[PATCH v3 16/19] grep.c: refactor free_grep_patterns()

[Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>]

Refactor the free_grep_patterns() function to split out the freeing of
the "struct grep_pat" it contains, right now we're only freeing the
"pattern_list", but we should be freeing another member of the same
type, which we'll do in the subsequent commit.

Let's also replace the "return" if we don't have an
"opt->pattern_expression" with a conditional call of
free_pattern_expr().

Before db84376f981 (grep.c: remove "extended" in favor of
"pattern_expression", fix segfault, 2022-10-11) the pattern here was:

	if (!x)
		return;
	free(y);

But after the cleanup in db84376f981 (which was a narrow segfault fix,
and thus avoided refactoring this) we ended up with:

	if (!x)
		return;
	free(x);

Let's instead do:

	if (x)
		free(x);

This doesn't matter for the subsequent change, but as we're
refactoring this function let's make it easier to reason about, and to
extend in the future, i.e. if we start to free free() members that
come after "pattern_expression" in the "struct grep_opt".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
 grep.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/grep.c b/grep.c
index 06eed694936..a4450df4559 100644
--- a/grep.c
+++ b/grep.c
@@ -769,11 +769,11 @@ static void free_pattern_expr(struct grep_expr *x)
 	free(x);
 }
 
-void free_grep_patterns(struct grep_opt *opt)
+static void free_grep_pat(struct grep_pat *pattern)
 {
 	struct grep_pat *p, *n;
 
-	for (p = opt->pattern_list; p; p = n) {
+	for (p = pattern; p; p = n) {
 		n = p->next;
 		switch (p->token) {
 		case GREP_PATTERN: /* atom */
@@ -790,10 +790,14 @@ void free_grep_patterns(struct grep_opt *opt)
 		}
 		free(p);
 	}
+}
 
-	if (!opt->pattern_expression)
-		return;
-	free_pattern_expr(opt->pattern_expression);
+void free_grep_patterns(struct grep_opt *opt)
+{
+	free_grep_pat(opt->pattern_list);
+
+	if (opt->pattern_expression)
+		free_pattern_expr(opt->pattern_expression);
 }
 
 static const char *end_of_line(const char *cp, unsigned long *left)
-- 
2.39.0.1195.gabc92c078c4