devlogs : Write You a Forth, 0x09

So the last post had some issues and I hadn't updated the front end to use the new tooling. I removed the arena and switched to the internal dictionary:

#include "defs.h"
#include "eval.h"
#include "stack.h"
#include "word.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void
hello(void)
{
        printf("hello, world\n");
}

int
main(void)
{
        dstack_push(2);
        dstack_push(3);

        append_native_word("hello", 5, hello);
        uintptr_t       hwb = 0;

        if (!lookup("hello", 5, &hwb)) {
                fprintf(stderr, "failed to lookup 'hello'\n");
                exit(1);
        }
        printf("hello: 0x%lx\n", (unsigned long)hwb);
        if (!execute("hello", 5)) {
                fprintf(stderr, "failed to execute 'hello'\n");
                exit(1);
        }

        printf("finished\n");
}

Also, there's a (not-so) subtle bug in word.c: the header is overwritten by the function body, which is the path to segfaulting. I've also added an offset variable to make tracking the offset easier:

void
store_native(uint8_t *entry, const char *name, const uint8_t len, void(*target)(void))
{
        uintptr_t       target_p = (uintptr_t)target;
-       size_t          link = 2 + len + (2 * sizeof(uintptr_t));
+       size_t          offset = 2 + len + sizeof(size_t);
+       size_t          link = offset + (2 * sizeof(uintptr_t));

        /* write the header */
        entry[0] = len;
@@ -45,8 +66,9 @@ store_native(uint8_t *entry, const char *name, const uint8_t len, void(*target)(
        memcpy(entry+2+len, &link, sizeof(link));

        /* write the native executor codeword and the function pointer */
-       memcpy(entry, (uint8_t *)(&nexec_p), sizeof(uintptr_t));
-       memcpy(entry + sizeof(uintptr_t), (uint8_t *)(&target_p), sizeof(uintptr_t));
+       memcpy(entry+offset, (uint8_t *)(&nexec_p), sizeof(uintptr_t));
+       offset += sizeof(uintptr_t);
+       memcpy(entry+offset, (uint8_t *)(&target_p), sizeof(uintptr_t));
}

The header file word.h didn't contain append_native_word, lookup, or execute, so that gets updated too. The end result is:

$ ./kf-default
hello: 0x6cbc6f
hello, world
finished

As usual, the code is tagged with part-0x09.

Tags: forth, wyaf