指定初始化數組

Question

的陣列我們大概知道C99 designated initializers，它們可以被用來初始化大常量數組的方式：

const int vals[] = { 
    [0] = 10, 
    [10] = 12 
} 

哪個initalizes的vals指數0到10和vals到12指數10 。

我的問題是如何使用這種風格的指定初始化器陣列的數組。這裏是我的示例代碼：

typedef enum { 
    COMMON = 0, 
    STRINGS, 
    KEY, 
    PRECUSSIVE, 
    GUITAR, 
    KEYBOARD, 
    BASS, 
    PIANO, 
    DRUMS, 
    _INST_MAX 
} instrument_classification_t; 
    static const int * const instrument_class_hierarchy[] = { 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
    [STRINGS] = {GUITAR, BASS, _INST_MAX}, 
    [KEY] = {PIANO, KEYBOARD, _INST_MAX}, 
    [PRECUSSIVE] = {DRUMS, _INST_MAX}, 
    [GUITAR] = NULL, 
    [KEYBOARD] = NULL, 
    [BASS] = NULL, 
    [PIANO] = NULL, 
    [DRUMS] = NULL 
}; 

但我得到這些警告，這意味着初始化只使用第一個元素。

main.c:166:3: warning: braces around scalar initializer 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
^
main.c:166:3: note: (near initialization for 'instrument_class_hierarchy[0]') 
main.c:166:15: warning: initialization makes pointer from integer without a cast [-Wint-conversion] 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
     ^
main.c:166:15: note: (near initialization for 'instrument_class_hierarchy[0]') 
main.c:166:24: warning: excess elements in scalar initializer 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
        ^
main.c:166:24: note: (near initialization for 'instrument_class_hierarchy[0]') 
main.c:166:29: warning: excess elements in scalar initializer 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
         ^
main.c:166:29: note: (near initialization for 'instrument_class_hierarchy[0]') 
main.c:166:41: warning: excess elements in scalar initializer 
    [COMMON] = {STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 
            ^
main.c:166:41: note: (near initialization for 'instrument_class_hierarchy[0]') 
main.c:167:3: warning: braces around scalar initializer 
    [STRINGS] = {GUITAR, BASS, _INST_MAX}, 
^
main.c:167:3: note: (near initialization for 'instrument_class_hierarchy[1]') 
main.c:167:16: warning: initialization makes pointer from integer without a cast [-Wint-conversion] 
    [STRINGS] = {GUITAR, BASS, _INST_MAX}, 
      ^
main.c:167:16: note: (near initialization for 'instrument_class_hierarchy[1]') 
main.c:167:24: warning: excess elements in scalar initializer 
    [STRINGS] = {GUITAR, BASS, _INST_MAX}, 
        ^
main.c:167:24: note: (near initialization for 'instrument_class_hierarchy[1]') 
main.c:167:30: warning: excess elements in scalar initializer 
    [STRINGS] = {GUITAR, BASS, _INST_MAX}, 
         ^
main.c:167:30: note: (near initialization for 'instrument_class_hierarchy[1]') 
main.c:168:3: warning: braces around scalar initializer 
    [KEY] = {PIANO, KEYBOARD, _INST_MAX}, 
^
main.c:168:3: note: (near initialization for 'instrument_class_hierarchy[2]') 
main.c:168:12: warning: initialization makes pointer from integer without a cast [-Wint-conversion] 
    [KEY] = {PIANO, KEYBOARD, _INST_MAX}, 
     ^
main.c:168:12: note: (near initialization for 'instrument_class_hierarchy[2]') 
main.c:168:19: warning: excess elements in scalar initializer 
    [KEY] = {PIANO, KEYBOARD, _INST_MAX}, 
      ^
main.c:168:19: note: (near initialization for 'instrument_class_hierarchy[2]') 
main.c:168:29: warning: excess elements in scalar initializer 
    [KEY] = {PIANO, KEYBOARD, _INST_MAX}, 
         ^
main.c:168:29: note: (near initialization for 'instrument_class_hierarchy[2]') 
main.c:169:3: warning: braces around scalar initializer 
    [PRECUSSIVE] = {DRUMS, _INST_MAX}, 
^
main.c:169:3: note: (near initialization for 'instrument_class_hierarchy[3]') 
main.c:169:19: warning: initialization makes pointer from integer without a cast [-Wint-conversion] 
    [PRECUSSIVE] = {DRUMS, _INST_MAX}, 
      ^
main.c:169:19: note: (near initialization for 'instrument_class_hierarchy[3]') 
main.c:169:26: warning: excess elements in scalar initializer 
    [PRECUSSIVE] = {DRUMS, _INST_MAX}, 

Answer 1

值的支撐列表無法初始化指針。你的錯誤是一樣的：

int *p = { 1, 2, 3 }; 

你可以使用一個複合文字來代替：

// ... 
[COMMON] = (const int[]){STRINGS, KEY, PRECUSSIVE, _INST_MAX}, 

這是假定該代碼是在文件範圍內（即在任何函數之外），這意味着複合文字具有靜態存儲時間，因此指向它們是安全的。如果你的代碼實際上在一個函數內，你需要聲明單獨的靜態數組或者做一些其他修改。