add simple sum example

examples/stubs.c

@@ -0,0 +1,78 @@
+#include <stddef.h>
+#include <stdint.h>
+
+// https://git.musl-libc.org/cgit/musl/tree/src/string/memcpy.c
+
+void *memcpy(void *restrict dest, const void *restrict src, size_t n) {
+  unsigned char *d = dest;
+  const unsigned char *s = src;
+
+  for (; n; n--)
+    *d++ = *s++;
+  return dest;
+}
+
+// https://git.musl-libc.org/cgit/musl/tree/src/string/memmove.c
+
+void *memmove(void *dest, const void *src, size_t n) {
+  char *d = dest;
+  const char *s = src;
+
+  if (d == s)
+    return d;
+  if ((uintptr_t)s - (uintptr_t)d - n <= -2 * n)
+    return memcpy(d, s, n);
+
+  if (d < s) {
+    for (; n; n--)
+      *d++ = *s++;
+  } else {
+    while (n)
+      n--, d[n] = s[n];
+  }
+
+  return dest;
+}
+
+// https://git.musl-libc.org/cgit/musl/tree/src/string/memset.c
+
+void *memset(void *dest, int c, size_t n) {
+  unsigned char *s = dest;
+  size_t k;
+
+  /* Fill head and tail with minimal branching. Each
+   * conditional ensures that all the subsequently used
+   * offsets are well-defined and in the dest region. */
+
+  if (!n)
+    return dest;
+  s[0] = c;
+  s[n - 1] = c;
+  if (n <= 2)
+    return dest;
+  s[1] = c;
+  s[2] = c;
+  s[n - 2] = c;
+  s[n - 3] = c;
+  if (n <= 6)
+    return dest;
+  s[3] = c;
+  s[n - 4] = c;
+  if (n <= 8)
+    return dest;
+
+  /* Advance pointer to align it at a 4-byte boundary,
+   * and truncate n to a multiple of 4. The previous code
+   * already took care of any head/tail that get cut off
+   * by the alignment. */
+
+  k = -(uintptr_t)s & 3;
+  s += k;
+  n -= k;
+  n &= -4;
+
+  for (; n; n--, s++)
+    *s = c;
+
+  return dest;
+}