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f56dd32bf7
Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
45 lines
1.4 KiB
C
45 lines
1.4 KiB
C
/* Copyright (C) 2000 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#ifndef _list_h_
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#define _list_h_
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct st_list {
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struct st_list *prev,*next;
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void *data;
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} LIST;
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typedef int (*list_walk_action)(void *,void *);
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extern LIST *list_add(LIST *root,LIST *element);
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extern LIST *list_delete(LIST *root,LIST *element);
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extern LIST *list_cons(void *data,LIST *root);
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extern LIST *list_reverse(LIST *root);
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extern void list_free(LIST *root,unsigned int free_data);
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extern unsigned int list_length(LIST *);
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extern int list_walk(LIST *,list_walk_action action,unsigned char * argument);
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#define list_rest(a) ((a)->next)
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#define list_push(a,b) (a)=list_cons((b),(a))
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#define list_pop(A) {LIST *old=(A); (A)=list_delete(old,old); my_free(old); }
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#ifdef __cplusplus
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}
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#endif
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#endif
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