Add simple memcpy, memcmp and memset functions for nolibc.

lib/std/core/mem.c3

@@ -778,3 +778,41 @@ fn void* trealloc(void* ptr, usz size, usz alignment = mem::DEFAULT_MEM_ALIGNMEN
 	return allocator::temp().resize(ptr, size, alignment)!!;
 }
 
+module std::core::mem @if(env::NO_LIBC);
+
+fn CInt __memcmp(void* s1, void* s2, usz n) @weak @export("memcmp")
+{
+	char* p1 = s1;
+	char* p2 = s2;
+	for (usz i = 0; i < n; i++, p1++, p2++)
+	{
+		char c1 = *p1;
+		char c2 = *p2;
+		if (c1 < c2) return -1;
+		if (c1 > c2) return 1;
+	}
+	return 0;
+}
+
+fn void* __memset(void* str, CInt c, usz n) @weak @export("memset")
+{
+	char* p = str;
+	char cc = (char)c;
+	for (usz i = 0; i < n; i++, p++)
+	{
+		*p = cc;
+	}
+	return str;
+}
+
+fn void* __memcpy(void* dst, void* src, usz n) @weak @export("memcpy")
+{
+	char* d = dst;
+	char* s = src;
+	for (usz i = 0; i < n; i++, d++, s++)
+	{
+		*d = *s;
+	}
+	return dst;
+}
+