On Fri, Apr 26, 2019 at 10:28:12AM -0400, Johannes Schindelin wrote:

quoted

quoted

+static gzFile gzip;
[...]
+       if (gzip) {

Is it OK for us to ask about the truthiness of this opaque type? That
works if it's really a pointer behind the scenes, but it seems like it
would be equally OK for zlib to declare it as a struct.

It looks OK in my version of zlib, and that library tends to be fairly
conservative so I wouldn't be surprised if it was that way back to the
beginning and remains that way for eternity. But it feels like a bad
pattern.

It is even part of the public API that `gzFile` is `typedef`'d to a
pointer. So I think in the interest of simplicity, I'll leave it at that
(but I'll mention this in the commit message).

I think that's probably OK. My biggest concern is that we'd notice if
our assumption changes, but I think modern compilers would generally
complain about checking a tautological truth value.

-Peff