Some more Fun VM and Rust interaction. (0.38.2)

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.10)
-project(fun VERSION 0.38.1 LANGUAGES C)
+project(fun VERSION 0.38.2 LANGUAGES C)
 
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)

cmake/Targets.cmake

@@ -17,7 +17,6 @@ target_include_directories(fun_core PUBLIC
 
 # Apply options to core
 if(FUN_DEBUG)
-  message(STATUS "FUN_DEBUG enabled: building with verbose debug logging")
   target_compile_definitions(fun_core PUBLIC FUN_VERSION="${PROJECT_VERSION}")
   target_compile_definitions(fun_core PUBLIC FUN_DEBUG=1)
 endif()

docs/rust.md

@@ -1,5 +1,7 @@
 # Writing Rust-backed opcodes for Fun VM
 
+!!! CAUTION !!! I am not very experienced in using Rust. This should show that it is possible to implement opcodes in Rust and integrate them with the Fun VM.
+
 This guide explains how to implement VM opcodes in Rust, wire them into the C VM, and use them from Fun scripts.
 
 It assumes you are comfortable with basic Rust and C and have a working Fun checkout.

examples/rust_hello.fun

@@ -4,7 +4,7 @@
  * This file is part of the Fun programming language.
  * https://fun-lang.xyz/
  *
- * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
  * Licensed under the terms of the Apache-2.0 license.
  * https://opensource.org/license/apache-2-0
  *

examples/rust_hello_args.fun

@@ -4,7 +4,7 @@
  * This file is part of the Fun programming language.
  * https://fun-lang.xyz/
  *
- * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
  * Licensed under the terms of the Apache-2.0 license.
  * https://opensource.org/license/apache-2-0
  *

examples/rust_vm_access.fun

@@ -0,0 +1,39 @@
+#!/usr/bin/env fun
+
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-29
+ */
+
+/*
+ * Rust-backed VM access demo:
+ *   - rust_get_sp()   -> reads vm.sp (stack pointer) using raw pointer + offset from Rust
+ *   - rust_set_exit(N) -> writes vm.exit_code = N from Rust
+ */
+
+print("[Rust VM access demo]")
+
+/* Read vm.sp via Rust and print it */
+print("vm.sp (from Rust) = " + to_string(rust_get_sp()))
+
+/* Write vm.exit_code via Rust (not directly observable without VM inspection) */
+print("Setting vm.exit_code to 5 via Rust...")
+rust_set_exit(42)
+
+print("Now exiting...")
+
+/* Expected output:
+[Rust VM access demo]
+vm.sp (from Rust) = 0
+Setting vm.exit_code to 42 via Rust...
+Now exiting...
+*/
+
+// "echo $?" will show the exit code:
+// 42

src/bytecode.c

@@ -208,6 +208,8 @@ static const char *opcode_name(OpCode op) {
         case OP_FMAX: return "FMAX";
         case OP_RUST_HELLO: return "RUST_HELLO";
         case OP_RUST_HELLO_ARGS: return "RUST_HELLO_ARGS";
+        case OP_RUST_GET_SP: return "RUST_GET_SP";
+        case OP_RUST_SET_EXIT: return "RUST_SET_EXIT";
         default: return "???";
     }
 }

src/bytecode.h

@@ -266,6 +266,8 @@ typedef enum {
     // Rust FFI demo opcode(s)
     OP_RUST_HELLO,        // pushes string returned from Rust (hello world)
     OP_RUST_HELLO_ARGS,   // pops message string; prints it via Rust; pushes Nil
+    OP_RUST_GET_SP,       // pushes current VM stack pointer (via Rust reading VM memory)
+    OP_RUST_SET_EXIT,     // pops int and sets VM exit_code (via Rust writing VM memory)
 
     /* Notcurses TUI (optional) */
     OP_NC_INIT,           // initializes Notcurses; returns 1 on success, 0 on failure

src/parser.c

@@ -801,6 +801,21 @@ static int emit_primary(Bytecode *bc, const char *src, size_t len, size_t *pos)
                 free(name);
                 return 1;
             }
+            if (strcmp(name, "rust_get_sp") == 0) {
+                (*pos)++; /* '(' */
+                if (!consume_char(src, len, pos, ')')) { parser_fail(*pos, "rust_get_sp expects ()"); free(name); return 0; }
+                bytecode_add_instruction(bc, OP_RUST_GET_SP, 0);
+                free(name);
+                return 1;
+            }
+            if (strcmp(name, "rust_set_exit") == 0) {
+                (*pos)++; /* '(' */
+                if (!emit_expression(bc, src, len, pos)) { parser_fail(*pos, "rust_set_exit expects (code:int)"); free(name); return 0; }
+                if (!consume_char(src, len, pos, ')')) { parser_fail(*pos, "Expected ')' after rust_set_exit arg"); free(name); return 0; }
+                bytecode_add_instruction(bc, OP_RUST_SET_EXIT, 0);
+                free(name);
+                return 1;
+            }
             if (strcmp(name, "os_list_dir") == 0) {
                 (*pos)++; /* '(' */
                 if (!emit_expression(bc, src, len, pos)) { parser_fail(*pos, "os_list_dir expects (path)"); free(name); return 0; }

src/rust/src/lib.rs

@@ -2,15 +2,13 @@
  * This file is part of the Fun programming language.
  * https://fun-lang.xyz/
  *
- * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
  * Licensed under the terms of the Apache-2.0 license.
  * https://opensource.org/license/apache-2-0
  *
  * Added: 2026-01-27
  */
 
-#![no_std]
-
 // Use an FFI-safe opaque handle for the VM pointer
 pub type Vm = core::ffi::c_void;
 
@@ -37,7 +35,7 @@ pub extern "C" fn fun_rust_get_string() -> *const core::ffi::c_char {
     b"Hello from Rust ops!\0".as_ptr() as *const _
 }
 
-// Print a C string via libc printf to stdout (acceptable under no_std via extern)
+// Print a C string via libc printf to stdout
 #[no_mangle]
 pub extern "C" fn fun_rust_print_string(msg: *const core::ffi::c_char) -> i32 {
     unsafe {
@@ -50,12 +48,4 @@ pub extern "C" fn fun_rust_print_string(msg: *const core::ffi::c_char) -> i32 {
     0
 }
 
-// Provide personality symbol to satisfy some linkers in no_std builds
-#[no_mangle]
-pub extern "C" fn rust_eh_personality() {}
-
-// Minimal panic handler for no_std; abort behavior requested via Cargo profile
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}
+// No custom panic handler; use std default

src/rust/src/vm/mod.rs

@@ -2,7 +2,7 @@
  * This file is part of the Fun programming language.
  * https://fun-lang.xyz/
  *
- * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
  * Licensed under the terms of the Apache-2.0 license.
  * https://opensource.org/license/apache-2-0
  *
@@ -16,10 +16,18 @@
 //! ABI helpers declared on the C side (`vm_pop_i64`, `vm_push_i64`).
 
 use super::Vm;
+//use core::mem::size_of;
+use core::ptr;
 
 extern "C" {
     fn vm_pop_i64(vm: *mut Vm) -> i64;
     fn vm_push_i64(vm: *mut Vm, v: i64);
+    fn vm_as_mut_ptr(vm: *mut Vm) -> *mut core::ffi::c_void;
+    fn vm_sizeof() -> usize;
+    fn vm_value_sizeof() -> usize;
+    fn vm_offset_of_exit_code() -> usize;
+    fn vm_offset_of_sp() -> usize;
+    fn vm_offset_of_stack() -> usize;
 }
 
 /// Multiply the top two integers on the VM stack.
@@ -68,3 +76,29 @@ pub extern "C" fn fun_op_rdiv(vm: *mut Vm) -> i32 {
     }
     0
 }
+
+/// Demo: push current stack pointer (vm.sp) using raw offset access.
+#[no_mangle]
+pub extern "C" fn fun_op_rget_sp(vm: *mut Vm) -> i32 {
+    unsafe {
+        let base = vm_as_mut_ptr(vm) as *mut u8;
+        let off_sp = vm_offset_of_sp();
+        let sp_ptr = base.add(off_sp) as *const i32;
+        let sp = ptr::read(sp_ptr);
+        vm_push_i64(vm, sp as i64);
+    }
+    0
+}
+
+/// Demo: set vm.exit_code to a value popped from the stack (i64 -> i32 cast).
+#[no_mangle]
+pub extern "C" fn fun_op_rset_exit(vm: *mut Vm) -> i32 {
+    unsafe {
+        let code = vm_pop_i64(vm) as i32;
+        let base = vm_as_mut_ptr(vm) as *mut u8;
+        let off_ec = vm_offset_of_exit_code();
+        let ec_ptr = base.add(off_ec) as *mut i32;
+        ptr::write(ec_ptr, code);
+    }
+    0
+}

src/vm.c

@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
+#include <stddef.h>
 #include <time.h>
 #include <math.h>
 
@@ -488,6 +489,35 @@ void vm_push_i64(VM *vm, int64_t v) {
     push_value(vm, make_int(v));
 }
 
+/* --- Extended C ABI for Rust to access VM internals (unsafe) --- */
+size_t vm_sizeof(void) {
+    return sizeof(VM);
+}
+
+size_t vm_value_sizeof(void) {
+    return sizeof(Value);
+}
+
+void *vm_as_mut_ptr(VM *vm) {
+    return (void*)vm;
+}
+
+size_t vm_offset_of_exit_code(void) {
+    return offsetof(VM, exit_code);
+}
+
+size_t vm_offset_of_sp(void) {
+    return offsetof(VM, sp);
+}
+
+size_t vm_offset_of_stack(void) {
+    return offsetof(VM, stack);
+}
+
+size_t vm_offset_of_globals(void) {
+    return offsetof(VM, globals);
+}
+
 static void frame_init(Frame *f) {
     f->fn = NULL;
     f->ip = 0;
@@ -758,6 +788,9 @@ void vm_run(VM *vm, Bytecode *entry) {
 
             /* Rust FFI demo opcode(s) */
             #include "vm/rust/hello.c"
+            #include "vm/rust/hello_args.c"
+            #include "vm/rust/get_sp.c"
+            #include "vm/rust/set_exit.c"
 
             #include "vm/os/env.c"
             #include "vm/os/env_all.c"

src/vm.h

@@ -11,6 +11,7 @@
 #define FUN_VM_H
 
 #include "bytecode.h"
+#include <stddef.h>
 
 #define MAX_FRAMES 128
 #define MAX_FRAME_LOCALS 64
@@ -56,7 +57,7 @@ static const char *opcode_names[] = {
     "TRY_PUSH","TRY_POP","THROW",
     "FMIN","FMAX",
     /* Rust FFI demo */
-    "RUST_HELLO","RUST_HELLO_ARGS",
+    "RUST_HELLO","RUST_HELLO_ARGS","RUST_GET_SP","RUST_SET_EXIT",
     /* Notcurses TUI (optional) */
     "NC_INIT","NC_SHUTDOWN","NC_CLEAR","NC_DRAW_TEXT","NC_GETCH"
 };
@@ -160,4 +161,23 @@ const char *fun_rust_get_string(void);
 /* Rust function that prints a passed C string, returns 0 on success. */
 int fun_rust_print_string(const char *msg);
 
+/* --- Extended C ABI for Rust to access VM internals (unsafe) --- */
+/* Size helpers for Rust side to compute offsets and do pointer math */
+size_t vm_sizeof(void);
+size_t vm_value_sizeof(void);
+
+/* Get a mutable byte pointer to the VM object. Extremely unsafe; intended for
+ * low-level FFI where Rust wants parity access with C code. */
+void *vm_as_mut_ptr(VM *vm);
+
+/* Offsets of commonly accessed VM fields to avoid re-declaring the struct layout in Rust */
+size_t vm_offset_of_exit_code(void);
+size_t vm_offset_of_sp(void);
+size_t vm_offset_of_stack(void);
+size_t vm_offset_of_globals(void);
+
+/* Demo Rust ops using the extended ABI */
+int fun_op_rget_sp(VM *vm);
+int fun_op_rset_exit(VM *vm);
+
 #endif

src/vm/rust/get_sp.c

@@ -0,0 +1,26 @@
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-29
+ */
+
+/*
+ * Rust FFI demo opcode: OP_RUST_GET_SP
+ * Calls into Rust to read vm.sp via raw pointer math and pushes it (int).
+ */
+case OP_RUST_GET_SP: {
+#ifdef FUN_WITH_RUST
+    extern int fun_op_rget_sp(VM *vm);
+    int rc = fun_op_rget_sp(vm);
+    (void)rc; /* rc currently unused; 0 means OK */
+#else
+    vm_raise_error(vm, "RUST_GET_SP requires FUN_WITH_RUST=ON at build time");
+    push_value(vm, make_int(-1));
+#endif
+    break;
+}

src/vm/rust/hello.c

@@ -2,7 +2,7 @@
  * This file is part of the Fun programming language.
  * https://fun-lang.xyz/
  *
- * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
  * Licensed under the terms of the Apache-2.0 license.
  * https://opensource.org/license/apache-2-0
  *
@@ -25,29 +25,3 @@ case OP_RUST_HELLO: {
 #endif
     break;
 }
-
-/*
- * Rust FFI demo opcode with argument: OP_RUST_HELLO_ARGS
- * Pops a string from the stack and asks Rust to print it. Pushes Nil.
- */
-case OP_RUST_HELLO_ARGS: {
-#ifdef FUN_WITH_RUST
-    Value vmsg = pop_value(vm);
-    char *msg = value_to_string_alloc(&vmsg);
-    free_value(vmsg);
-    if (msg) {
-        fun_rust_print_string(msg);
-        free(msg);
-    } else {
-        fun_rust_print_string("");
-    }
-    push_value(vm, make_nil());
-#else
-    /* Still pop and free the arg to keep stack sane */
-    Value vmsg = pop_value(vm);
-    free_value(vmsg);
-    vm_raise_error(vm, "RUST_HELLO_ARGS requires FUN_WITH_RUST=ON at build time");
-    push_value(vm, make_nil());
-#endif
-    break;
-}

src/vm/rust/hello_args.c

@@ -0,0 +1,36 @@
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-29
+ */
+
+/*
+ * Rust FFI demo opcode with argument: OP_RUST_HELLO_ARGS
+ * Pops a string from the stack and asks Rust to print it. Pushes Nil.
+ */
+case OP_RUST_HELLO_ARGS: {
+#ifdef FUN_WITH_RUST
+    Value vmsg = pop_value(vm);
+    char *msg = value_to_string_alloc(&vmsg);
+    free_value(vmsg);
+    if (msg) {
+        fun_rust_print_string(msg);
+        free(msg);
+    } else {
+        fun_rust_print_string("");
+    }
+    push_value(vm, make_nil());
+#else
+    /* Still pop and free the arg to keep stack sane */
+    Value vmsg = pop_value(vm);
+    free_value(vmsg);
+    vm_raise_error(vm, "RUST_HELLO_ARGS requires FUN_WITH_RUST=ON at build time");
+    push_value(vm, make_nil());
+#endif
+    break;
+}

src/vm/rust/set_exit.c

@@ -0,0 +1,33 @@
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2026 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-29
+ */
+
+/*
+ * Rust FFI demo opcode: OP_RUST_SET_EXIT
+ * Pops an int code and asks Rust to write it into vm.exit_code.
+ */
+case OP_RUST_SET_EXIT: {
+#ifdef FUN_WITH_RUST
+    extern int fun_op_rset_exit(VM *vm);
+    /* Expect an integer on the stack already (produced by prior ops) */
+    /* fun_op_rset_exit will pop it and store into vm.exit_code */
+    int rc = fun_op_rset_exit(vm);
+    (void)rc;
+    /* push Nil as a conventional result */
+    push_value(vm, make_nil());
+#else
+    /* pop and ignore to keep stack sane */
+    Value v = pop_value(vm);
+    free_value(v);
+    vm_raise_error(vm, "RUST_SET_EXIT requires FUN_WITH_RUST=ON at build time");
+    push_value(vm, make_nil());
+#endif
+    break;
+}