Linux GNU C結構體陣列初始化示例
阿新 • • 發佈：2019-01-24
實然心血來潮，想學習一下結構體陣列的初始化方面的知識。
以下是GCC實然心血來潮，想學習一下結構體陣列的初始化方面的知識。特有的陣列初始化的風格：
// 陣列賦值另一種方式，但只在gcc下編譯通過，g++不能
enum {
AAA = 0,
BBB,
CCC,
DDD,
};
// 只對感興趣的索引值進行賦值，而不管下標的順序
static const int regs[] = {
[DDD] = 250,
[CCC] = 3,
[AAA] = 180,
};這種風格在kernel程式碼中經常看到。它不按照陣列下標順序，而是使用自定義的“索引”來賦值，比如Intel網絡卡igb驅動中一處程式碼：
從程式碼中可以清晰知道，這個結構體是針對82575的——board_82575比數字0更直觀易讀。static const struct e1000_info *igb_info_tbl[] = { [board_82575] = &e1000_82575_info, };
但是使用g++卻無法編譯，編譯錯誤提示如下：
sorry, unimplemented: non-trivial designated initializers not supported下面再看看結構體陣列的初始化，先給出結構體的定義：
enum control_type { TYPE_GPIO = 0, TYPE_IIC = 1, TYPE_SPI = 2, }; typedef struct control_info_t { const char *name; enum control_type type; int enable; }control_info;
初始化方式一，依次給陣列內元素賦值，如下：：
control_info control_info1[3] =
{
{"FOO_GPIO", TYPE_GPIO, 1},
{"FOO_IIC", TYPE_IIC, 0},
{"FOO_SPI", TYPE_SPI, 1},
};方式二，先宣告再賦值，如下：
方式三，不按照順序，只對感興趣幾項賦值，如下：control_info control_info[3]; control_info[TYPE_SPI].name = "FOO_SPI"; control_info[TYPE_SPI].type = TYPE_SPI; control_info[TYPE_SPI].enable = 1;
control_info control_info2[3] =
{
[TYPE_SPI] = {"FOO_SPI", TYPE_SPI, 1},
[TYPE_GPIO] = {"FOO_GPIO", TYPE_GPIO, 1},
};本文完整程式碼如下：
/**
結果：
struct test
250 0 180 3
111 name: FOO_IIC type: 1 enable: 0
222 name: FOO_GPIO type: 0 enable: 1
333 name: FOO_SPI type: 2 enable: 1
*/
#include <stdio.h>
#include <inttypes.h>
///////////////////////
// 簡單int型別的陣列
// 陣列賦值另一種方式，但只在gcc下編譯通過，g++不能
enum {
AAA = 0,
BBB,
CCC,
DDD,
};
// 只對感興趣的索引值進行賦值，而不管下標的順序
static const int regs[] = {
[DDD] = 250,
[CCC] = 3,
[AAA] = 180,
};
void struct_test1()
{
printf("%d %d %d %d\n", regs[DDD], regs[BBB], regs[AAA], regs[CCC]);
}
///////////////////////
// 結構體陣列初始化示例
enum control_type
{
TYPE_GPIO = 0,
TYPE_IIC = 1,
TYPE_SPI = 2,
};
typedef struct control_info_t {
const char *name;
enum control_type type;
int enable;
}control_info;
void struct_test_2()
{
// c++風格，用g++並使用 -std=c++11
//control_info gcontrol_info0 {.name = "FOO", .type = TYPE_SPI, .enable=1};
// 三個依次賦值
control_info control_info1[3] =
{
{"FOO_GPIO", TYPE_GPIO, 1},
{"FOO_IIC", TYPE_IIC, 0},
{"FOO_SPI", TYPE_SPI, 1},
};
printf("111 name: %s type: %d enable: %d\n", control_info1[TYPE_IIC].name, control_info1[TYPE_IIC].type, control_info1[TYPE_IIC].enable);
// GNU風格賦值
control_info control_info2[3] =
{
[TYPE_SPI] = {"FOO_SPI", TYPE_SPI, 1},
[TYPE_GPIO] = {"FOO_GPIO", TYPE_GPIO, 1},
};
printf("222 name: %s type: %d enable: %d\n", control_info2[TYPE_GPIO].name, control_info2[TYPE_GPIO].type, control_info2[TYPE_GPIO].enable);
// 只有一個賦值
control_info control_info[3];
control_info[TYPE_SPI].name = "FOO_SPI";
control_info[TYPE_SPI].type = TYPE_SPI;
control_info[TYPE_SPI].enable = 1;
printf("333 name: %s type: %d enable: %d\n", control_info[TYPE_SPI].name, control_info[TYPE_SPI].type, control_info[TYPE_SPI].enable);
}
int main(void)
{
printf("struct test\n");
struct_test1();
struct_test_2();
return 0;
}李遲 2016.10.13 週四 中午午休前