Newbie: Array of pointers to strings questions.

[Keith Thompson]

It is elusive _because_ you would never write it that way. The OP is
possibly the first person ever to have used the sizeof operator on a
function call.

I doubt it. In fact, I can imagine applying the sizeof operator to a
function call actually being useful. It gives you the size in bytes
of the function's result without calling the function (since the
operand of sizeof isn't evaluated unless it's a VLA).

 

[CBFalconer]

... snip ...

void free_ptrs(char **s, size_t nmemb)
{
while (nmemb-- != 0) {
free(s[nmemb]);
}
}

A slight reorganization adds a world of safety, and makes it do
the right thing when nmemb is zero.

void free_ptrs(char **s, size_t nmemb)
{
while (nmemb) free(s[--nmemb]);
}

The only difference I see between the 2 versions is the value of
nmemb after the loop terminates. But since that value isn't used
and is well defined in both cases they are functionally equivalent.

I do think your version is cleaner however.

Apologies. The original does work correctly. I was thinking
(faultily) that it would do the unsigned wrap around thing and run
indefinitely for an input value of zero, while trying to access
non-existing array members.

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[Christian Kandeler]

In fact, I can imagine applying the sizeof operator to a
function call actually being useful. It gives you the size in bytes
of the function's result without calling the function (since the
operand of sizeof isn't evaluated unless it's a VLA).

While you are technically correct (I wasn't aware that the function doesn't
get called), I would find such as construct rather confusing, if not
obfuscating. IMHO, this outweighs the advantage of not having to hard code
the data type explicitly. I will therefore continue to write sizeof(int)
instead of sizeof printf("Hello World\n").


Christian