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Another question regarding memory

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Join Date: Jan 2005

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kloony

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Re: Another question regarding memory

#11

Mar 10th, 2005

Thanks, Narue and Stack Overflow (esp. for your memory allocation techniques).

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Re: Another question regarding memory

#12

Mar 10th, 2005

Hello,

You're welcome. If you have any further questions regarding the information I provided, don't hesitate to ask.

- Stack Overflow

Following the rules will ensure you get a prompt answer to your question. If posting code, please include BB [code][/code] tags. Your question may have been asked before, try the search facility.

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kloony

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Re: Another question regarding memory

#13

Mar 13th, 2005

Dear Stack Overflow,

I have a funny observation which I am not sure if it makes any sense. With regards to your code

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
/* free rows made by MATRIXint() */
/* where V represents the rows */
for (i = V-1; i >= 0; i--) {
	if (G->adj[i] != NULL) {
		free(G->adj[i]);
		G->adj[i] = NULL;
	}
}
 
/* free 2-dimensional pointer */
if (G->adj != NULL) {
	free(G->adj)
	G->adj = NULL;
}
 
/* free Graph */
if (G != NULL) {
	free(G);
	G = NULL;
}
/* free rows made by MATRIXint() */
/* where V represents the rows */
for (i = V-1; i >= 0; i--) {
	if (G->adj[i] != NULL) {
		free(G->adj[i]);
		G->adj[i] = NULL;
	}
}

/* free 2-dimensional pointer */
if (G->adj != NULL) {
	free(G->adj)
	G->adj = NULL;
}

/* free Graph */
if (G != NULL) {
	free(G);
	G = NULL;
}

it appears that when I use it to free up memory used for my graph G in the main program, it works, but when I write it as a function and include it as a header file as follows

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
void freegraph(G)
{ int i;
/* free rows made by MATRIXint() */
/* where V represents the rows */
for (i = (G->V)-1; i >= 0; i--) {
	if (G->adj[i] != NULL) {
		free(G->adj[i]);
		G->adj[i] = NULL;
	}
}
 
/* free 2-dimensional pointer */
if (G->adj != NULL) {
	free(G->adj)
	G->adj = NULL;
}
 
/* free Graph */
if (G != NULL) {
	free(G);
	G = NULL;
}
void freegraph(G)
{ int i;
/* free rows made by MATRIXint() */
/* where V represents the rows */
for (i = (G->V)-1; i >= 0; i--) {
	if (G->adj[i] != NULL) {
		free(G->adj[i]);
		G->adj[i] = NULL;
	}
}

/* free 2-dimensional pointer */
if (G->adj != NULL) {
	free(G->adj)
	G->adj = NULL;
}

/* free Graph */
if (G != NULL) {
	free(G);
	G = NULL;
}

it doesn't work. I passed my graph G to this function and then had the following code in my main function

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
if(G==NULL)printf("success"); else printf("fail");
if(G==NULL)printf("success"); else printf("fail");

I got fail instead of the expected success. Why is this so?