->s.size + M_SIZE));
		}

		ptr->s.size += newsize;
		if( ptr->next )
		{
			ptr->next->prev = ptr;
		}
	}

} /* malloc_join(... */


/*
 * The following mess is just to ensure that the versions of these functions in
 * the current library are included (to make sure that we don't accidentaly get 
 * the libc versions. (This is the lazy man's -u ld directive)
 */

void free();
int strcmp();
int memcmp();
char	* realloc();

void		(*malloc_void_funcs[])() =
{
	free,
};

int		(*malloc_int_funcs[])() =
{
	strcmp,
	memcmp,
};

char		* (*malloc_char_star_funcs[])() =
{
	realloc,
};

/*
 * This is malloc's own memset which is used without checking the parameters.
 */

void
malloc_memset(ptr,byte,len)
	char		* ptr;
	char		  byte;
	int		  len;
{

	while(len-- > 0)
	{
		*ptr++ = byte;
	}

} /* malloc_memset(... */

/*
 * Function:	malloc_fatal()
 *
 * Purpose:	to display fatal error message and take approrpriate action
 *
 * Arguments:	funcname - name of function calling this routine
 *
 * Returns:	nothing of any value
 *
 * Narrative:
 *
 * Notes:	This routine does not make use of any libc functions to build
 *		and/or disply the error message.  This is due to the fact that
 *		we are probably at a point where malloc is having a real problem
 *		and we don't want to call any function that may use malloc.
 */
void
malloc_fatal(funcname)
	char		* funcname;
{
	char		  errbuf[128];
	void		  exit();
	void		  malloc_err_handler();
	extern char	* malloc_err_strings[];
	extern int	  malloc_errno;
	extern int	  malloc_fatal_level;
	char		* s;
	char		* t;

	s = errbuf;
	t = "Fatal error: ";
	while( *s = *t++)
	{
		s++;
	}
	t = funcname;
	while( *s = *t++)
	{
		s++;
	}

	t = "(): ";
	while( *s = *t++)
	{
		s++;
	}

	t = malloc_err_strings[malloc_errno];
	while( *s = *t++)
	{
		s++;
	}

	*(s++) = '\n';

	if( write(malloc_errfd,errbuf,(unsigned)(s-errbuf)) != (s-errbuf))
	{
		(void) write(2,"I/O error to error file\n",(unsigned)24);
		exit(110);
	}
	malloc_err_handler(malloc_fatal_level);

} /* malloc_fatal(... */

/*
 * Function:	malloc_warning()
 *
 * Purpose:	to display warning error message and take approrpriate action
 *
 * Arguments:	funcname - name of function calling this routine
 *
 * Returns:	nothing of any value
 *
 * Narrative:
 *
 * Notes:	This routine does not make use of any libc functions to build
 *		and/or disply the error message.  This is due to the fact that
 *		we are probably at a point where malloc is having a real problem
 *		and we don't want to call any function that may use malloc.
 */
void
malloc_warning(funcname)
	char		* funcname;
{
	char		  errbuf[128];
	void		  exit();
	void		  malloc_err_handler();
	extern char	* malloc_err_strings[];
	extern int	  malloc_errno;
	extern int	  malloc_warn_level;
	char		* s;
	char		* t;

	s = errbuf;
	t = "Warning: ";
	while( *s = *t++)
	{
		s++;
	}
	t = funcname;
	while( *s = *t++)
	{
		s++;
	}

	t = "(): ";
	while( *s = *t++)
	{
		s++;
	}

	t = malloc_err_strings[malloc_errno];
	while( *s = *t++)
	{
		s++;
	}

	*(s++) = '\n';

	if( write(malloc_errfd,errbuf,(unsigned)(s-errbuf)) != (s-errbuf))
	{
		(void) write(2,"I/O error to error file\n",(unsigned)24);
		exit(110);
	}

	malloc_err_handler(malloc_warn_level);

} /* malloc_warning(... */

/*
 * Function:	malloc_err_handler()
 *
 * Purpose:	to take the appropriate action for warning and/or fatal 
 *		error conditions.
 *
 * Arguments:	level - error handling level 
 *
 * Returns:	nothing of any value
 *
 * Narrative:
 *
 * Notes:	This routine does not make use of any libc functions to build
 *		and/or disply the error message.  This is due to the fact that
 *		we are probably at a point where malloc is having a real problem
 *		and we don't want to call any function that may use malloc.
 */
void
malloc_err_handler(level)
{
	void		  exit();
	void		  malloc_dump();
	extern int	  malloc_errfd;

	if( level & M_HANDLE_DUMP )
	{
		malloc_dump(malloc_errfd);
	}

	switch( level & ~M_HANDLE_DUMP )
	{
		/*
		 * If we are to drop a core file and exit
		 */
		case M_HANDLE_ABORT:
			(void) abort();
			break;

		/*
		 * If we are to exit..
		 */
		case M_HANDLE_EXIT:
			exit(200);
			break;

		/*
		 * If we are to dump a core, but keep going on our merry way
		 */
		case M_HANDLE_CORE:
			{
				int	  pid;

				/*
				 * fork so child can abort (and dump core)
				 */
				if( (pid = fork()) == 0 )
				{
					(void) write(2,"Child dumping core\n",
							(unsigned)9);
					(void) abort();
				}

				/*
 				 * wait for child to finish dumping core
				 */
				while( wait((int *)0) != pid)
				{
				}

				/*
				 * Move core file to core.pid.cnt so 
				 * multiple cores don't overwrite each
				 * other.
				 */
				if( access("core",0) == 0 )
				{
					static int	  corecnt;
					char	  	  filenam[32];
					filenam[0] = 'c';
					filenam[1] = 'o';
					filenam[2] = 'r';
					filenam[3] = 'e';
					filenam[4] = '.';
					(void)tostring(filenam+5,getpid(),
						5, B_DEC, '0');
					filenam[10] = '.';
					(void)tostring(filenam+11,corecnt++,
						3, B_DEC, '0');
					filenam[14] = '\0';
					(void) unlink(filenam);
					if( link("core",filenam) == 0)
					{
						(void) unlink("core");
					}
				}
			}


		/* 
		 * If we are to just ignore the error and keep on processing
		 */
		case M_HANDLE_IGNORE:
			break;

	} /* switch(... */

} /* malloc_err_handler(... */

/*
 * $Log:	malloc.c,v $
 * Revision 1.6  90/05/11  00:13:09  cpcahil
 * added copyright statment
 * 
 * Revision 1.5  90/02/25  11:01:18  cpcahil
 * added support for malloc chain checking.
 * 
 * Revision 1.4  90/02/24  21:50:21  cpcahil
 * lots of lint fixes
 * 
 * Revision 1.3  90/02/24  14:51:18  cpcahil
 * 1. changed malloc_fatal and malloc_warn to use malloc_errno and be passed
 *    the function name as a parameter.
 * 2. Added several function headers.
 * 3. Changed uses of malloc_fatal/warning to conform to new usage.
 * 
 * Revision 1.2  90/02/23  18:05:23  cpcahil
 * fixed open of error log to use append mode.
 * 
 * Revision 1.1  90/02/22  23:17:43  cpcahil
 * Initial revision
 * 
 */