Annoying prototypes for execv* functions in V.4 <sys/unistd.h>

[Doug Gwyn]

In article <3598 at lupine.NCD.COM> rfg at lupine.ncd.com (Ron Guilmette) writes:
>I'm fairly sure that these declarations should be changed to:
>extern int execv(const char *, const char *const *);
>extern int execve(const char *, const char *const *, const char *const *);
>extern int execvp(const char *, const char *const *);

Unfortunately there is no "right" way to do this.  Pointer-to-const has
special meaning in function parameter declarations, not quite in line
with the meaning in other forms of declaration.  In particular, type
compatibility checking will approve of passing a pointer to non-const
at the "first" level, but not at the second level of referencing.  Thus
the common usage
	char *args[] = { "prog", "arg1", NULL };
	execv( args[0], args );
would cause an "incompatible types for second argument" diagnostic,
were <unistd.h> (what is this "sys/" prefix?) to provide the additional
"const"s that you suggest.  You can legitimately consider this a
technical deficiency in the C standard if you wish; we simply couldn't
figure out an acceptable way to specify what one would really want for
this and therefore just fixed up the spec for the top level of
referencing.