wildmatch: explicitly mark intentional use of the comma operator

The comma operator is a somewhat obscure C feature that is often used by
mistake and can even cause unintentional code flow. That is why the
`-Wcomma` option of clang was introduced: To identify unintentional uses
of the comma operator.

To mark such a usage as intentional, the value needs to be cast to
`void`, which we do here.

In this instance, the usage is intentional because it allows storing the
value of the current character as `prev_ch` before making the next
character the current one, all of which happens in the loop condition
that lets the loop stop at a closing bracket.

The alternative to using the comma operator would be to move those
assignments from the condition into the loop body; In this particular
case that would require the assignments to either be duplicated or to
introduce and use a `goto` target before the assignments, though,
because the loop body contains a `continue` for the case where a
character class is found that starts with `[:` but does not end in `:]`
(and the assignments should occur even when that code path is taken).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

wildmatch.c

@@ -268,7 +268,7 @@ static int dowild(const uchar *p, const uchar *text, unsigned int flags)
 					p_ch = 0; /* This makes "prev_ch" get set to 0. */
 				} else if (t_ch == p_ch)
 					matched = 1;
-			} while (prev_ch = p_ch, (p_ch = *++p) != ']');
+			} while ((void)(prev_ch = p_ch), (p_ch = *++p) != ']');
 			if (matched == negated ||
 			    ((flags & WM_PATHNAME) && t_ch == '/'))
 				return WM_NOMATCH;