Re: require() parse error in 5.3.4/5.4.0-work2?
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- Subject: Re: require() parse error in 5.3.4/5.4.0-work2?
- From: Sean Conner <sean@...>
- Date: 2018年6月27日 13:02:03 -0400
It was thus said that the Great Kenneth Lorber once stated:
> > On Jun 23, 2018, at 8:57 AM, Andrew Gierth <andrew@tao11.riddles.org.uk> wrote:
> >
> > Pretty much every function accepts and silently ignores extra arguments,
> > unless the function itself bothers to check for them and throw an
> > explicit error.
>
> Thanks, and after a little source diving you are correct, but that's not
> quite the reply I was looking for.
>
> Is there some reason this is a language feature? Some use-case I don't
> see? (If so, why is there the occasional check for extra arguments?)
It's not just Lua. Here's an example in C:
----[ x.c ]------
#include <stdio.h>
extern int foo();
int main(void)
{
int x = foo(1,2,3,4,5);
printf("%d\n",x);
return 0;
}
----[ y.c ]-----
extern foo(int,int); // to shut up clang
int foo(int a,int b)
{
return a + b;
}
[spc]dynamic-147:/tmp>gcc -ansi -pedantic -Wall -Wextra x.c y.c
[spc]dynamic-147:/tmp>clang -ansi -pedantic -Wall -Wextra -Weverything x.c y.c
[spc]dynamic-147:/tmp>./a.out
3
No warnings. No errors. I'm passing way more parameters to foo() than it
is expecting. And it works. Granted, I'm using an outdated style of
function prototype which in C means "this function takes an unspecified
number of arguments and returns an integer" (at least in x.c; y.c has the
proper prototype, but that's to shut up clang about a missing function
prototype that GCC doesn't report).
> Is it documented somewhere I missed?
>
> Is there any reason not to add checks for extra arguments? If it's
> performance, it could be available as a compile time option.
It's performance, and it doesn't hurt. I'm also not sure how easy it
would be to catch at compile time.
-spc