c - 为什么这段代码通过了编译器并成为验证码？

Question

以下是开源项目 X264 的代码片段，在尝试将其移植以支持 VS 编译器 cl.exe 时出现构建错误。 cl.exe 将 [X264_PULLDOWN_22] 视为 lambda 的开始。那么谁能解释一下这行在 C 语言中的含义。

typedef struct
{
    int mod;
    uint8_t pattern[24];
    float fps_factor;
} cli_pulldown_t;

enum pulldown_type_e
{
    X264_PULLDOWN_22 = 1,
    X264_PULLDOWN_32,
    X264_PULLDOWN_64,
    X264_PULLDOWN_DOUBLE,
    X264_PULLDOWN_TRIPLE,
    X264_PULLDOWN_EURO
};

#define TB  PIC_STRUCT_TOP_BOTTOM
#define BT  PIC_STRUCT_BOTTOM_TOP
#define TBT PIC_STRUCT_TOP_BOTTOM_TOP
#define BTB PIC_STRUCT_BOTTOM_TOP_BOTTOM

static const cli_pulldown_t pulldown_values[] =
{
    /*WHAT DOES THIS LINE MEAN???, how can you assign to [X264_PULLDOWN_22]*/
    [X264_PULLDOWN_22]     = {1,  {TB}, 1.0},
    [X264_PULLDOWN_32]     = {4,  {TBT, BT, BTB, TB},                     1.25},
    [X264_PULLDOWN_64]     = {2,  {PIC_STRUCT_DOUBLE, PIC_STRUCT_TRIPLE}, 1.0},
    [X264_PULLDOWN_DOUBLE] = {1,  {PIC_STRUCT_DOUBLE},                    2.0},
    [X264_PULLDOWN_TRIPLE] = {1,  {PIC_STRUCT_TRIPLE},                    3.0},
    [X264_PULLDOWN_EURO]   = {24, {TBT, BT, BT, BT, BT, BT, BT, BT, BT, BT, BT, BT,
                                   BTB, TB, TB, TB, TB, TB, TB, TB, TB, TB, TB, TB}, 25.0/24.0}
};

Answer 1

这就是所谓的指定初始化程序。您可以阅读更多相关信息 here .