Sort an empty list without handing qsort a null

Every list sorted here is null until its first entry, and C leaves a
null base undefined even with nothing to sort. glibc declares it
nonnull, and a UBSan build aborted the stats page of a repository with
no commits in the window.

1 file changed, 12 insertions, 0 deletions

diff --git a/source/shared.h b/source/shared.hindex e22eb57..2bf305d 100644--- a/source/shared.h+++ b/source/shared.h@@ -140,4 +140,16 @@ extern int cgit_valid_rev(const char *rev);  */ extern int cgit_notes_ref_usable(const char *notes_ref); +/*+ * qsort for a list that may be empty. C leaves a null base undefined even+ * with nothing to sort, and glibc declares it nonnull, while the lists here+ * stay null until their first entry.+ */+static inline void cgit_qsort(void *base, size_t n, size_t size,+	int (*cmp)(const void *, const void *))+{+	if (n)+		qsort(base, n, size, cmp);+}+ #endif // CGIT_SHARED_H
diff --git a/source/shared.h b/source/shared.h
index e22eb57..2bf305d 100644
--- a/source/shared.h
+++ b/source/shared.h
@@ -140,4 +140,16 @@ extern int cgit_valid_rev(const char *rev);
  */
 extern int cgit_notes_ref_usable(const char *notes_ref);
 
+/*
+ * qsort for a list that may be empty. C leaves a null base undefined even
+ * with nothing to sort, and glibc declares it nonnull, while the lists here
+ * stay null until their first entry.
+ */
+static inline void cgit_qsort(void *base, size_t n, size_t size,
+	int (*cmp)(const void *, const void *))
+{
+	if (n)
+		qsort(base, n, size, cmp);
+}
+
 #endif // CGIT_SHARED_H