using character arrays and realloc

It was my understanding that the name of an array is a pointer to it's first element. So why does this:

Code:

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char string[]="some words";
string=realloc(string, 20);

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cause error: incompatible types in assignment, meaning I have to do this instead:

Code:

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char *string;
string=malloc(11);
strcpy(string, "some words");
string=realloc(string, 20);

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Can I ask why? And is there a way out? I tried using a seperate pointer (char *ptr; ptr=string) but could not get that to work either...

A local array, like all other local variables is created on the stack. Since you didn't allocate it with malloc(), you cannot change its size with realloc() or delete it with free().
Stack variables are placed right next to each other and when the function returns, all the stack variables disappear since the stack pointer just moves back to where it was before the function was called.

Quote:

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It was my understanding that the name of an array is a pointer to it's first element.

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The name of an array is not a pointer to the first element of the array. Rather, an array is converted to a pointer to its first element when it is passed as an argument (or used in various other contexts).

Quote:

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cause error: incompatible types in assignment

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You are trying to assign a pointer into something that is an array[11]. The compiler should not allow you to do that.

And as pointed out, you can not realloc an object that wasn't created by malloc [or realloc or calloc] in the first place.

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Mats

hmmm...thanks (cpjust in particular), that clarifies a few things for me further.

Quote:

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Originally Posted by matsp

You are trying to assign a pointer into something that is an array[11]. The compiler should not allow you to do that.

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Well, it's typical C. It does work in C. Go figure.

Quote:

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Originally Posted by Elysia

Well, it's typical C. It does work in C. Go figure.

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Neither does it in C++.

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Mats

Uhh yes? You mentioned it shouldn't work and I agree. It certainly doesn't in C++, but it does work in C (as in, it compiles without errors).

Quote:

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Originally Posted by Elysia

Uhh yes? You mentioned it shouldn't work and I agree. It certainly doesn't in C++, but it does work in C (as in, it compiles without errors).

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Which part of "error: incompatible types in assignment" are you having trouble with? (Yes, that's the C error.)

Everything apparently...