On Tue, Feb 20, 2018 at 12:34 AM, Steven D'Aprano
<steve+comp.lang.pyt...@pearwood.info> wrote:
> On Mon, 19 Feb 2018 20:14:32 +1100, Chris Angelico wrote:
>
>> As an integer, 3.141590 is 1078530000 $
>>
>> Looks to me like C is perfectly happy to interpret a float as an int.
>
> Yes, but that's not an *automatic* coercion. To count as weakly typed,
> the compiler has to do it automatically, without an explicit cast or
> conversion.
Fair enough. If you ignore warnings, then C does have that kind of weak typing:
$ cat demo.c
#include <stdio.h>
int main() {
float f = 3.14159;
int *i = &f;
printf("As an integer, %f is %d\n", f, *i);
return 0;
}
$ gcc demo.c
demo.c: In function ‘main’:
demo.c:5:14: warning: initialization from incompatible pointer type
[-Wincompatible-pointer-types]
int *i = &f;
^
$
GCC was quite happy to compile that code, even though the type of "&f"
is "pointer to float", and it's being assigned to a variable of type
"pointer to int". But C is a language saddled with so much history and
backward compatibility constraints that there are some things you just
CAN'T make into errors; so in terms of "how safe is C?", I'd have to
say that warnings (especially those that are enabled by default - I
didn't need to say "-Wall" for this test), count as "disallowing",
especially if all the major compilers emit warnings on the same code.
But I do see the argument that "it compiles, so the language clearly
permits it".
ChrisA
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