{"topic":{"id":13004,"title":"写 C 碰见的奇怪问题","slug":"topic","categoryId":14,"createdAt":"2024-07-04 15:17:22.789455","bumpedAt":"2024-07-04 17:29:16.745486","views":177,"postsCount":4,"highestPostNumber":4,"likeCount":2,"closed":true,"pinned":false,"excerpt":"我要在 CS61C 给的框架里写一个 C 语言的变长数组。因为学艺不精碰到了奇怪的问题.和 malloc free 有关. 在 67-73 行删除之后新建出来的数组里，在应该是 0 的地方会有奇怪的数字，比如 5 和 6. 请神通广大的门友救一救 🫠 提供一点思路或者 debug 方法也可以. 核心代码如下: struct vector_t { size_t size; int *data; }; vector_t *vector_n…","deletedAt":null,"isAnonymous":false,"category":{"id":14,"name":"问答","slug":"qa","color":"f5c211"},"author":{"id":1628,"username":"Lorange","name":"主治医师李大华","avatarUrl":"/uploads/image/f8/ec/f8ecbeb887c4a1311f4f0bf05928476c7b3f632d15bb2b24e782baf2ba6f0d71.avif"},"tags":[]},"posts":[{"id":36720,"postNumber":1,"raw":"我要在 CS61C 给的框架里写一个 C 语言的变长数组。因为学艺不精碰到了奇怪的问题.和 malloc free 有关.\n在 67-73 行删除之后新建出来的数组里，在应该是 0 的地方会有奇怪的数字，比如 5 和 6.\n请神通广大的门友救一救 :melt:\n提供一点思路或者 debug 方法也可以.\n\n核心代码如下:\n```\nstruct vector_t {\n size_t size;\n int *data;\n};\n\n vector_t *vector_new() {\n vector_t *retval;\n retval = malloc(sizeof(vector_t));\n if (retval==NULL) {\n allocation_failed();\n }\n\n retval->size = 1;\n retval->data = malloc(sizeof(int));\n\n\n if (retval->data==NULL) {\n free(retval);\t\n allocation_failed();\n }\n retval->data[0]= 0;\n\n return retval;\n} \n\nvoid vector_delete(vector_t *v) {\n if(v!=NULL&&v->data!=NULL){\n for(int i =0;isize;i++){\n v->data[i]=0;\n }\n free(v->data);\n v->data=NULL;\n v->size=0;\n free(v);\n }\n}\nvoid vector_set(vector_t *v, size_t loc, int value) {\n\n if(loc>v->size){\n int i =0;\n int size = loc+1;\n int *temp = malloc(size*sizeof(int));\n v->size=size;\n\n for(i=0;idata[i];\n }\n else{\n temp[i]=0;\n }\n }\n temp[loc]=value;\n free(v->data);\n v->data=temp;\n \n }else{\n v->data[loc]=value;\n }\n for (int i = 0; i < 20; i++)\n {\n printf(\"%d \",v->data[i]);\n }\n printf(\"\\n\");\n \n}\nint main(int argc, char **argv) {\n vector_t *v;\n\n printf(\"Calling vector_new()\\n\");\n v = vector_new();\n\n printf(\"Calling vector_delete()\\n\");\n vector_delete(v);\n\n printf(\"vector_new() again\\n\");\n v = vector_new();\n\n printf(\"These should all return 0 (vector_get()): \");\n printf(\"%d \", vector_get(v, 0));\n printf(\"%d \", vector_get(v, 1));\n printf(\"%d\\n\", vector_get(v, 2));\n\n printf(\"Doing a bunch of vector_set()s\\n\");\n vector_set(v, 0, 98);\n vector_set(v, 11, 15);\n vector_set(v, 15, -23);\n vector_set(v, 24, 65);\n vector_set(v, 500, 3);\n vector_set(v, 12, -123);\n vector_set(v, 15, 21);\n vector_set(v, 25, 43);\n\n\n printf(\"These should be equal:\\n\");\n printf(\"98 = %d\\n\", vector_get(v, 0));\n printf(\"15 = %d\\n\", vector_get(v, 11));\n printf(\"65 = %d\\n\", vector_get(v, 24));\n printf(\"-123 = %d\\n\", vector_get(v, 12));\n printf(\"21 = %d\\n\", vector_get(v, 15));\n printf(\"43 = %d\\n\", vector_get(v, 25));\n printf(\"0 = %d\\n\", vector_get(v, 23));\n printf(\"0 = %d\\n\", vector_get(v, 1));\n printf(\"0 = %d\\n\", vector_get(v, 501));\n printf(\"3 = %d\\n\", vector_get(v, 500));\n\n vector_delete(v);\n\n printf(\"Test complete.\\n\");\n\n return 0;\n}\n```","cooked":"

我要在 CS61C 给的框架里写一个 C 语言的变长数组。因为学艺不精碰到了奇怪的问题.和 malloc free 有关.
\n在 67-73 行删除之后新建出来的数组里，在应该是 0 的地方会有奇怪的数字，比如 5 和 6.
\n请神通广大的门友救一救 🫠
\n提供一点思路或者 debug 方法也可以.

核心代码如下:

struct vector_t {\n    size_t size;\n    int *data;\n};\n\n    vector_t *vector_new() {\n    vector_t *retval;\n    retval = malloc(sizeof(vector_t));\n    if (retval==NULL) {\n        allocation_failed();\n    }\n\n    retval->size = 1;\n    retval->data = malloc(sizeof(int));\n\n\n    if (retval->data==NULL) {\n        free(retval);\t\n        allocation_failed();\n    }\n    retval->data[0]= 0;\n\n    return retval;\n} \n\nvoid vector_delete(vector_t *v) {\n    if(v!=NULL&&v->data!=NULL){\n        for(int i =0;i<v->size;i++){\n            v->data[i]=0;\n        }\n        free(v->data);\n        v->data=NULL;\n        v->size=0;\n        free(v);\n    }\n}\nvoid vector_set(vector_t *v, size_t loc, int value) {\n\n    if(loc>v->size){\n        int i =0;\n        int size = loc+1;\n        int *temp = malloc(size*sizeof(int));\n        v->size=size;\n\n        for(i=0;i<size;i++){\n            if(i<size-1)\n            {\n                temp[i]=v->data[i];\n            }\n            else{\n                temp[i]=0;\n            }\n        }\n        temp[loc]=value;\n        free(v->data);\n        v->data=temp;\n        \n    }else{\n        v->data[loc]=value;\n    }\n    for (int i = 0; i < 20; i++)\n    {\n        printf(\"%d \",v->data[i]);\n    }\n    printf(\"\\n\");\n    \n}\nint main(int argc, char **argv) {\n    vector_t *v;\n\n    printf(\"Calling vector_new()\\n\");\n    v = vector_new();\n\n    printf(\"Calling vector_delete()\\n\");\n    vector_delete(v);\n\n    printf(\"vector_new() again\\n\");\n    v = vector_new();\n\n    printf(\"These should all return 0 (vector_get()): \");\n    printf(\"%d \", vector_get(v, 0));\n    printf(\"%d \", vector_get(v, 1));\n    printf(\"%d\\n\", vector_get(v, 2));\n\n    printf(\"Doing a bunch of vector_set()s\\n\");\n    vector_set(v, 0, 98);\n    vector_set(v, 11, 15);\n    vector_set(v, 15, -23);\n    vector_set(v, 24, 65);\n    vector_set(v, 500, 3);\n    vector_set(v, 12, -123);\n    vector_set(v, 15, 21);\n    vector_set(v, 25, 43);\n\n\n    printf(\"These should be equal:\\n\");\n    printf(\"98 = %d\\n\", vector_get(v, 0));\n    printf(\"15 = %d\\n\", vector_get(v, 11));\n    printf(\"65 = %d\\n\", vector_get(v, 24));\n    printf(\"-123 = %d\\n\", vector_get(v, 12));\n    printf(\"21 = %d\\n\", vector_get(v, 15));\n    printf(\"43 = %d\\n\", vector_get(v, 25));\n    printf(\"0 = %d\\n\", vector_get(v, 23));\n    printf(\"0 = %d\\n\", vector_get(v, 1));\n    printf(\"0 = %d\\n\", vector_get(v, 501));\n    printf(\"3 = %d\\n\", vector_get(v, 500));\n\n    vector_delete(v);\n\n    printf(\"Test complete.\\n\");\n\n    return 0;\n}\n

\n","createdAt":"2024-07-04 15:17:22.876709","updatedAt":"2024-07-04 16:53:13.17168","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":348,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":5,"publicVersion":5,"deletedAt":null,"isAnonymous":false,"user":{"id":1628,"username":"Lorange","name":"主治医师李大华","avatarUrl":"/uploads/image/f8/ec/f8ecbeb887c4a1311f4f0bf05928476c7b3f632d15bb2b24e782baf2ba6f0d71.avif","admin":false,"moderator":true,"signatureRaw":null,"signatureCooked":null}},{"id":36721,"postNumber":2,"raw":"说实话，我写 c 还没到见 vector_t 的程度。。。。","cooked":"

说实话，我写 c 还没到见 vector_t 的程度。。。。

\n","createdAt":"2024-07-04 15:20:28.550349","updatedAt":"2024-07-04 15:20:28.550349","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":16,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":178,"username":"Hypocrisy","name":"rotartsinimdA","avatarUrl":"/uploads/image/ce/f3/cef3773e378e161524cc7523c8a63dff0698d22802b0c1ab669894d395ee36a3.avif","admin":false,"moderator":true,"signatureRaw":null,"signatureCooked":null}},{"id":36727,"postNumber":3,"raw":"![image|690x388](/uploads/image/a2/30/a230e457f1e6d064fdc859c5a2e3c7697c5c986f63b2773eeb93801c1c05ad5e.avif)\n\n这是最后打印出来的数组的样子","cooked":"

$\"image\"$

这是最后打印出来的数组的样子

\n","createdAt":"2024-07-04 16:54:59.33571","updatedAt":"2024-07-04 16:58:23.574254","replyToPostNumber":null,"replyCount":0,"likeCount":0,"wordCount":15,"liked":false,"bookmarked":false,"polls":[],"reactions":[],"wiki":false,"version":1,"publicVersion":1,"deletedAt":null,"isAnonymous":false,"user":{"id":1628,"username":"Lorange","name":"主治医师李大华","avatarUrl":"/uploads/image/f8/ec/f8ecbeb887c4a1311f4f0bf05928476c7b3f632d15bb2b24e782baf2ba6f0d71.avif","admin":false,"moderator":true,"signatureRaw":null,"signatureCooked":null}},{"id":36728,"postNumber":4,"raw":"为什么我删不掉帖子，答案是我将变量写反了，这个问题太蠢了","cooked":"

为什么我删不掉帖子，答案是我将变量写反了，这个问题太蠢了

\n","createdAt":"2024-07-04 17:26:27.320741","updatedAt":"2024-07-04 17:29:38.304947","replyToPostNumber":null,"replyCount":0,"likeCount":2,"wordCount":28,"liked":false,"bookmarked":false,"polls":[],"reactions":[{"reaction":"hugging_face_cat","count":2,"users":[{"id":431,"username":"anon10589529","name":null},{"id":2902,"username":"1313","name":"ᐕ)ﾉ"}],"hasReacted":false},{"reaction":"❤️","count":2,"users":[{"id":2902,"username":"1313","name":"ᐕ)ﾉ"},{"id":6205,"username":"uika_winwing","name":null}],"hasReacted":false}],"wiki":false,"version":3,"publicVersion":3,"deletedAt":null,"isAnonymous":false,"user":{"id":1628,"username":"Lorange","name":"主治医师李大华","avatarUrl":"/uploads/image/f8/ec/f8ecbeb887c4a1311f4f0bf05928476c7b3f632d15bb2b24e782baf2ba6f0d71.avif","admin":false,"moderator":true,"signatureRaw":null,"signatureCooked":null}}],"hasMore":false,"lastReadPostNumber":1,"hasUrlPostNumber":false}