diff --git a/Makefile b/Makefile
index aeed4bc59..e502082a3 100644
--- a/Makefile
+++ b/Makefile
@@ -32,7 +32,8 @@ endif
 # These variables describe the locations of various files and
 # directories in the source tree.
 BASICS_DIR = $(CURDIR)/basics
-BASICS_INC = $(BASICS_DIR)/include
+BASICS_HEADERS_PUBLIC = $(BASICS_DIR)/headers/public
+BASICS_HEADERS_PRIVATE = $(BASICS_DIR)/headers/private
 BASICS_CRT1_SOURCE = $(BASICS_DIR)/crt/crt1.c
 BASICS_SOURCES = $(wildcard $(BASICS_DIR)/sources/*.c)
 DLMALLOC_DIR = $(CURDIR)/dlmalloc
@@ -300,7 +301,7 @@ include_dirs:
 	# Install the include files.
 	#
 	mkdir -p "$(SYSROOT_INC)"
-	cp -r "$(BASICS_INC)" "$(SYSROOT)"
+	cp -r "$(BASICS_HEADERS_PUBLIC)"/* "$(SYSROOT_INC)"
 	cp -r "$(LIBC_BOTTOM_HALF_HEADERS_PUBLIC)"/* "$(SYSROOT_INC)"
 
 	# Generate musl's bits/alltypes.h header.
@@ -417,8 +418,10 @@ startup_files: include_dirs
 	# Build the startup files.
 	#
 	mkdir -p "$(SYSROOT_LIB)"
-	"$(WASM_CC)" $(WASM_CFLAGS) -c $(CRT1_SOURCE) -MD -MP -o $(SYSROOT_LIB)/crt1.o
-	"$(WASM_CC)" $(WASM_CFLAGS) -c $(CRT1_SOURCE) -MD -MP -DREACTOR_RUNTIME -o $(SYSROOT_LIB)/reactor-crt1.o
+	"$(WASM_CC)" $(WASM_CFLAGS) -I$(BASICS_HEADERS_PRIVATE) -c \
+	    $(CRT1_SOURCE) -MD -MP -o $(SYSROOT_LIB)/crt1.o
+	"$(WASM_CC)" $(WASM_CFLAGS) -I$(BASICS_HEADERS_PRIVATE) -c \
+	    $(CRT1_SOURCE) -MD -MP -DREACTOR_RUNTIME -o $(SYSROOT_LIB)/reactor-crt1.o
 
 libc: include_dirs \
     $(SYSROOT_LIB)/libc.a \
diff --git a/basics/crt/crt1.c b/basics/crt/crt1.c
index fb3fdb444..c228381fe 100644
--- a/basics/crt/crt1.c
+++ b/basics/crt/crt1.c
@@ -1,34 +1,20 @@
-extern void __wasm_call_ctors(void);
-void _Exit(int) __attribute__((noreturn));
-
-#ifdef REACTOR_RUNTIME
-extern void reactor_setup(int, char *[]);
-#else
-extern int main(int, char *[]);
-extern void __prepare_for_exit(void);
-#endif
+#include "crt1.h"
 
 #ifdef REACTOR_RUNTIME
 void __wasi_unstable_reactor_start(void) {
 #else
 void _start(void) {
 #endif
-    /* The linker synthesizes this to call constructors. */
-    __wasm_call_ctors();
+    /*
+     * In the basics directory, we don't have a way to pass in command-line
+     * parameters, so we just use some simple placeholder arguments. For real
+     * command-line argument handling, see the crt1.c in libc-bottom-half.
+     */
+    static char *argv[] = {
+        "program",
+        NULL
+    };
 
-#ifdef REACTOR_RUNTIME
-    /* Call reactor_setup with the arguments. */
-    reactor_setup(argc, argv);
-#else
-    /* Call main with no arguments. */
-    int r = main(0, 0);
-
-    /* Call atexit functions, destructors, stdio cleanup, etc. */
-    __prepare_for_exit();
-
-    /* If main exited successfully, just return, otherwise call _Exit. */
-    if (r != 0) {
-        _Exit(r);
-    }
-#endif
+    /* Start the program! */
+    start_program(1, argv);
 }
diff --git a/basics/headers/private/crt1.h b/basics/headers/private/crt1.h
new file mode 100644
index 000000000..8105816c5
--- /dev/null
+++ b/basics/headers/private/crt1.h
@@ -0,0 +1,40 @@
+/*
+ * Common code for defining the crt1.o object, which defines the program
+ * entrypoint.
+ */
+
+extern void __wasm_call_ctors(void);
+void _Exit(int) __attribute__((noreturn));
+
+#ifdef REACTOR_RUNTIME
+extern void reactor_setup(int, char *[]) __attribute__((weak));
+#else
+extern int main(int, char *[]);
+extern void __prepare_for_exit(void);
+#endif
+
+static inline void start_program(int argc, char *argv[]) {
+    /* The linker synthesizes this to call constructors. */
+    __wasm_call_ctors();
+
+#ifdef REACTOR_RUNTIME
+    /*
+     * Call reactor_setup with the arguments. It's a weak external, so we
+     * can skip calling it if it's not defined.
+     */
+    if (reactor_setup) {
+        reactor_setup(argc, argv);
+    }
+#else
+    /* Call main with no arguments. */
+    int r = main(0, 0);
+
+    /* Call atexit functions, destructors, stdio cleanup, etc. */
+    __prepare_for_exit();
+
+    /* If main exited successfully, just return, otherwise call _Exit. */
+    if (r != 0) {
+        _Exit(r);
+    }
+#endif
+}
diff --git a/basics/include/__errno.h b/basics/headers/public/__errno.h
similarity index 100%
rename from basics/include/__errno.h
rename to basics/headers/public/__errno.h
diff --git a/basics/include/__functions_malloc.h b/basics/headers/public/__functions_malloc.h
similarity index 100%
rename from basics/include/__functions_malloc.h
rename to basics/headers/public/__functions_malloc.h
diff --git a/basics/include/__functions_memcpy.h b/basics/headers/public/__functions_memcpy.h
similarity index 100%
rename from basics/include/__functions_memcpy.h
rename to basics/headers/public/__functions_memcpy.h
diff --git a/basics/include/__header_inttypes.h b/basics/headers/public/__header_inttypes.h
similarity index 100%
rename from basics/include/__header_inttypes.h
rename to basics/headers/public/__header_inttypes.h
diff --git a/basics/include/__macro_PAGESIZE.h b/basics/headers/public/__macro_PAGESIZE.h
similarity index 100%
rename from basics/include/__macro_PAGESIZE.h
rename to basics/headers/public/__macro_PAGESIZE.h
diff --git a/basics/include/__struct_stat.h b/basics/headers/public/__struct_stat.h
similarity index 100%
rename from basics/include/__struct_stat.h
rename to basics/headers/public/__struct_stat.h
diff --git a/basics/include/__struct_timespec.h b/basics/headers/public/__struct_timespec.h
similarity index 100%
rename from basics/include/__struct_timespec.h
rename to basics/headers/public/__struct_timespec.h
diff --git a/basics/include/__typedef_blkcnt_t.h b/basics/headers/public/__typedef_blkcnt_t.h
similarity index 100%
rename from basics/include/__typedef_blkcnt_t.h
rename to basics/headers/public/__typedef_blkcnt_t.h
diff --git a/basics/include/__typedef_blksize_t.h b/basics/headers/public/__typedef_blksize_t.h
similarity index 100%
rename from basics/include/__typedef_blksize_t.h
rename to basics/headers/public/__typedef_blksize_t.h
diff --git a/basics/include/__typedef_clock_t.h b/basics/headers/public/__typedef_clock_t.h
similarity index 100%
rename from basics/include/__typedef_clock_t.h
rename to basics/headers/public/__typedef_clock_t.h
diff --git a/basics/include/__typedef_dev_t.h b/basics/headers/public/__typedef_dev_t.h
similarity index 100%
rename from basics/include/__typedef_dev_t.h
rename to basics/headers/public/__typedef_dev_t.h
diff --git a/basics/include/__typedef_gid_t.h b/basics/headers/public/__typedef_gid_t.h
similarity index 100%
rename from basics/include/__typedef_gid_t.h
rename to basics/headers/public/__typedef_gid_t.h
diff --git a/basics/include/__typedef_ino_t.h b/basics/headers/public/__typedef_ino_t.h
similarity index 100%
rename from basics/include/__typedef_ino_t.h
rename to basics/headers/public/__typedef_ino_t.h
diff --git a/basics/include/__typedef_mode_t.h b/basics/headers/public/__typedef_mode_t.h
similarity index 100%
rename from basics/include/__typedef_mode_t.h
rename to basics/headers/public/__typedef_mode_t.h
diff --git a/basics/include/__typedef_nlink_t.h b/basics/headers/public/__typedef_nlink_t.h
similarity index 100%
rename from basics/include/__typedef_nlink_t.h
rename to basics/headers/public/__typedef_nlink_t.h
diff --git a/basics/include/__typedef_off_t.h b/basics/headers/public/__typedef_off_t.h
similarity index 100%
rename from basics/include/__typedef_off_t.h
rename to basics/headers/public/__typedef_off_t.h
diff --git a/basics/include/__typedef_ssize_t.h b/basics/headers/public/__typedef_ssize_t.h
similarity index 100%
rename from basics/include/__typedef_ssize_t.h
rename to basics/headers/public/__typedef_ssize_t.h
diff --git a/basics/include/__typedef_suseconds_t.h b/basics/headers/public/__typedef_suseconds_t.h
similarity index 100%
rename from basics/include/__typedef_suseconds_t.h
rename to basics/headers/public/__typedef_suseconds_t.h
diff --git a/basics/include/__typedef_time_t.h b/basics/headers/public/__typedef_time_t.h
similarity index 100%
rename from basics/include/__typedef_time_t.h
rename to basics/headers/public/__typedef_time_t.h
diff --git a/basics/include/__typedef_uid_t.h b/basics/headers/public/__typedef_uid_t.h
similarity index 100%
rename from basics/include/__typedef_uid_t.h
rename to basics/headers/public/__typedef_uid_t.h
diff --git a/basics/include/errno.h b/basics/headers/public/errno.h
similarity index 100%
rename from basics/include/errno.h
rename to basics/headers/public/errno.h
diff --git a/basics/include/inttypes.h b/basics/headers/public/inttypes.h
similarity index 100%
rename from basics/include/inttypes.h
rename to basics/headers/public/inttypes.h
diff --git a/basics/include/stdlib.h b/basics/headers/public/stdlib.h
similarity index 100%
rename from basics/include/stdlib.h
rename to basics/headers/public/stdlib.h
diff --git a/basics/include/string.h b/basics/headers/public/string.h
similarity index 100%
rename from basics/include/string.h
rename to basics/headers/public/string.h
diff --git a/basics/include/sys/stat.h b/basics/headers/public/sys/stat.h
similarity index 100%
rename from basics/include/sys/stat.h
rename to basics/headers/public/sys/stat.h
diff --git a/basics/include/sys/types.h b/basics/headers/public/sys/types.h
similarity index 100%
rename from basics/include/sys/types.h
rename to basics/headers/public/sys/types.h
diff --git a/basics/include/time.h b/basics/headers/public/time.h
similarity index 100%
rename from basics/include/time.h
rename to basics/headers/public/time.h
diff --git a/basics/include/wchar.h b/basics/headers/public/wchar.h
similarity index 100%
rename from basics/include/wchar.h
rename to basics/headers/public/wchar.h
diff --git a/expected/wasm32-wasi/undefined-symbols.txt b/expected/wasm32-wasi/undefined-symbols.txt
index 33c9ec3b3..75bee0304 100644
--- a/expected/wasm32-wasi/undefined-symbols.txt
+++ b/expected/wasm32-wasi/undefined-symbols.txt
@@ -68,4 +68,3 @@ __wasi_sock_send
 __wasi_sock_shutdown
 __wasm_call_ctors
 main
-reactor_setup
diff --git a/libc-bottom-half/crt/crt1.c b/libc-bottom-half/crt/crt1.c
index 686380184..f99ad8923 100644
--- a/libc-bottom-half/crt/crt1.c
+++ b/libc-bottom-half/crt/crt1.c
@@ -1,18 +1,9 @@
+#include "crt1.h"
 #include <stdlib.h>
 #include <sysexits.h>
 #include <wasi/core.h>
 #include <wasi/libc.h>
-
 extern char **__environ;
-extern void __wasm_call_ctors(void);
-void _Exit(int) __attribute__((noreturn));
-
-#ifdef REACTOR_RUNTIME
-extern void reactor_setup(int, char *[]);
-#else
-extern int main(int, char *[]);
-extern void __prepare_for_exit(void);
-#endif
 
 static __wasi_errno_t populate_args(size_t *argc, char ***argv) {
     __wasi_errno_t err;
@@ -131,22 +122,6 @@ void _start(void) {
         _Exit(EX_OSERR);
     }
 
-    /* The linker synthesizes this to call constructors. */
-    __wasm_call_ctors();
-
-#ifdef REACTOR_RUNTIME
-    /* Call reactor_setup with the arguments. */
-    reactor_setup(argc, argv);
-#else
-    /* Call main with the arguments. */
-    int r = main(argc, argv);
-
-    /* Call atexit functions, destructors, stdio cleanup, etc. */
-    __prepare_for_exit();
-
-    /* If main exited successfully, just return, otherwise call _Exit. */
-    if (r != 0) {
-        _Exit(r);
-    }
-#endif
+    /* Start the program! */
+    start_program(argc, argv);
 }