Looping a statically allocated array, outside of c99 mode?

Question

This is in reference to a solution posted on: Looping a fixed size array without defining its size in C

Here's my sample code:

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

int main(int argc, char *argv[])
{
    static const char *foo[] = {
           "this is a test",
           "hello world",
           "goodbye world",
           "123", 
           NULL
    };

    for (char *it = foo[0]; it != NULL; it++) {
        printf ("str %s\n", it);
    }

    return 0;

}

Trying to compile this gives:

gcc -o vararray vararray.c
vararray.c: In function ‘main’:
vararray.c:14: warning: initialization discards qualifiers from pointer target type
vararray.c:14: error: ‘for’ loop initial declaration used outside C99 mode

Clarify: C99 mode "forbidden", and you need the work-around -- OR -- you are open to using C99 mode? — Roboprog, Dec 28 '09 at 16:16

score 7 · Accepted Answer · answered Dec 28 '09 at 14:40

Besides the initialization in the for loop, you're incrementing in the wrong place. I think this is what you mean (note that I'm not exactly a C guru):

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

int main(int argc, char *argv[])
{
    static const char *foo[] = {
           "this is a test",
           "hello world",
           "goodbye world",
           "123", 
           NULL
    };
    const char **it;
    for (it=foo; *it != NULL; it++) {
        printf ("str %s\n", *it);
    }

    return 0;

}

Yep, it++ makes sense only for **. – diciu Dec 28 '09 at 14:41 — diciu, Dec 28 '09 at 14:41

score 6 · Answer 2 · answered Dec 28 '09 at 14:36

Your loop variable it is of type char*, the contents of the array are of type const char*. If you change it to be also a const char* the warning should go away.
You declare it inside the for statement, this is not allowed in C before C99. Declare it at the beginning of main() instead.
Alternatively you can add -std=c99 or -std=gnu99 to your gcc flags to enable the C99 language features.

Prasoon Saurav · Answer 3 · 2009-12-28T14:42:17.190

1

Use -std=c99 option when compiling your code in order to use the C99 features.

Change it to const char* type ( to remove the warnings)

edited Dec 28 '09 at 14:42

answered Dec 28 '09 at 14:36

Prasoon Saurav

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score 0 · Answer 4 · answered Dec 28 '09 at 14:36

0

Before C99, declaring that character pointer in the for loop is non-standard.

answered Dec 28 '09 at 14:36

Drew Dormann

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score 0 · Answer 5 · answered Dec 28 '09 at 14:36

0

You need two things to have this compile without warnings: declare the iterator const char* it, and do it at the beginning of the function and not in the loop statement.

answered Dec 28 '09 at 14:36

Nikolai Fetissov

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Looping a statically allocated array, outside of c99 mode?

5 Answers5