On 01/25/2017 03:08 PM, Rich Felker wrote:
FWIW this technique is non-conforming, at least for any standard
functions it's used on, since it breaks pointer equality. A conforming
program can evaluate p1==p2, where p1=dlsym is assigned in one dso and
p2=dlsym is assigned in another, and must see equality on a conforming
implementation. As such I think this hack needs to be removed from
other functions like stat.
Is there a specific requirement in POSIX to that effect, or is it an
accident as the result of how POSIX and ISO C interact?
As far as I can tell, ISO C specifies function pointer equality by
saying that pointers compare equal iff they refer to the “same […]
function”, but the standard does not seem to define what makes two
functions the same.
(But even if it is fully conforming or acceptable for other reasons, I
dislike the __dso_handle technique because it is too complex.)