Paul Brook writes:

When building an arm-uclinux toolchain withthreading disabled I get:

libc/stdio/getchar.c:26: error: 'getchar' aliased to undefined 
symbol 'getchar_unlocked'

It looks like it's missing libc_hidden_def(getchar_unlocked). Patch below 
fixes this.

libc/stdio/getchar.c

@@ -21,6 +21,7 @@ int getchar_unlocked(void)
 
 	return __GETC_UNLOCKED_MACRO(stream);
 }
+libc_hidden_def(getchar_unlocked)
 
 #ifndef __UCLIBC_HAS_THREADS__
 strong_alias(getchar_unlocked,getchar)