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Message-Id: <A85FE2D1-89CB-4892-8696-AD5477582B57@palsenberg.com>
Date: Tue, 15 Jan 2013 23:28:14 +0100
From: Igmar Palsenberg <igmar@...senberg.com>
To: musl@...ts.openwall.com
Subject: Re: malloc(0) behaviour
>>
>> That's there to access if size is 0 ? Sure, you can access :
>>
>> struct foo {
>> };
>
> This is a constraint violation. C does not allow empty structs, and
> even if it did, they would not have size 0, since no type or object
> ever has size 0 in C.
GCC thinks otherwise :
#include <stdlib.h>
#include <stdio.h>
struct test {
};
int main(int argc, char **argv)
{
char *x = NULL;
printf("sizeof test : %d\n", sizeof(struct test));
return 0;
}
[igmar@...el ~]$ ./x
sizeof test : 0
It gives me a warning, but doesn't error out. Olders version might behave differently, I don't have those installed. The LLVM compiler does the same.
No idea what the standard says, but your remarks sounds correct to me.
>>
>> which is size 0. I do wonder what that gives me in practice. That is, not counting the fact that :
>>
>> if (size == 0)
>> size = 1;
>>
>> was a common practice in malloc() implementations a while ago.
>
> Of course, this is the canonical, simplest way to make malloc(0)
> return a unique pointer.
Enough for this thread. I did got the answer I wanted, and the result I want is easy to realise. Not mu intention to irritate people.
Igmar
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