diff --git a/libc/bionic/pthread_attr.cpp b/libc/bionic/pthread_attr.cpp
index fdf296591..d597c7e29 100644
--- a/libc/bionic/pthread_attr.cpp
+++ b/libc/bionic/pthread_attr.cpp
@@ -94,18 +94,21 @@ int pthread_attr_getstacksize(const pthread_attr_t* attr, size_t* stack_size) {
   return 0;
 }
 
-int pthread_attr_setstackaddr(pthread_attr_t*, void*) {
+#if !defined(__LP64__)
+// TODO: this exists only for backward binary compatibility on 32 bit platforms.
+extern "C" int pthread_attr_setstackaddr(pthread_attr_t*, void*) {
   // This was removed from POSIX.1-2008, and is not implemented on bionic.
   // Needed for ABI compatibility with the NDK.
   return ENOSYS;
 }
 
-int pthread_attr_getstackaddr(const pthread_attr_t* attr, void** stack_addr) {
+extern "C" int pthread_attr_getstackaddr(const pthread_attr_t* attr, void** stack_addr) {
   // This was removed from POSIX.1-2008.
   // Needed for ABI compatibility with the NDK.
   *stack_addr = (char*)attr->stack_base + attr->stack_size;
   return 0;
 }
+#endif // !defined(__LP64__)
 
 int pthread_attr_setstack(pthread_attr_t* attr, void* stack_base, size_t stack_size) {
   if ((stack_size & (PAGE_SIZE - 1) || stack_size < PTHREAD_STACK_MIN)) {
diff --git a/libc/bionic/pthread_cond.cpp b/libc/bionic/pthread_cond.cpp
index 213bcd733..c09e9728a 100644
--- a/libc/bionic/pthread_cond.cpp
+++ b/libc/bionic/pthread_cond.cpp
@@ -206,14 +206,14 @@ extern "C" int pthread_cond_timedwait_monotonic(pthread_cond_t* cond, pthread_mu
 extern "C" int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
   return __pthread_cond_timedwait(cond, mutex, abstime, CLOCK_MONOTONIC);
 }
-#endif // !defined(__LP64__)
 
-int pthread_cond_timedwait_relative_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) {
+extern "C" int pthread_cond_timedwait_relative_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) {
   return __pthread_cond_timedwait_relative(cond, mutex, reltime);
 }
 
-int pthread_cond_timeout_np(pthread_cond_t* cond, pthread_mutex_t* mutex, unsigned ms) {
+extern "C" int pthread_cond_timeout_np(pthread_cond_t* cond, pthread_mutex_t* mutex, unsigned ms) {
   timespec ts;
   timespec_from_ms(ts, ms);
   return __pthread_cond_timedwait_relative(cond, mutex, &ts);
 }
+#endif // !defined(__LP64__)