X-Git-Url: https://git.distorted.org.uk/~mdw/sod/blobdiff_plain/a1985b3cf0ca42f573b8599ec50a0f162a26c314..8698accbb89627bf7358f6614de713be11bde3b8:/src/c-types-proto.lisp

diff --git a/src/c-types-proto.lisp b/src/c-types-proto.lisp
index 43824da..0ce2cf3 100644
--- a/src/c-types-proto.lisp
+++ b/src/c-types-proto.lisp
@@ -46,8 +46,11 @@
 
 (export 'canonify-qualifiers)
 (defun canonify-qualifiers (qualifiers)
-  "Return a canonical list of qualifiers."
-  (delete-duplicates (sort (copy-list qualifiers) #'string<)))
+  "Return a canonical list of qualifiers.
+
+   Duplicates and `nil' entries are deleted, and the remaining entries are
+   sorted."
+  (sort (delete-duplicates (delete nil (copy-list qualifiers))) #'string<))
 
 (export 'qualify-c-type)
 (defgeneric qualify-c-type (type qualifiers)