如何初始化这个结构数组结构数组？

Question

我有以下代码，它没有按预期工作。 它编译，但执行时会抛出很多警告和段错误：

#include <stdio.h>

enum output {
    A,
    B,
    C,
    D,
};

struct translation {
    char *from;
    enum output to;
};

struct dictionary {
    struct translation *foo;
    struct translation *bar;
};

enum language {
    ONE,
    ANOTHER,
};

struct dictionary languages[] = {
        [ONE] = {
                .foo = {
                        {"LF", A},
                        {"LLF", C},
                        {"RRF", D},
                },
                .bar = {
                        {"L", B},
                },
        },
        [ANOTHER] = {
                .foo = {
                        {"FF", B},
                        {"RRF", D},
                },
                .bar = {
                        {"LF", B},
                        {"R", C},
                        {"RR", D},
                },
        },
};

int main(void)
{
        printf("%s\n", languages[ONE].foo[0].from);
        return 0;
}

我可能错误地初始化languages 。

• 我希望有一个languages数组，我可以通过language访问不同的词典： languages[ONE]
• 我想使用字典字段访问不同的翻译表： languages[ONE].foo
• 使用语言+字段对访问的所有转换表可能具有不同的数组长度，如代码示例中所示

这甚至可能吗？ 我究竟做错了什么？

当用gcc编译时，我得到这个（裁剪的）输出：

asdf.c:27:17: warning: braces around scalar initializer
                 .foo = {
                 ^
asdf.c:27:17: note: (near initialization for ‘languages[0].foo’)
asdf.c:28:25: warning: braces around scalar initializer
                         {"LF", A},
                         ^
asdf.c:28:25: note: (near initialization for ‘languages[0].foo’)
asdf.c:28:26: warning: initialization of ‘struct translation *’ from incompatible pointer type ‘char *’ [-Wincompatible-pointer-types]

[...]

对于代码的多个部分，重复相同的警告/注释。

Answer 1

您可以执行以下两项操作：

1. 为struct translation *foo;分配内存struct translation *foo; 和struct translation *bar; （您也可以使用malloc动态分配内存）。 例如：

struct dictionary
{
    struct translation foo[10];
    struct translation bar[10];
};

2. 在定义中使用复合文字：

struct dictionary languages[] = {
    [ONE] = {
            .foo = (struct translation []){
                    {"LF", A},
                    {"LLF", C},
                    {"RRF", D},
            },
            .bar = (struct translation []){
                    {"L", B},
            },
    },
    [ANOTHER] = {
            .foo = (struct translation []){
                    {"FF", B},
                    {"RRF", D},
            },
            .bar = (struct translation []){
                    {"LF", B},
                    {"R", C},
                    {"RR", D},
            },
    },
};

注意

正如@MM所提到的，如果在运行时它的值不会改变，那么在struct dictionary之前添加限定符const是个好主意。

Answer 2

只需分别初始化每个数组：

#include <stdio.h>

enum output
{
    a
,   b
,   c
,   d
};

struct translation
{
    char const * from;
    enum output  to;
};

struct dictionary
{
    struct translation * foo;
    struct translation * bar;
};

enum language
{
    one
,   another
,   languages_count
};

struct translation one_language_foo_translations[] =
{
    {"LF" , a}
,   {"LLF", c}
,   {"RRF", d}
};

struct translation one_language_bar_translations[] =
{
    {"L", b}
};

struct translation another_language_foo_translations[] =
{
    {"FF" , b}
,   {"RRF", d}
};

struct translation another_language_bar_translations[] =
{
    {"LF", b}
,   {"R" , c}
,   {"RR", d}
};

struct dictionary languages[languages_count] =
{
    {one_language_foo_translations, one_language_bar_translations}
,   {another_language_foo_translations, another_language_bar_translations}
};

int main(void)
{
    printf("%s\n", languages[one].foo[0].from);
    return 0;
}

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