diff --git a/include/stdlib.h b/include/stdlib.h
index 391d0446..592a387b 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -36,6 +36,7 @@ typedef int (*comparison_fn_t) (void const *, void const *);
 #include <sys/types.h>
 #include <alloca.h>
 
+void abort (void);
 double atof (char const *s);
 int atoi (char const *s);
 int atexit (void (*function) (void));
diff --git a/lib/posix/execl.c b/lib/posix/execl.c
index bae7a066..ae651510 100644
--- a/lib/posix/execl.c
+++ b/lib/posix/execl.c
@@ -38,7 +38,7 @@ execl (char const *file_name, char const *arg, ...)
   va_start (ap, arg);
 
   argv[i++] = (char *)file_name;
-  arg = va_arg (ap, char const *);
+  arg = (char *) va_arg (ap, char const *);
   while (arg)
     {
       argv[i++] = arg;
diff --git a/lib/stdio/vfprintf.c b/lib/stdio/vfprintf.c
index 00abe7a6..119e41ae 100644
--- a/lib/stdio/vfprintf.c
+++ b/lib/stdio/vfprintf.c
@@ -33,7 +33,7 @@ vfprintf (FILE * f, char const *format, va_list ap)
     if (*p != '%')
       {
         count++;
-        fputc (*p++, fd);
+        fputc (*p++, f);
       }
     else
       {
@@ -88,7 +88,7 @@ vfprintf (FILE * f, char const *format, va_list ap)
           {
           case '%':
             {
-              fputc (*p, fd);
+              fputc (*p, f);
               count++;
               break;
             }
@@ -96,7 +96,7 @@ vfprintf (FILE * f, char const *format, va_list ap)
             {
               char _c;
               _c = va_arg (ap, long);
-              fputc (_c, fd);
+              fputc (_c, f);
               break;
             }
           case 'd':
@@ -108,7 +108,7 @@ vfprintf (FILE * f, char const *format, va_list ap)
             {
               long d = va_arg (ap, long);
               int base = c == 'o' ? 8 : c == 'x' || c == 'X' ? 16 : 10;
-              char const *s = ntoab (d, base, c != 'u' && c != 'x' && c != 'X');
+              char *s = ntoab (d, base, c != 'u' && c != 'x' && c != 'X');
               if (c == 'X')
                 strupr (s);
               int length = strlen (s);
diff --git a/lib/stdio/vsnprintf.c b/lib/stdio/vsnprintf.c
index 1e3ba4f1..2c224bfe 100644
--- a/lib/stdio/vsnprintf.c
+++ b/lib/stdio/vsnprintf.c
@@ -114,7 +114,7 @@ vsnprintf (char *str, size_t size, char const *format, va_list ap)
             {
               long d = va_arg (ap, long);
               int base = c == 'o' ? 8 : c == 'x' || c == 'X' ? 16 : 10;
-              char const *s = ntoab (d, base, c != 'u' && c != 'x' && c != 'X');
+              char *s = ntoab (d, base, c != 'u' && c != 'x' && c != 'X');
               if (c == 'X')
                 strupr (s);
               int length = strlen (s);
diff --git a/lib/stdlib/__exit.c b/lib/stdlib/__exit.c
index 4eb7c764..a7f41656 100644
--- a/lib/stdlib/__exit.c
+++ b/lib/stdlib/__exit.c
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -18,6 +18,8 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <stdlib.h>
+
 int
 __exit (int status)
 {
diff --git a/lib/stdlib/abort.c b/lib/stdlib/abort.c
index bc93a329..85151442 100644
--- a/lib/stdlib/abort.c
+++ b/lib/stdlib/abort.c
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -18,6 +18,8 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <stdlib.h>
+
 void
 abort (void)
 {
diff --git a/lib/stdlib/mbstowcs.c b/lib/stdlib/mbstowcs.c
index 40dca931..a948544d 100644
--- a/lib/stdlib/mbstowcs.c
+++ b/lib/stdlib/mbstowcs.c
@@ -18,7 +18,9 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <mes/lib.h>
 #include <stdlib.h>
+#include <string.h>
 
 #if !__MESC__
 typedef char wchar_t[];
diff --git a/lib/string/bzero.c b/lib/string/bzero.c
index 54329d67..24de4266 100644
--- a/lib/string/bzero.c
+++ b/lib/string/bzero.c
@@ -21,8 +21,15 @@
 #include <stdlib.h>
 #include <string.h>
 
+#if BZERO_INT
 int
+#else
+void
+#endif
 bzero (void *block, size_t size)
 {
-  return (int) (long) memset (block, 0, size);
+#if BZERO_INT
+  return (int) (long)
+#endif
+    memset (block, 0, size);
 }
diff --git a/lib/string/index.c b/lib/string/index.c
index 9904211b..797b86b0 100644
--- a/lib/string/index.c
+++ b/lib/string/index.c
@@ -20,8 +20,12 @@
 
 #include <string.h>
 
+#if INDEX_INT
 int
+#else
+char *
+#endif
 index (char const *s, int c)
 {
-  return (int) (long) strchr (s, c);
+  return strchr (s, c);
 }
diff --git a/lib/string/rindex.c b/lib/string/rindex.c
index 848fae70..41097cc0 100644
--- a/lib/string/rindex.c
+++ b/lib/string/rindex.c
@@ -20,7 +20,11 @@
 
 #include <string.h>
 
+#if INDEX_INT
 int
+#else
+char *
+#endif
 rindex (char const *s, int c)
 {
   return strrchr (s, c);
diff --git a/lib/string/strcspn.c b/lib/string/strcspn.c
index 4a4ed5e2..e54bf77b 100644
--- a/lib/string/strcspn.c
+++ b/lib/string/strcspn.c
@@ -23,7 +23,7 @@
 size_t
 strcspn (char const *string, char const *stopset)
 {
-  char *p = string;
+  char *p = (char *) string;
   while (*p)
     if (strchr (stopset, *p))
       break;
diff --git a/lib/string/strpbrk.c b/lib/string/strpbrk.c
index 92b0cdb8..57583ee3 100644
--- a/lib/string/strpbrk.c
+++ b/lib/string/strpbrk.c
@@ -23,7 +23,7 @@
 char *
 strpbrk (char const *string, char const *stopset)
 {
-  char *p = string;
+  char *p = (char *) string;
   while (*p)
     if (strchr (stopset, *p))
       break;
diff --git a/lib/stub/frexp.c b/lib/stub/frexp.c
index f26e1aea..7d73724c 100644
--- a/lib/stub/frexp.c
+++ b/lib/stub/frexp.c
@@ -20,7 +20,7 @@
 
 #include <mes/lib.h>
 
-int
+double
 frexp (int x)
 {
   static int stub = 0;