feat(string): complete string.h + strdup/memccpy

src/internal/malloc.h

@@ -0,0 +1,30 @@
+#ifndef VLIBC_INTERNAL_MALLOC_H
+#define VLIBC_INTERNAL_MALLOC_H
+
+/*
+ * vlibc — internal allocator seam (todo 8).
+ *
+ * The allocator todo (#7) owns the real implementation and provides these
+ * entry points; library code that must allocate (strdup, strndup, and later
+ * stdio/regex/...) calls them instead of the public malloc/free so that the
+ * allocator remains the single allocation implementation. The public
+ * malloc/free/calloc/realloc of todo 7 must be backed by the same allocator,
+ * so a block returned by __libc_malloc can be released with public free.
+ *
+ * - __libc_malloc(n): allocate n bytes, 16-byte aligned; NULL + errno ENOMEM
+ *   on failure. May return a unique pointer even when n == 0.
+ * - __libc_free(p): release a block returned by __libc_malloc; NULL is a
+ *   no-op.
+ */
+
+#include <stddef.h>
+
+#include "libc.h"
+
+hidden void *
+__libc_malloc(size_t n); // NOLINT(bugprone-reserved-identifier)
+
+hidden void
+__libc_free(void *p); // NOLINT(bugprone-reserved-identifier)
+
+#endif /* VLIBC_INTERNAL_MALLOC_H */