Thread: Simple include issue with code::blocks

I am starting a new project in codeblocks using the default settings. I have three .c files that I need to link together, and I am apparently doing it wrong.

main.c looks like this:

Code:

#include<time.h>
#include<windows.h>
#include<stdint.h>
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include"detection.h"
#include"io.h"
#include"butterworth.h"



int main(int argc, char **argv)
{
    //allocate and read configuration struct
    configuration *config;
    if ((config = malloc(sizeof(configuration)))==NULL)
    {
        printf("Cannot allocate config structure\n");
        abort();
    }
    read_config(config);


    return 0;
}

detection.c looks like this:

Code:

#include"detection.h"

nothing there yet, still working on getting things set up properly.


detection.h defines a struct

Code:

struct Configuration
{
    ...stuff...
};
typedef struct Configuration configuration;

io.c reads stuff into the struct

Code:

#include"io.h"
#define STRLENGTH 1024
void read_config(configuration *config)
{
     ...stuff....
}

and io.h just declares that function

Code:

void read_config(configuration *config);

When I try to build, I get "Error: unknown type name configuration"

so apparently things are not being included properly. Can anyone suggest what I am doing wrong?

if io.c or io.h doesn't include detection.h, that struct won't be visible to that source file.

welp, that should have been obvious ^_^. I blame Friday morning with no coffee.

I guess a better way to do it would be to declare all the structs that are needed in multiple .c files in a separate structs.h file and #include that in all of the .c files, along with appropriate include guards.

Fair enough. My .h files now look like this:

Code:

#ifndef DETECTOR_H_INCLUDED
#define DETECTOR_H_INCLUDED
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#include<stdint.h>
#include<inttypes.h>
#include<time.h>

struct Configuration
{
    ...things...
};
typedef struct Configuration configuration;




int signum(double num);

#endif // DETECTOR_H_INCLUDED

Code:

#ifndef IO_H_INCLUDED
#define IO_H_INCLUDED
#include"detection.h"

void read_config(configuration *config);
#endif // IO_H_INCLUDED

and main.c #includes both .h files:

Code:

#include"detection.h"
#include"io.h"

No need for guards there, correct?

Additional, unrelated question. I am using uint64_t types, and the proper way to print these is

Code:

printf("%" PRIu64 "\n",num);

That macro evaluates to "I64u" - why wouldn't I simply using

Code:

printf("%I64u\n",num);

Does that imply loss of portability since that macro might be implementation dependent?

Not quite right. Don't include all the headers you're using for the whole program, in one .h file. Each file (.c or .h) should only include the headers that it directly uses/references itself. Thus, if you don't reference anything from stdio.h in detector.h, don't include it in there. If all detector.h has is a struct/type definition and a function prototype, then it does not need to #include anything. Just include guards, the struct and . The .c files that use printf or whatever, will each #include <stdio.h>. Make sense?

But if, for example, I remove the #define<inttypes.h> from detector.h, I get the error: unknown type uint64_t (there are a few of these declared in the struct). Doesn't the .h file where the struct is declared need that header file in it? Or should I be defining the struct in the .c file?

Oh, I misunderstood. I thought you were discouraging me from including standard libraries in .h files altogether. All is clear now.

Originally Posted by anduril462

Each file (.c or .h) should only include the headers that it directly uses/references itself. Thus, if you don't reference anything from stdio.h in detector.h, don't include it in there.

At the risk of encouraging bad habits, I always include the following header at the top of any module that uses any of the standard library facilities

Code:

#include "ct/standard_headers.h"

Where "ct/" is a custom prefix to avoid name conflicts and "standard_headers.h" is a header that includes every header defined by the standard library. Obviously not all headers are needed, but if you think about it there is almost never a good reason not to include them all. When you distribute the source of this module to someone else you can either distribute your own custom header along with it or else you go replace such "shortcuts" with the actual standard headers that each module uses (a task which is best left to a major release of the project anyway).

For 3rd party libraries you can do the same thing to save time and headaches. With these libraries you also sometimes need to rely on preprocessor black magic to get them to compile cleanly with your implementation, or to make sure you get feature X, Y or Z that is supplied with that library. This way you hide such nonsense behind a clean interface that everyone can understand. E.g.

Code:

#include "ct/standard_headers.h"
#include "ct/apr_headers.h"
#include "ct/curses_headers.h"
#include "foo.h"

void foo() {
    ...
}