{"id":868,"date":"2026-05-15T15:24:34","date_gmt":"2026-05-15T07:24:34","guid":{"rendered":"https:\/\/hsiang.cc\/?p=868"},"modified":"2026-05-13T15:30:59","modified_gmt":"2026-05-13T07:30:59","slug":"c-%e7%9a%84%e9%82%a3%e4%ba%9b%e7%9c%89%e8%a7%92malloc-%e4%b9%8b%e5%be%8c%e4%b8%80%e5%ae%9a%e8%a6%81%e6%aa%a2%e6%9f%a5-%e8%a8%98%e6%86%b6%e9%ab%94%e9%85%8d%e7%bd%ae%e7%9a%84%e9%98%b2","status":"publish","type":"post","link":"https:\/\/hsiang.cc\/?p=868","title":{"rendered":"[C \u7684\u90a3\u4e9b\u7709\u89d2]malloc \u4e4b\u5f8c\u4e00\u5b9a\u8981\u6aa2\u67e5 \u2014 \u8a18\u61b6\u9ad4\u914d\u7f6e\u7684\u9632\u79a6\u6027\u5beb\u6cd5"},"content":{"rendered":"

\u5e73\u5e38\u5728\u5d4c\u5165\u5f0f\u7cfb\u7d71\u4e0a\u7528 malloc<\/code>\uff0c
\n\u5beb\u5b8c\u4e4b\u5f8c\u89ba\u5f97\u5f88\u723d\uff0c\u52d5\u614b\u914d\u7f6e\u8a18\u61b6\u9ad4\uff0c\u597d\u50cf\u5f88\u53b2\u5bb3\u3002<\/p>\n

uint8_t *buf = malloc(1024);\nmemset(buf, 0, 1024);\n\/\/ \u958b\u59cb\u7528 buf...<\/code><\/pre>\n
\u6709\u4e00\u6b21\u670b\u53cb\u770b\u4e86\u4e00\u773c\u554f\u6211\uff1a\u300cmalloc<\/code> \u5931\u6557\u600e\u9ebc\u8fa6\uff1f\u300d<\/p>\n
\u6211\u8aaa\uff1a\u300c\u6703\u5931\u6557\u55ce\uff1f\u8a18\u61b6\u9ad4\u61c9\u8a72\u5920\u5427\uff1f\u300d<\/p>\n
\u4ed6\u8aaa\uff1a\u300c\u5d4c\u5165\u5f0f\u7684 heap \u5c31\u90a3\u9ebc\u5927\uff0c\u4f60\u78ba\u5b9a\u55ce\uff1f\u300d<\/p>\n
\u6211 ........ \u7576\u7136\u4e0d\u662f\u5f88\u78ba\u5b9a\u3002<\/p>\n
<\/p>\n
\n
malloc \u53ef\u80fd\u6703\u5931\u6557<\/h2>\n
\u9019\u4ef6\u4e8b\u5f88\u591a\u4eba\u77e5\u9053\uff0c\u4f46\u5beb\u7a0b\u5f0f\u7684\u7576\u4e0b\u5e38\u5e38\u53c8\u795e\u5947\u7684\u5fd8\u8a18\u3002<\/p>\n
malloc<\/code> \u5728\u4ee5\u4e0b\u60c5\u6cc1\u6703\u5931\u6557\uff0c\u56de\u50b3 NULL<\/code>\uff1a<\/p>\n
    \n
  • heap \u7a7a\u9593\u4e0d\u8db3<\/strong> \u2014 \u5d4c\u5165\u5f0f\u7cfb\u7d71\u7684 heap \u901a\u5e38\u53ea\u6709\u5e7e KB \u5230\u5e7e\u5341 KB<\/li>\n
  • heap \u788e\u7247\u5316<\/strong> \u2014 \u6709\u8db3\u5920\u7684\u7e3d\u7a7a\u9593\uff0c\u4f46\u6c92\u6709\u9023\u7e8c\u7684\u5927\u584a\u53ef\u4ee5\u5206\u914d<\/li>\n
  • \u8acb\u6c42\u592a\u5927<\/strong> \u2014 \u4e00\u6b21\u8981\u6c42\u8d85\u904e\u53ef\u7528\u7a7a\u9593<\/li>\n<\/ul>\n
    \/\/ malloc \u5931\u6557\u6642\u56de\u50b3 NULL\nuint8_t *buf = malloc(1024);\n\n\/\/ \u274c \u6c92\u6709\u6aa2\u67e5\uff0c\u76f4\u63a5\u7528\nmemset(buf, 0, 1024);  \/\/ buf \u662f NULL\uff0c\u9019\u88e1\u76f4\u63a5 crash<\/code><\/pre>\n
    \u5728 PC \u4e0a\uff0c\u8a18\u61b6\u9ad4\u901a\u5e38\u5f88\u5145\u88d5\uff0c
    \nmalloc<\/code> \u5931\u6557\u7684\u6a5f\u7387\u5f88\u4f4e\uff0c
    \n\u6240\u4ee5\u5f88\u591a\u4eba\u990a\u6210\u4e86\u4e0d\u6aa2\u67e5\u7684\u7fd2\u6163\u3002<\/p>\n
    \u5e36\u5230\u5d4c\u5165\u5f0f\uff0c\u5c31\u8e29\u5751\u4e86\u3002<\/p>\n
    \n
    \u57fa\u672c\u7684\u9632\u79a6\u5beb\u6cd5<\/h2>\n
    uint8_t *buf = malloc(1024);\nif (buf == NULL) {\n    \/\/ \u914d\u7f6e\u5931\u6557\uff0c\u8655\u7406\u932f\u8aa4\n    LOG_ERROR("malloc failed, size=%d", 1024);\n    return ERR_NO_MEMORY;\n}\n\n\/\/ \u78ba\u8a8d buf \u6709\u6548\u624d\u7e7c\u7e8c\nmemset(buf, 0, 1024);\n\/\/ ... \u4f7f\u7528 buf ...<\/code><\/pre>\n
    \u5c31\u9019\u6a23\uff0c\u591a\u4e09\u884c\uff0c\u4f46\u53ef\u4ee5\u6551\u4f60\u5f88\u591a\u6b21\u3002<\/p>\n
    \n
    \u5305\u88dd\u6210\u5b89\u5168\u7248\u672c<\/h2>\n
    \u6bcf\u6b21 malloc<\/code> \u90fd\u8981\u5beb\u4e00\u6a23\u7684\u6aa2\u67e5\uff0c\u5f88\u56c9\u55e6\u3002
    \n\u6211\u7fd2\u6163\u5305\u4e00\u500b wrapper\uff1a<\/p>\n
    \/\/ safe_malloc.h\n#include <stdlib.h>\n#include <string.h>\n\n\/**\n * \u914d\u7f6e\u8a18\u61b6\u9ad4\u4e26\u6e05\u96f6\uff0c\u5931\u6557\u6642\u56de\u50b3 NULL\n *\/\nstatic inline void *safe_malloc(size_t size) {\n    if (size == 0) {\n        return NULL;\n    }\n    void *ptr = malloc(size);\n    if (ptr != NULL) {\n        memset(ptr, 0, size);  \/\/ \u9806\u4fbf\u6e05\u96f6\uff0c\u907f\u514d\u5783\u573e\u503c\n    }\n    return ptr;\n}\n\n\/**\n * \u914d\u7f6e\u8a18\u61b6\u9ad4\uff0c\u5931\u6557\u6642\u5370 log \u4e26\u56de\u50b3 NULL\n *\/\n#define MALLOC_LOG(size)  malloc_with_log((size), __FILE__, __LINE__)\n\nstatic inline void *malloc_with_log(size_t size,\n                                     const char *file,\n                                     int line) {\n    void *ptr = malloc(size);\n    if (ptr == NULL) {\n        \/\/ \u4f60\u7684 log \u51fd\u5f0f\n        log_error("[%s:%d] malloc failed, size=%zu", file, line, size);\n    }\n    return ptr;\n}<\/code><\/pre>\n
    \u4f7f\u7528\uff1a<\/p>\n
    uint8_t *buf = safe_malloc(1024);\nif (buf == NULL) {\n    return ERR_NO_MEMORY;\n}<\/code><\/pre>\n
    \u6216\u662f\u60f3\u8981\u81ea\u52d5\u5e36 log\uff1a<\/p>\n
    uint8_t *buf = MALLOC_LOG(1024);\nif (buf == NULL) {\n    return ERR_NO_MEMORY;\n}<\/code><\/pre>\n
    \n
    calloc vs malloc<\/h2>\n
    \u5f88\u591a\u4eba\u53ea\u77e5\u9053 malloc<\/code>\uff0c\u4f46 calloc<\/code> \u5728\u67d0\u4e9b\u60c5\u6cc1\u66f4\u597d\u7528\uff1a<\/p>\n
    \/\/ malloc\uff1a\u914d\u7f6e\u8a18\u61b6\u9ad4\uff0c\u5167\u5bb9\u662f\u5783\u573e\u503c\nuint8_t *buf = malloc(1024);\n\n\/\/ calloc\uff1a\u914d\u7f6e\u8a18\u61b6\u9ad4\uff0c\u5167\u5bb9\u6e05\u96f6\n\/\/ calloc(\u5143\u7d20\u6578\u91cf, \u6bcf\u500b\u5143\u7d20\u5927\u5c0f)\nuint8_t *buf = calloc(1024, sizeof(uint8_t));<\/code><\/pre>\n
    calloc<\/code> \u5e6b\u4f60\u505a\u4e86\u6e05\u96f6\uff0c\u4e0d\u9700\u8981\u518d memset<\/code>\u3002<\/p>\n
    \u53e6\u5916\uff0ccalloc<\/code> \u5728\u8a08\u7b97\u7e3d\u5927\u5c0f\u7684\u6642\u5019\uff0c
    \n\u6703\u5e6b\u4f60\u505a\u6ea2\u4f4d\u6aa2\u67e5\uff1a<\/p>\n
    \/\/ \u5982\u679c count * size \u6ea2\u4f4d\uff0cmalloc \u53ef\u80fd\u914d\u7f6e\u5230\u932f\u8aa4\u5927\u5c0f\u7684\u8a18\u61b6\u9ad4\nsize_t count = 1000000;\nsize_t size  = 10000;\nuint8_t *buf = malloc(count * size);  \/\/ count * size \u53ef\u80fd\u6ea2\u4f4d\uff01\n\n\/\/ calloc \u6703\u5728\u5167\u90e8\u6aa2\u67e5\uff0c\u6ea2\u4f4d\u6642\u56de\u50b3 NULL\nuint8_t *buf = calloc(count, size);  \/\/ \u5b89\u5168<\/code><\/pre>\n
    \u6211\u7684\u7fd2\u6163\uff1a<\/p>\n