Struct defined in the file.auxiliary c (with Function Definition and structs) is not recognized in main

Question

Struct defined in the file.auxiliary c (with Function Definition and structs) is not recognized in main

I'm doing a project in C, and I have 3 files:

1 .c containing the definitions of functions and structs.

1 .h containing the prototypes of these functions and structs

Ae1 .C containing the main.

No .c with the definitions, I defined the struct:

typedef struct vector {

    int numDePosicoes;
    double vetor[5000];

}ESTRUCT;

And in the main method, I try to create an instance of this struct as follows:

int main(int argc,char* argv[]) {

    ESTRUCT vetor;

    //criando separadamente um ponteiro para a struct
    ESTRUCT *ponteiroPraVetor = &vetor;

But gcc accuses the error: "error :unknown type name' ESTRUCT’ "

Both na struct creation, when in the creation of the pointer to it.

Note: I'm using a Makefile to mount the program, follow it below:

CFLAGS=-Wall

Roteiro5exe:    mainr5.o    Roteiro5.o

mainr5.o:   mainr5.c    Roteiro5.h

Roteiro5.o: Roteiro5.c  Roteiro5.h

clean:
    rm *.o

Note: when I put all the code in the same file, and simply compile it, it works. Maybe the problem is in the makefile. Can anyone see it?

1

c struct gcc makefile

Author: Lucas Pletsch, 2016-07-15

Source

1 answers

score 0 · Answer 1

It seems to me that you are confusing statement with definition. Whenever you want to use something, you need to declare it. Declaring means introducing something to the system. For example:

extern int a;
typedef struct { int a;} X;
void print();

Define means to give a body to the statements. You can imagine how to create a space in memory, where the statements will live. For example:

int a = 1;
X k;
void print() {}

Definitions are usually placed in a file .C, while statements are usually placed in file .h. This is necessary because whenever you are going to use a definition, you have to see the statement.

So in your case the statement of ESTRUCT is in the wrong place. This is not a definition, it is a statement and it should be seen in all files where you want to use it. Therefore, you must declare it in a file .H and include this file where is the function main which by the way, is where you make a definition when writing:

ESTRUCT vetor;