CODEWITHSUNDEEP
c
ZijingWu
ZijingWu

Reputation: 3490

Why this code pass the compiler and be validate code?

Following is code snippet from the open source project X264, I got build error when try to port it to support VS compiler cl.exe. The cl.exe treat the [X264_PULLDOWN_22] as the begin of lambda. So can anybody explain what this line means in C language.

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}
};

Upvotes: 1

Views: 95

Answers (3)

Klas Lindbäck
Klas Lindbäck

Reputation: 33273

It's called a designated initializer and is a shorthand way to initialize variables.

How to fix your compilation problem:

Set the compiler complience to C99 or later.

or

Change the initializer to initialize all elements of the array:

static const cli_pulldown_t pulldown_values[] =
{
    {0,  NULL, 0.0},  // Added initializer for element 0
    {1,  {TB}, 1.0},
    {4,  {TBT, BT, BTB, TB},                     1.25},
    {2,  {PIC_STRUCT_DOUBLE, PIC_STRUCT_TRIPLE}, 1.0},
    {1,  {PIC_STRUCT_DOUBLE},                    2.0},
    {1,  {PIC_STRUCT_TRIPLE},                    3.0},
    {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}
};

Upvotes: 1

kec
kec

Reputation: 2149

Others have said what it is. Compiling with C compiler, not C++, should fix it, since it's not a standard part of C++.

Upvotes: 1

plinth
plinth

Reputation: 49199

That's called a designated initializer. You can read more about it here.

Upvotes: 3

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