macro function

[bradleyd]

Hello everyone,
I am stuck and confused about macros. I need to define a macro that returns the HOME dir of user. This is what I have so far:

#define GLADE_FILE { \
    char *homeDir = getenv("HOME"); \
    char *tempi = "/hello.glade"; \
    strcat(homeDir, tempi); \ 
    printf("%s", homeDir); \
}

as you can see it does not work. If I try to put it into a regular function and try to pass homeDir with return(homeDir)
I get

home-dir.c:19: warning: return makes integer from pointer without a cast

Any help would be great,
Thanks in advance.
Brad

[MacGyver]

You can't just strcat them together like that. I doubt getenv() will return enough of a buffer to guarentee that it will be safe.

In reality, you should make this into a function imo.

[Brian]

Hello everyone,
I am stuck and confused about macros. I need to define a macro that returns the HOME dir of user. This is what I have so far:

#define GLADE_FILE { \
    char *homeDir = getenv("HOME"); \
    char *tempi = "/hello.glade"; \
    strcat(homeDir, tempi); \ 
    printf("%s", homeDir); \
}

as you can see it does not work. If I try to put it into a regular function and try to pass homeDir with return(homeDir)
I get
Any help would be great,
Thanks in advance.
Brad

#define PATHLEN 256 

 char mypath[PATHLEN] = { '\0' };
 char *homeDir = getenv("HOME");
 strncpy(mypath, homeDir, PATHLEN);
 strncat(mypath, "/hello.glade", PATHLEN - strlen(mypath));
 printf("%s", mypath);

[bradleyd]

I tried to put it into a function then call the function but I get that error. Here is the function:

char hd(void)
{
	char *homeDir = getenv("HOME");
    char *temp = "/hello.glade";
    strcat(homeDir, temp);
    return(homeDir);
}

if I substitute return(homeDir) with printf("%s",homeDir);
it works fine.

[MacGyver]

If you just want to print it without any error checking, then you could do something like this:

#define printglade() printf("%s/hello.glade",getenv("HOME"))

Since getenv() can return NULL, this is probably not a good idea.

If you need to return a string:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *getGlade(void);

int main(void)
{
	char *szGlade = getGlade();
	
	if(szGlade)
	{
		printf("Glade directory: <%s>\n",szGlade);
		free(szGlade);
	}
	else perror("Unable to retrieve Glade directory.");
	
	return 0;
}

char *getGlade(void)
{
	char *homeDir,*temp = "/hello.glade",*szReturn = NULL;
	
	homeDir = getenv("HOME");
	if(homeDir)
	{
		szReturn = malloc(strlen(homeDir) + strlen(temp) + 1);
		if(szReturn)
		{
			strcpy(szReturn,homeDir);
			strcat(szReturn,temp);
		}
	}
	return szReturn;
}

[zacs7]

I tried to put it into a function then call the function but I get that error. Here is the function:

char hd(void)
{
	char *homeDir = getenv("HOME");
    char *temp = "/hello.glade";
    strcat(homeDir, temp);
    return(homeDir);
}

if I substitute return(homeDir) with printf("%s",homeDir);
it works fine.

Your supposed to return a char pointer (char *) not a char, see MacGyver's post.

[bradleyd]

Thanks that worked, I kinda foggy on char *GetHome vs. char GetHome. If you want to return any string from a function do you always have use a pointer in declaring the function?
when you want to return a int you just int SomeNumber(void).
Just having trouble grasping that.
Thanks,
Brad

[MacGyver]

A string is a set of chars that are sequential in memory, ending with a final '\0' char. One way of representing such a data type can be done using a char array. A char array, down deep under the hood, is represented simply by a pointer to the first element of the array. This means to return a string, you have to return a char *. If you return a char, you only return one character.

[bradleyd]

ok that makes sense, thanks MacGyver.
Pointers seem to be my weak point in C.