feat: abstract I/O and strings for freestanding compilation

Co-authored-by: aider (openrouter/moonshotai/kimi-k2.6) <aider@aider.chat>

Makefile

@@ -1,19 +1,22 @@
-CC = gcc
+CC = clang
-CFLAGS = -Wall -Wextra -g -std=c11 -D_POSIX_C_SOURCE=200809L
+CFLAGS = -Wall -Wextra -g -std=c11
-LDFLAGS =
+COMMON_SRCS = forth_core.c forth_dict.c forth_words.c forth_interp.c main.c
-SRCS = forth_core.c forth_dict.c forth_words.c forth_interp.c main.c
+
-OBJS = $(SRCS:.c=.o)
+HOSTED_SRCS = $(COMMON_SRCS) platform_hosted.c
+FREESTANDING_SRCS = $(COMMON_SRCS) platform_freestanding.c
+
 TARGET = forth
+FREESTANDING_TARGET = forth_freestanding
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS)
+$(TARGET): $(HOSTED_SRCS) forth.h
-	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+	$(CC) $(CFLAGS) -D_POSIX_C_SOURCE=200809L -o $@ $(HOSTED_SRCS)
 
-%.o: %.c forth.h
+$(FREESTANDING_TARGET): $(FREESTANDING_SRCS) forth.h
-	$(CC) $(CFLAGS) -c $< -o $@
+	$(CC) $(CFLAGS) -ffreestanding -nostdlib -fno-stack-protector -o $@ $(FREESTANDING_SRCS)
 
 clean:
-	rm -f $(OBJS) $(TARGET)
+	rm -f $(TARGET) $(FREESTANDING_TARGET)
 
 .PHONY: all clean

forth.h

@@ -1,29 +1,46 @@
 #ifndef FORTH_H
 #define FORTH_H
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <ctype.h>
 #include <stdint.h>
-#include <inttypes.h>
+#include <stddef.h>
+#include <stdarg.h>
 
 // Configuration (all hard limits removed)
 #define MAX_NAME_LEN 31
+#define FORTH_EOF (-1)
 
-/* Portable panic hook. Override for bare-metal reset/handling. */
+/* Platform interface -- must be provided by the target platform layer. */
-#ifndef forth_panic
+void forth_putchar(char c);
-#define forth_panic() do { for (;;) ; } while (0)
+int forth_getchar(void);
-#endif
+void forth_printf(const char* fmt, ...);
+void forth_fflush(void);
+void forth_panic(void);
 
-/* Portable I/O hooks. Define FORTH_CUSTOM_IO before including this header
+/* Platform string-to-number (base 10 is required). */
- * to provide bare-metal UART (or other) implementations. */
+int64_t forth_strtoll(const char* str, char** endptr, int base);
-#ifndef FORTH_CUSTOM_IO
+
-#define forth_putchar(c) putchar(c)
+/* Portable character classification. */
-#define forth_getchar() getchar()
+static inline int forth_isspace(int c) {
-#define forth_printf(...) printf(__VA_ARGS__)
+    return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v';
-#define forth_fflush() fflush(stdout)
+}
-#endif
+
+/* Portable string operations. */
+static inline size_t forth_strlen(const char* s) {
+    size_t n = 0;
+    while (s[n]) n++;
+    return n;
+}
+
+static inline void forth_memcpy(void* dst, const void* src, size_t n) {
+    char* d = dst;
+    const char* s = src;
+    while (n--) *d++ = *s++;
+}
+
+static inline int forth_strcmp(const char* a, const char* b) {
+    while (*a && *a == *b) { a++; b++; }
+    return (unsigned char)*a - (unsigned char)*b;
+}
 
 /* Static memory sizes (override before including forth.h) */
 #ifndef FORTH_DATA_STACK_SIZE
@@ -105,6 +122,9 @@ extern Word* w_branch;
 extern Word* w_zbranch;
 extern Word* w_dot_quote_inner;
 
+// Entry point
+void forth_run(void);
+
 // Core function prototypes
 void data_push(int64_t val);
 int64_t data_pop(void);

forth_dict.c

@@ -5,10 +5,10 @@ Word* add_primitive(const char* name, void (*code)(Word*), uint8_t flags) {
     w->prev = dict_head;
     dict_head = w;
 
-    size_t len = strlen(name);
+    size_t len = forth_strlen(name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
     w->flags = flags | (uint8_t)len;
-    memcpy(w->name, name, len);
+    forth_memcpy(w->name, name, len);
     w->name[len] = '\0';
     w->code = code;
     w->body = NULL;
@@ -18,14 +18,14 @@ Word* add_primitive(const char* name, void (*code)(Word*), uint8_t flags) {
 Word* lookup_word(const char* name) {
     for (Word* w = dict_head; w != NULL; w = w->prev) {
         if (w->flags & (1 << 6)) continue;
-        if (strcmp(w->name, name) == 0) return w;
+        if (forth_strcmp(w->name, name) == 0) return w;
     }
     return NULL;
 }
 
 Word* lookup_word_internal(const char* name) {
     for (Word* w = dict_head; w != NULL; w = w->prev) {
-        if (strcmp(w->name, name) == 0) return w;
+        if (forth_strcmp(w->name, name) == 0) return w;
     }
     return NULL;
 }

forth_interp.c

@@ -3,7 +3,7 @@
 // Input tokenizer (unchanged)
 char* next_token(void) {
     if (input_ptr == NULL) return NULL;
-    while (*input_ptr != '\0' && isspace((unsigned char)*input_ptr)) {
+    while (*input_ptr != '\0' && forth_isspace((unsigned char)*input_ptr)) {
         input_ptr++;
     }
     if (*input_ptr == '\0') return NULL;
@@ -63,10 +63,10 @@ void process_token(const char* token) {
         }
     } else { // Try to parse as number
         char* end;
-        long long v = strtoll(token, &end, 10);
+        int64_t v = forth_strtoll(token, &end, 10);
         if (end != token && *end == '\0') {
             if (state == 0) {
-                data_push((int64_t)v);
+                data_push(v);
             } else { // Compile lit + number
                 if (!w_lit) {
                     forth_printf("Fatal: lit word not found\n");
@@ -91,13 +91,13 @@ void outer_interpreter(void) {
         int c;
         while (i < sizeof(line_buf) - 1) {
             c = forth_getchar();
-            if (c == EOF || c == '\n' || c == '\r') {
+            if (c == FORTH_EOF || c == '\n' || c == '\r') {
                 break;
             }
             line_buf[i++] = (char)c;
         }
         line_buf[i] = '\0';
-        if (i == 0 && c == EOF) {
+        if (i == 0 && c == FORTH_EOF) {
             break;
         }
         input_buf = line_buf;

forth_words.c

@@ -309,7 +309,7 @@ void do_zero_gt(Word* w) {
 void do_dot(Word* w) {
     (void)w;
     if (data_sp < 0) return;
-    forth_printf("%" PRId64 " ", data_pop());
+    forth_printf("%lld ", (long long)data_pop());
     forth_fflush();
 }
 
@@ -329,7 +329,7 @@ void do_emit(Word* w) {
 void do_key(Word* w) {
     (void)w;
     int c = forth_getchar();
-    data_push(c == EOF ? -1 : c);
+    data_push(c == FORTH_EOF ? -1 : c);
 }
 
 void do_dot_quote(Word* w) {
@@ -337,7 +337,7 @@ void do_dot_quote(Word* w) {
     if (state == 0) {
         // Interpret mode: print immediately
         if (input_ptr == NULL) { forth_printf("Missing string\n"); return; }
-        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
+        while (*input_ptr && forth_isspace((unsigned char)*input_ptr)) input_ptr++;
         if (*input_ptr != '"') { forth_printf("Expected \" to start string\n"); return; }
         input_ptr++;
         char* start = input_ptr;
@@ -349,7 +349,7 @@ void do_dot_quote(Word* w) {
     } else {
         // Compile mode: compile string for runtime
         if (input_ptr == NULL) { forth_printf("Missing string\n"); return; }
-        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
+        while (*input_ptr && forth_isspace((unsigned char)*input_ptr)) input_ptr++;
         if (*input_ptr != '"') { forth_printf("Expected \" to start string\n"); return; }
         input_ptr++;
         char* start = input_ptr;

main.c

@@ -1,6 +1,6 @@
 #include "forth.h"
 
-int main(void) {
+void forth_run(void) {
     here = user_mem;
 
     // Hidden words first
@@ -104,5 +104,4 @@ int main(void) {
 
     // Start outer interpreter
     outer_interpreter();
-    return 0;
 }

platform_freestanding.c

@@ -0,0 +1,114 @@
+#include "forth.h"
+#include <stdarg.h>
+
+static inline long syscall3(long n, long a1, long a2, long a3) {
+    long ret;
+    __asm__ volatile ("syscall"
+        : "=a"(ret)
+        : "a"(n), "D"(a1), "S"(a2), "d"(a3)
+        : "rcx", "r11", "memory");
+    return ret;
+}
+
+static inline long syscall1(long n, long a1) {
+    long ret;
+    __asm__ volatile ("syscall"
+        : "=a"(ret)
+        : "a"(n), "D"(a1)
+        : "rcx", "r11", "memory");
+    return ret;
+}
+
+void forth_putchar(char c) {
+    char ch = c;
+    syscall3(1, 1, (long)&ch, 1);
+}
+
+void forth_fflush(void) {
+}
+
+int forth_getchar(void) {
+    unsigned char c;
+    long n = syscall3(0, 0, (long)&c, 1);
+    if (n <= 0) return FORTH_EOF;
+    return (int)c;
+}
+
+void forth_panic(void) {
+    syscall1(60, 1);
+    __builtin_unreachable();
+}
+
+int64_t forth_strtoll(const char* str, char** endptr, int base) {
+    const char* s = str;
+    int neg = 0;
+    int64_t val = 0;
+    while (forth_isspace(*s)) s++;
+    if (*s == '-') { neg = 1; s++; }
+    else if (*s == '+') { s++; }
+    while (*s >= '0' && *s <= '9') {
+        val = val * base + (*s - '0');
+        s++;
+    }
+    if (endptr) *endptr = (char*)s;
+    return neg ? -val : val;
+}
+
+static void print_str(const char* s) {
+    while (*s) forth_putchar(*s++);
+}
+
+static void print_int(long long v) {
+    char buf[32];
+    int i = 30;
+    int neg = 0;
+    if (v < 0) { neg = 1; v = -v; }
+    buf[31] = '\0';
+    if (v == 0) {
+        buf[i--] = '0';
+    } else {
+        while (v > 0 && i >= 0) {
+            buf[i--] = '0' + (v % 10);
+            v /= 10;
+        }
+    }
+    if (neg) buf[i--] = '-';
+    print_str(&buf[i + 1]);
+}
+
+void forth_printf(const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    while (*fmt) {
+        if (*fmt == '%' && *(fmt + 1)) {
+            fmt++;
+            if (*fmt == 's') {
+                print_str(va_arg(ap, const char*));
+            } else if (*fmt == 'c') {
+                forth_putchar((char)va_arg(ap, int));
+            } else if (*fmt == '%') {
+                forth_putchar('%');
+            } else if (*fmt == 'l') {
+                if (*(fmt + 1) == 'l' && (*(fmt + 2) == 'd' || *(fmt + 2) == 'i' || *(fmt + 2) == 'u')) {
+                    fmt += 2;
+                    print_int(va_arg(ap, long long));
+                }
+            } else if (*fmt == 'd' || *fmt == 'i' || *fmt == 'u') {
+                print_int(va_arg(ap, int));
+            } else {
+                forth_putchar('%');
+                forth_putchar(*fmt);
+            }
+        } else {
+            forth_putchar(*fmt);
+        }
+        fmt++;
+    }
+    va_end(ap);
+}
+
+void _start(void) {
+    forth_run();
+    syscall1(60, 0);
+    __builtin_unreachable();
+}

platform_hosted.c

@@ -0,0 +1,38 @@
+#include "forth.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <stdarg.h>
+
+void forth_putchar(char c) {
+    putchar((unsigned char)c);
+}
+
+int forth_getchar(void) {
+    return getchar();
+}
+
+void forth_fflush(void) {
+    fflush(stdout);
+}
+
+void forth_panic(void) {
+    for (;;);
+}
+
+int64_t forth_strtoll(const char* str, char** endptr, int base) {
+    return (int64_t)strtoll(str, endptr, base);
+}
+
+void forth_printf(const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    vprintf(fmt, ap);
+    va_end(ap);
+}
+
+int main(void) {
+    forth_run();
+    return 0;
+}