diff --git a/lib/atoi/a2i.h b/lib/atoi/a2i.h
index 96d468ec40..eebb43db84 100644
--- a/lib/atoi/a2i.h
+++ b/lib/atoi/a2i.h
@@ -13,6 +13,7 @@
 
 #include "atoi/strtoi/strtoi.h"
 #include "atoi/strtoi/strtou_noneg.h"
+#include "cast.h"
 #include "typetraits.h"
 
 
@@ -35,7 +36,7 @@
 		unsigned int:       strtou_noneg,                     \
 		unsigned long:      strtou_noneg,                     \
 		unsigned long long: strtou_noneg                      \
-	)(s, (char **) endp_, base, min_, max_, &status);             \
+	)(s, const_cast(char **, endp_), base, min_, max_, &status);  \
 	                                                              \
 	if (status != 0)                                              \
 		errno = status;                                       \
diff --git a/lib/cast.h b/lib/cast.h
index e8e42e1a0b..6bb5971b5b 100644
--- a/lib/cast.h
+++ b/lib/cast.h
@@ -9,7 +9,7 @@
 #include "config.h"
 
 
-#define const_cast(T, p)  _Generic(p, const T:  (T) (p))
+#define const_cast(T, p)  _Generic(p, const T: (T) (p), default: (p))
 
 
 #endif  // include guard
diff --git a/lib/string/strcmp/strcaseprefix.h b/lib/string/strcmp/strcaseprefix.h
index b001076b6b..70bbaac70b 100644
--- a/lib/string/strcmp/strcaseprefix.h
+++ b/lib/string/strcmp/strcaseprefix.h
@@ -13,22 +13,14 @@
 
 #include "attr.h"
 #include "cast.h"
+#include "typetraits.h"
 
 
-// string case-insensitive prefix
+// strcaseprefix - string case-insensitive prefix
 #define strcaseprefix(s, prefix)                                      \
-({                                                                    \
-	const char  *p_;                                              \
-	                                                              \
-	p_ = strcaseprefix_(s, prefix);                               \
-	                                                              \
-	_Generic(s,                                                   \
-		const char *:                     p_,                 \
-		const void *:                     p_,                 \
-		char *:        const_cast(char *, p_),                \
-		void *:        const_cast(char *, p_)                 \
-	);                                                            \
-})
+(                                                                     \
+	const_cast(QChar_of(s) *, strcaseprefix_(s, prefix))          \
+)
 
 
 ATTR_STRING(1) ATTR_STRING(2)
diff --git a/lib/string/strcmp/strprefix.h b/lib/string/strcmp/strprefix.h
index 3abffb5f4e..40449f3828 100644
--- a/lib/string/strcmp/strprefix.h
+++ b/lib/string/strcmp/strprefix.h
@@ -13,22 +13,14 @@
 
 #include "attr.h"
 #include "cast.h"
+#include "typetraits.h"
 
 
-// string prefix
+// strprefix - string prefix
 #define strprefix(s, prefix)                                          \
-({                                                                    \
-	const char  *p_;                                              \
-	                                                              \
-	p_ = strprefix_(s, prefix);                                   \
-	                                                              \
-	_Generic(s,                                                   \
-		const char *:                     p_,                 \
-		const void *:                     p_,                 \
-		char *:        const_cast(char *, p_),                \
-		void *:        const_cast(char *, p_)                 \
-	);                                                            \
-})
+(                                                                     \
+	const_cast(QChar_of(s) *, strprefix_(s, prefix))              \
+)
 
 
 ATTR_STRING(1)