结构体的正确内存分配

发布于 2024-12-20 07:36:00 字数 516 浏览 2 评论 0原文

以这种方式定义一个结构体，我需要分配内存

typedef struct string_collection {
    char **c;
    size_t current, allocated;
} TSC, *ASC;

所以我带着这段代码，这是正确的还是我错过了一些东西？首先分配结构描述符，然后为指向字符串的 d 指针分配足够的空间

ASC AlocSC(size_t d)
{
    ASC sc;

    sc = (TSC*) malloc(sizeof(TSC));
    if (!sc) return NULL;

    sc->c = calloc(d, sizeof(char *));

    if (!sc->c) {
        free(sc);
        return NULL;
    }

    sc->current = 0;
    sc->allocated = d;

    return sc;
}

原文

Having a struct defined in a such way, I need to allocate memory

typedef struct string_collection {
    char **c;
    size_t current, allocated;
} TSC, *ASC;

So I came with this code, is it right or I missed something? First allocating struct descriptor and then enough space for d pointers to string

ASC AlocSC(size_t d)
{
    ASC sc;

    sc = (TSC*) malloc(sizeof(TSC));
    if (!sc) return NULL;

    sc->c = calloc(d, sizeof(char *));

    if (!sc->c) {
        free(sc);
        return NULL;
    }

    sc->current = 0;
    sc->allocated = d;

    return sc;
}

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请远离我 2024-12-27 07:36:00

编辑的代码本质上是正确的，尽管我与您有一些风格上的差异（例如不执行 typedef 来隐藏对象的“指针”，不使用 malloc/calloc 调用中分配的对象的大小，以及其他一些东西）。

您的代码“清理”了一下：

TSC *AlocSC(size_t d)
{
    TSC *sc = malloc(sizeof *sc);
    if (!sc) return NULL;

    sc->c = calloc(d, sizeof *sc->c);
    if (!sc->c) {
        free(sc);
        return NULL;
    }

    sc->current = 0;
    sc->allocated = d;

    return sc;
}

The code as edited is essentially correct, though I have several stylistic differences with you (such as not doing a typedef to hide the "pointerness" of an object, not using the size of the allocated object in the malloc/calloc call, and a few other things).

Your code, "cleaned up" a bit:

TSC *AlocSC(size_t d)
{
    TSC *sc = malloc(sizeof *sc);
    if (!sc) return NULL;

    sc->c = calloc(d, sizeof *sc->c);
    if (!sc->c) {
        free(sc);
        return NULL;
    }

    sc->current = 0;
    sc->allocated = d;

    return sc;
}

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春夜浅 2024-12-27 07:36:00

只要将 x 替换为 sc，在我看来就可以了。但是，您不应该在 C 中强制转换 malloc 的返回值（了解更多信息此处）。我会改为使用该行：

sc = malloc(sizeof(*sc));

您可以对 x->c 指向 (char*) 的类型的大小执行相同的操作。

As long as x is replaced with sc, it looks ok to me. You shouldn't, however, cast the return of malloc in C (read more here). I would instead have for that line: