Thread: Realloc Quick Question.

Originally Posted by killpoppop

But as far as i can see no word is larger than 30 characters. But i'm obvious not on your wavelength =]

Yes, I noticed that, so the problem lies elsewhere. Unlike MK27, I experienced a crash when running your code.

The first thing I would do is to avoid dynamic memory allocation:

Code:

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

void read( FILE *text )
{
    int i = 0;
    int z;
    char temp[30];

    /* Reads in the words one at a time to an array */
    while( ( z = fgetc(text) ) != EOF )
    if( i < ( sizeof( temp ) - 1 ) && ( isalpha( z ) || z == '-' || z == '\'' ) )
    {
        temp[i] = toupper( z );
        i++;
    }
    else if( i != 0 )
    {
        temp[i] = '\0';
        printf( "%s %d\n", temp, strlen( temp ) );
        i = 0;
    }
}

int main( int argc, char *argv[] )
{
	FILE *text;
	if( argc != 2 )
	{
		printf( "Incorrect Syntax" );
	}
	else
    {
		text = fopen( argv[1], "r" );
	    read( text );
    }
	return 0 ;
}

Now, if you are to return a pointer from read() so that it can be linked into a linked list, you would need to use dynamic allocation instead of merely printing out the string (and in fact no printing should be done in read(), except maybe to print an error message).

Originally Posted by killpoppop

But i'm obvious not on your wavelength =]

Maybe someone else can confirm what I just posted?
edit: sorry laserlight.

I guess that is strange. -Wall complained that strlen returns a size_t, not an int (to printf). (FC10/64)

ps. I take that an MS Crash is just, like, a pop-up window???

Originally Posted by MK27

I guess that is strange.

Not really. Undefined behaviour is probably at work here, so it can crash on one machine and not on another.

Originally Posted by laserlight

Undefined behaviour

There should be a special flashing red LED on the keyboard for this.

Thanks a lot laserlight. So if i want to use dynamic memory allocation i do it elsewhere rather than in the read function?

Also could you explain

Code:

( isalpha( z ) || z == '-' || z == '\'' )

quickly please?

Originally Posted by killpoppop

So if i want to use dynamic memory allocation i do it elsewhere rather than in the read function?

No, I think that it is correct to do it in the read function, and then later you let the linked list do the memory management. One approach is to make read() read in just one word. Another approach is to pass a pointer to the head of the linked list to read(), then read will append to the linked list while it reads in the words. The second approach is more like what you are doing now.

Originally Posted by killpoppop

Also could you explain

Do you understand what this code does?

Code:

if( ( ( 65 <= z ) && ( z <= 90 ) ) || ( ( 97 <= z ) && ( z <= 122 ) ) || ( z == 45 ) || ( z == 39 ) )

My version does the same but is more readable since it can easily be read as: "if z is an alphabetic character, a dash or a single quote". With your version, a reader who does not have the ASCII table at his or her fingertips must look it up. (It also is less portable since it assumes ASCII, but that is more of a theoretical concern these days.)