sandbox/misc/kforth/doc/part-0x09.rst

80 lines
2.8 KiB
ReStructuredText
Raw Normal View History

2018-03-09 21:25:35 +00:00
Write You a Forth, 0x03
-----------------------
:date: 2018-03-09 13:10
:tags: wyaf, forth
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
2018-03-09 23:58:38 +00:00
As usual, the code is tagged with `part-0x09 <https://github.com/kisom/kforth/tree/part-0x09>`_.