How to initialize this array of structures of array of structures?

Question

I have the following code, which is not working as expected. It compiles, but throws a lot of warnings and segfaults when executed:

#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;
}

I am probably initializing languages the wrong way.

• I would like to have that languages array in which I can access different dictionaries by language: languages[ONE]
• I would like to access then different translation tables with the dictionary field: languages[ONE].foo
• All translation tables accessed with a language+field pair may have different array lengths, as shown in the code example

Is that even possible? What am I doing wrong?

When compiling with gcc I get this (cropped) output:

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]

[...]

The same warnings/notes repeat for multiple parts of the code.

Answer 1

Here are two things you can do:

1. Allocate memory for struct translation *foo; and struct translation *bar; (you can also use malloc to dynamically allocate memory). For example:

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

2. Use a compound literal in your definition:

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},
            },
    },
};

Note

As mentioned by @M.M, adding the qualifier const before struct dictionary is a good idea if its values won't change during runtime.

Answer 2

Just initialize each array separately:

#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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