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I am working on C Structures. I want to #define the struct values as follows.
// #define get_x() { .y = { .z = 1, .c = "test" } }; // this is working
// But I want to replace the above line with
#define get_y() { .z = 1, .c = "test" };
#define get_x() { .y = get_y() }; // this gives error
struct :
typedef struct {
int z;
char c[10];
} y_t;
typedef struct {
y_t y;
} x_t;
int main()
{
x_t x = get_x();
printf("c: %s", x.y.c);
return 0;
}
Will you please help me know, How can I do that?
Remove the ;, there is no ; in initialization. Typically, macros are in upper case.
#define GET_Y() { .z = 1, .c = "test" }
#define GET_X() { .y = GET_Y() }
typedef enum
{
ONE = 1,
TWO = 2,
THREE = 3
}Count_t;
typedef enum
{
RED = 0,
BLUE = 1,
GREEN = 2
}Color_t;
typedef struct
{
Count_t Count_en;
Color_t Color_en;
}Grp_t;
Grp_t const Grp_ena[]=
{
{ ONE, RED },
{ TWO, BLUE },
{ THREE, GREEN}
};
typedef struct
{
unsigned int num;
Grp_t * Grp_stp;
}Try_t;
Try_t const Try_sta[] =
{
{ 7, &Grp_ena[0] },
{ 8, &Grp_ena[1] },
{ 9, &Grp_ena[2] },
};
int main()
{
Try_t **p = Try_sta;
}
Using double pointer **p , I want to access the elements of LUT Try_sta. With single dimensional pointer I am able to access the struct array elements. But with 2d pointer I failed to access. Is there any proper way to do it?
In chasing down a very opaque bug, I have been trying to compile with no warnings or errors. This part of my code worked fine, but gcc complains about the braces--it says there are braces missing and extra braces. I usually initialise a bit more sloppily but here I'm being as pedantic as possible with braces for each logical level of inclusion. The only struct I really care about initialising is the last one, the Ccfg. I thought I'd build up to it gradually as it contains nested other structs, but apparently even the ones preceding it are mis-initialized according to gcc.
Here's the code:
#define max_nodes 24
struct Cseg
{
int begin;
int arc;
int end;
};
struct Node
{
struct Cseg exit[4];
};
struct Core
{
int num_circles;
int num_nodes;
struct Node node[max_nodes];
};
struct Ccfg
{
struct Core core;
int dummy1;
int dummy2;
};
int main(void)
{
struct Cseg A = {0,1,2};
struct Node B =
{
{0,1,2}, {1,3,0}, {2,-1,3}, {0,-2,1}
};
struct Node C =
{
{0,1,2}, {1,3,0}
};
struct Core D =
{4, 4,
{
{ {0,1,2}, {1,3,0}, {2,-1,3}, {0,-2,1} },
{ {1,3,0}, {2,1,0}, {3,-2,1}, {2,-1,0} },
{ {3,1,2}, {0,1,2}, {1,-3,0}, {2,-3,1} }
}
};
struct Ccfg E =
{
{2, 2,
{
{ {0,1,1}, {0,2,1} },
{ {1,2,0}, {1,1,0} }
}
}
};
return 0;
}
Some of the initialisations are incomplete; that is deliberate. My real ccfg struct has many more fields but I've simplified it for this post. If someone could let me know what I'm doing wrong I'd appreciate it a lot. Thanks!
EDIT: in my working code, the initialiser for struct Ccfg E omits the innermost braces, and works fine (but gcc still warns me about it). I added them into this test because they seemed logically appropriate, but they actually generate an error--which I don't understand.
You are missing braces in some places. Specifically, if you have an array of structs, the entire array needs to be brace-wrapped; you were just wrapping each struct entry. I just added braces as needed and it works fine now. http://ideone.com/fork/HqxB9R
#define max_nodes 24
struct Cseg
{
int begin;
int arc;
int end;
};
struct Node
{
struct Cseg ex[4];
};
struct Core
{
int num_circles;
int num_nodes;
struct Node node[max_nodes];
};
struct Ccfg
{
struct Core core;
int dummy1;
int dummy2;
};
int main(void)
{
struct Cseg A = {0,1,2};
struct Node B =
{
{ {0,1,2}, {1,3,0}, {2,-1,3}, {0,-2,1} }
};
struct Node C =
{
{ {0,1,2}, {1,3,0} }
};
struct Core D =
{4, 4,
{
{ { {0,1,2}, {1,3,0}, {2,-1,3}, {0,-2,1} } },
{ { {1,3,0}, {2,1,0}, {3,-2,1}, {2,-1,0} } },
{ { {3,1,2}, {0,1,2}, {1,-3,0}, {2,-3,1} } }
}
};
struct Ccfg E =
{
{2, 2,
{
{ { {0,1,1}, {0,2,1} } },
{ { {1,2,0}, {1,1,0} } }
}
}
};
return 0;
}
I'm trying to get a "column" elements count from my own structure using sizeof(_test.header.columns)/sizeof(struct _column). Unfortunately I'm always getting it as 0, because the sizeof(_test.header.columns) is always 4. Here is the code:
struct _column{
char title[40];
int length;
};
struct test_struct{
struct{
struct _column* columns;
}header;
struct{
struct _column* columns;
}details;
struct{
struct _column* columns;
}end;
};
struct test_struct _test = {
.header = {
.columns = {
{
"a",
1,
},
{
"ab",
2,
},
},
},
.details = {
.columns = {
{
"b",
2,
},
{
"bc",
3,
},
},
},
.end = {
.columns = {
{
"c",
3,
},
{
"cd",
4,
},
},
},
};
void testme(){
char buff[20];
itoa(sizeof(_test.header.columns)/sizeof(struct _column),buff,sizeof(buff));
MessageBoxA(NULL,buff,NULL,NULL);
}
please help me to resolve the problem, thanks. Any help would be appreciated.
You might try to do an approach like the following in which you do the same kind of initialization however you include as part of it the column count itself.
struct _column{
char title[40];
int length;
};
struct test_struct{
struct{
struct _column* columns;
int nColumns;
}header;
struct{
struct _column* columns;
int nColumns;
}details;
struct{
struct _column* columns;
int nColumns;
}end;
};
struct _column headerColumns [] = {
{
"a",
1
},
{
"ab",
2
}
};
struct _column detailColumns[] = {
{
"b",
2
},
{
"bc",
3
},
};
struct _column endColumns [] = {
{
"c",
3
},
{
"cd",
4
}
};
struct test_struct _test = {
{ headerColumns, sizeof(headerColumns)/sizeof(headerColumns[0])},
{ detailColumns, sizeof(detailColumns)/sizeof(detailColumns[0])},
{ endColumns, sizeof(endColumns)/sizeof(endColumns[0])}
};
The reason it fails is that you're checking the sizeof on a pointer, which returns the size of the pointer, NOT of the actual Array the memory address points to.
If you know the maximum length of the array, you can declare it as such:
_column[ integerSize ]
But then if you knew the size, you wouldn't be querying it using sizeof, I'd think ;-) You could extend the struct by adding another property of an int type that describes the size of the columns array ?
The following code gives me this warning:
tag_info.h:17: warning: missing braces around initializer
tag_info.h:17: warning: (near initialization for âtag_list_data[0].subtagsâ)
I have tried alot of things but nothing seems to be working. Can anyone please suggest something
typedef struct Attr{
char attr_name[64];
value_type_t value;
int mandatory;
}Attr_t;
typedef struct Tags {
unsigned int tag_id;
Attr_t *attr_list;
char *tag_name;
int tag_type;
int subtags[html_subtag_num];
}Tags_t;
Tags_t tag_list_data[150] = {
#include "tag_info.h"
{0,0,0,0,0}
};
where the "tag_info.h" contains :
#if defined(TAG_DEFINE)
#undef TAG_DEFINE
#else
#define TAG_DEFINE(a,b,c,...) {.tag_id=a, .tag_name=#b, .tag_type=c, ##__VA_ARGS__}
#endif
TAG_DEFINE(0,TAG_NONE,0,0),
TAG_DEFINE(1,!--,0,0),
TAG_DEFINE(2,!doctype,0,0),
TAG_DEFINE(3,a, 1, 1, 117, 59,11,118,92,100),
You are initializing subtags as if it were multiple members of the Tags struct:
typedef struct Tags {
...
int subtags_0;
int subtags_1;
int subtags_2;
} Tags_t;
Tags_t t = { ..., 0, 1, 2 };
But it is an array. Thus you should initialize it as a single entity.
typedef struct Tags {
...
int subtags[html_subtag_num];
} Tags_t;
Tags_t t = { .tag_id = 0, ..., { 0, 1, 2 } };
// or
Tags_t t = { .tag_id = 0, ..., .subtags = { 0, 1, 2 } };
Also, you don't need to use concatenation (##)
#define TAG_DEFINE(a,b,c,...) { ..., ## __VA_ARGS__}
In the end, it should look like
#define TAG_DEFINE(a,b,c,...) { ..., .subtags = { __VA_ARGS__ } }
...
Tags_t tag_list_data[150] = {
...
{ 0,0,0,0,{0}}
}
instead of
#define TAG_DEFINE(a,b,c,...) { ..., ##__VA_ARGS__}
...
Tags_t tag_list_data[150] = {
...
{ 0,0,0,0,0 }
}