Re: encapsulating directory operations

On 30/05/2025 12:54, Richard Heathfield wrote:

On 30/05/2025 10:20, David Brown wrote:

On 29/05/2025 14:38, Richard Heathfield wrote:
>

This really is a very simple point, but perhaps a simple analogy will help to clarify it. You don't throw out your 3/4" just because you've bought a 19mm. There is room for both in the toolbox, and why write 3/4" on your new spanner? It /isn't/ a 3/4" spanner even though it's very like it, so why pretend otherwise?
>

>
Your analogy does not cover C99 vs C90.

 It does if we can construct a program that is legal C90 but not legal C99, which is easy enough, or (slightly harder but still not that hard) a program that is legal in both dialects but which gives different output under C99 than it does for C90.
 $ cat c9099.c;gcc -W -Wall -ansi -pedantic -o c90 c9099.c;gcc -o c99 c9099.c;./c90;./c99
#include <stdio.h>
 int main(void)
{
   int a = 42;
    int b = a //* comment */ 6;
   ;
   printf("Soln = %d\n", b);
    return 0;
}
Soln = 7
Soln = 42
 Obviously it's a contrived example, but then examples pointing out the consequences of language differences invariably are.
 

The analogy there is like complaining you can't use the back end of your new spanner to hammer in nails, because it now has a box/ring at the end.
About the only non-pathological circumstances where a C90 program could not be compiled as C99 and give the same result is if you happened to use the word "restrict" as an identifier.
(And yes, I know there was a minor change in the types of certain integer constants, and that it is conceivable that a particularly unusual C90 compiler gave different unspecified rounding for negative division than on a C99 compiler.)