gcc / 문자열 선언

weston 소스를 보는데 희한한(?) 문자열 선언이 보여서 확인

static const char * const connector_type_names[] = { [DRM_MODE_CONNECTOR_Unknown]     = "Unknown", [DRM_MODE_CONNECTOR_VGA]         = "VGA", [DRM_MODE_CONNECTOR_DVII]        = "DVI-I", [DRM_MODE_CONNECTOR_DVID]        = "DVI-D", [DRM_MODE_CONNECTOR_DVIA]        = "DVI-A", [DRM_MODE_CONNECTOR_Composite]   = "Composite", [DRM_MODE_CONNECTOR_SVIDEO]      = "SVIDEO", [DRM_MODE_CONNECTOR_LVDS]        = "LVDS", [DRM_MODE_CONNECTOR_Component]   = "Component", [DRM_MODE_CONNECTOR_9PinDIN]     = "DIN", [DRM_MODE_CONNECTOR_DisplayPort] = "DP", [DRM_MODE_CONNECTOR_HDMIA]       = "HDMI-A", [DRM_MODE_CONNECTOR_HDMIB]       = "HDMI-B", [DRM_MODE_CONNECTOR_TV]          = "TV", [DRM_MODE_CONNECTOR_eDP]         = "eDP", [DRM_MODE_CONNECTOR_VIRTUAL]     = "Virtual", [DRM_MODE_CONNECTOR_DSI]         = "DSI", [DRM_MODE_CONNECTOR_DPI]         = "DPI", };

 

느낌은 알겠는데.. 도대체 어디서 정의된 문법이냐...

$ cat str.c #include <stdio.h> static const char * const connector_type_names[] = {         [0]     = "Unknown",         [1]         = "VGA",         [2]        = "DVI-I",         [3]        = "DVI-D",         [4]        = "DVI-A",         [5]   = "Composite",         [6]      = "SVIDEO",         [7]        = "LVDS",         [8]   = "Component",         [9]     = "DIN",         [10] = "DP",         [11]       = "HDMI-A",         [12]       = "HDMI-B",         [13]          = "TV",         [14]         = "eDP",         [15]     = "Virtual",         [16]         = "DSI",         [17]         = "DPI", }; void main() {         for(int i = 0; i < 10; i++)                 printf("%s\n",connector_type_names[i]); } $ gcc str.c $ ./a.out Unknown VGA DVI-I DVI-D DVI-A Composite SVIDEO LVDS Component DIN

 

 

$ cat str.c #include <stdio.h> static const char * const connector_type_names[] = {         [2]     = "Unknown",         [1]         = "VGA",         [0]        = "DVI-I",         [3]        = "DVI-D",         [4]        = "DVI-A",         [5]   = "Composite",         [6]      = "SVIDEO",         [7]        = "LVDS",         [8]   = "Component",         [9]     = "DIN",         [10] = "DP",         [11]       = "HDMI-A",         [12]       = "HDMI-B",         [13]          = "TV",         [14]         = "eDP",         [15]     = "Virtual",         [16]         = "DSI",         [17]         = "DPI", }; void main() {         for(int i = 0; i < 10; i++)                 printf("%s\n",connector_type_names[i]); } $ gcc str.c $ ./a.out DVI-I VGA Unknown DVI-D DVI-A Composite SVIDEO LVDS Component DIN

 

 

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ISO C99, GNU C90 에서 지원하는 듯.

In ISO C99 you can give the elements in any order, specifying the array indices or structure field names they apply to, and GNU C allows this as an extension in C90 mode as well. This extension is not implemented in GNU C++. To specify an array index, write ‘[index] =’ before the element value. For example, int a[6] = { [4] = 29, [2] = 15 };

[링크 : https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html]

 

$ gcc -std=c89 str.c str.c: In function ‘main’: str.c:26:2: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode   for(int i = 0; i < 10; i++)   ^~~ str.c:26:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code $ gcc -std=c90 str.c str.c: In function ‘main’: str.c:26:2: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode   for(int i = 0; i < 10; i++)   ^~~ str.c:26:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code $ gcc -std=c99 str.c