diff --git a/libc/upstream-openbsd/lib/libc/stdio/fgets.c b/libc/upstream-openbsd/lib/libc/stdio/fgets.c
index 0ba8770..345884a 100644
--- a/libc/upstream-openbsd/lib/libc/stdio/fgets.c
+++ b/libc/upstream-openbsd/lib/libc/stdio/fgets.c
@@ -43,7 +43,7 @@
  * Do not return NULL if n == 1.
  */
 char *
-fgets(char *buf, int n, FILE *fp)
+fgets(char *buf, int n, FILE *fp) __overloadable
 {
 	size_t len;
 	char *s;
diff --git a/libc/upstream-openbsd/lib/libc/stdio/fwrite.c b/libc/upstream-openbsd/lib/libc/stdio/fwrite.c
index f0a17bf..c72d968 100644
--- a/libc/upstream-openbsd/lib/libc/stdio/fwrite.c
+++ b/libc/upstream-openbsd/lib/libc/stdio/fwrite.c
@@ -45,7 +45,7 @@
  * Return the number of whole objects written.
  */
 size_t
-fwrite(const void *buf, size_t size, size_t count, FILE *fp)
+fwrite(const void *buf, size_t size, size_t count, FILE *fp) __overloadable
 {
 	size_t n;
 	struct __suio uio;
diff --git a/libc/upstream-openbsd/lib/libc/string/memchr.c b/libc/upstream-openbsd/lib/libc/string/memchr.c
index 4573e3c..05a1197 100644
--- a/libc/upstream-openbsd/lib/libc/string/memchr.c
+++ b/libc/upstream-openbsd/lib/libc/string/memchr.c
@@ -34,8 +34,7 @@
 #include <string.h>
 
 void *
-memchr(const void *s, int c, size_t n)
-{
+memchr(const void *s, int c, size_t n) __overloadable {
 	if (n != 0) {
 		const unsigned char *p = s;
 
diff --git a/libc/upstream-openbsd/lib/libc/string/memmove.c b/libc/upstream-openbsd/lib/libc/string/memmove.c
index 1baad53..910f48c 100644
--- a/libc/upstream-openbsd/lib/libc/string/memmove.c
+++ b/libc/upstream-openbsd/lib/libc/string/memmove.c
@@ -46,7 +46,7 @@
  * Copy a block of memory, handling overlap.
  */
 void *
-memmove(void *dst0, const void *src0, size_t length)
+memmove(void *dst0, const void *src0, size_t length) __overloadable
 {
 	char *dst = dst0;
 	const char *src = src0;
diff --git a/libc/upstream-openbsd/lib/libc/string/memrchr.c b/libc/upstream-openbsd/lib/libc/string/memrchr.c
index bd27ebc..1cce809 100644
--- a/libc/upstream-openbsd/lib/libc/string/memrchr.c
+++ b/libc/upstream-openbsd/lib/libc/string/memrchr.c
@@ -23,7 +23,7 @@
  * Find the last occurrence of 'c' in the buffer 's' of size 'n'.
  */
 void *
-memrchr(const void *s, int c, size_t n)
+memrchr(const void *s, int c, size_t n) __overloadable
 {
 	const unsigned char *cp;
 
diff --git a/libc/upstream-openbsd/lib/libc/string/stpcpy.c b/libc/upstream-openbsd/lib/libc/string/stpcpy.c
index d88afac..3ed5782 100644
--- a/libc/upstream-openbsd/lib/libc/string/stpcpy.c
+++ b/libc/upstream-openbsd/lib/libc/string/stpcpy.c
@@ -37,7 +37,7 @@
 #endif
 
 char *
-stpcpy(char *to, const char *from)
+stpcpy(char *to, const char *from) __overloadable
 {
 	for (; (*to = *from) != '\0'; ++from, ++to);
 	return(to);
diff --git a/libc/upstream-openbsd/lib/libc/string/stpncpy.c b/libc/upstream-openbsd/lib/libc/string/stpncpy.c
index c7c2a57..661a4fd 100644
--- a/libc/upstream-openbsd/lib/libc/string/stpncpy.c
+++ b/libc/upstream-openbsd/lib/libc/string/stpncpy.c
@@ -35,7 +35,7 @@
 #include <string.h>
 
 char *
-stpncpy(char *dst, const char *src, size_t n)
+stpncpy(char *dst, const char *src, size_t n) __overloadable
 {
 	if (n != 0) {
 		char *d = dst;
diff --git a/libc/upstream-openbsd/lib/libc/string/strcat.c b/libc/upstream-openbsd/lib/libc/string/strcat.c
index 646c9c2..7872a2d 100644
--- a/libc/upstream-openbsd/lib/libc/string/strcat.c
+++ b/libc/upstream-openbsd/lib/libc/string/strcat.c
@@ -37,7 +37,7 @@
 #endif
 
 char *
-strcat(char *s, const char *append)
+strcat(char *s, const char *append) __overloadable
 {
 	char *save = s;
 
diff --git a/libc/upstream-openbsd/lib/libc/string/strcpy.c b/libc/upstream-openbsd/lib/libc/string/strcpy.c
index 5a9001e..1b1169c 100644
--- a/libc/upstream-openbsd/lib/libc/string/strcpy.c
+++ b/libc/upstream-openbsd/lib/libc/string/strcpy.c
@@ -37,7 +37,7 @@
 #endif
 
 char *
-strcpy(char *to, const char *from)
+strcpy(char *to, const char *from) __overloadable
 {
 	char *save = to;
 
diff --git a/libc/upstream-openbsd/lib/libc/string/strlcat.c b/libc/upstream-openbsd/lib/libc/string/strlcat.c
index 073b0d4..7bf98aa 100644
--- a/libc/upstream-openbsd/lib/libc/string/strlcat.c
+++ b/libc/upstream-openbsd/lib/libc/string/strlcat.c
@@ -27,7 +27,7 @@
  * If retval >= dsize, truncation occurred.
  */
 size_t
-strlcat(char *dst, const char *src, size_t dsize)
+strlcat(char *dst, const char *src, size_t dsize) __overloadable
 {
 	const char *odst = dst;
 	const char *osrc = src;
diff --git a/libc/upstream-openbsd/lib/libc/string/strlcpy.c b/libc/upstream-openbsd/lib/libc/string/strlcpy.c
index 5fcf084..a5343b8 100644
--- a/libc/upstream-openbsd/lib/libc/string/strlcpy.c
+++ b/libc/upstream-openbsd/lib/libc/string/strlcpy.c
@@ -25,7 +25,7 @@
  * Returns strlen(src); if retval >= dsize, truncation occurred.
  */
 size_t
-strlcpy(char *dst, const char *src, size_t dsize)
+strlcpy(char *dst, const char *src, size_t dsize) __overloadable
 {
 	const char *osrc = src;
 	size_t nleft = dsize;
diff --git a/libc/upstream-openbsd/lib/libc/string/strncat.c b/libc/upstream-openbsd/lib/libc/string/strncat.c
index c4df4f2..32334b3 100644
--- a/libc/upstream-openbsd/lib/libc/string/strncat.c
+++ b/libc/upstream-openbsd/lib/libc/string/strncat.c
@@ -38,7 +38,7 @@
  * are written at dst (at most n+1 bytes being appended).  Return dst.
  */
 char *
-strncat(char *dst, const char *src, size_t n)
+strncat(char *dst, const char *src, size_t n) __overloadable
 {
 	if (n != 0) {
 		char *d = dst;
diff --git a/libc/upstream-openbsd/lib/libc/string/strncpy.c b/libc/upstream-openbsd/lib/libc/string/strncpy.c
index 5003a19..e83c7e5 100644
--- a/libc/upstream-openbsd/lib/libc/string/strncpy.c
+++ b/libc/upstream-openbsd/lib/libc/string/strncpy.c
@@ -39,7 +39,7 @@
  * Return dst.
  */
 char *
-strncpy(char *dst, const char *src, size_t n)
+strncpy(char *dst, const char *src, size_t n) __overloadable
 {
 	if (n != 0) {
 		char *d = dst;