What is CPP? Holy shit... (0.38.4)

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.10)
-project(fun VERSION 0.38.3 LANGUAGES C)
+project(fun VERSION 0.38.4 LANGUAGES C)
 
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
@@ -19,14 +19,21 @@ else()
   set(_FUN_DEBUG_STATE "DISABLED")
 endif()
 
-if(FUN_WITH_RUST)
-  set(_FUN_WITH_RUST_STATE "ENABLED")
+if(FUN_WITH_CPP)
+    set(_FUN_WITH_CPP_STATE "ENABLED")
 else()
-  set(_FUN_WITH_RUST_STATE "DISABLED")
+    set(_FUN_WITH_CPP_STATE "DISABLED")
+endif()
+
+if(FUN_WITH_RUST)
+    set(_FUN_WITH_RUST_STATE "ENABLED")
+else()
+    set(_FUN_WITH_RUST_STATE "DISABLED")
 endif()
 
 message(STATUS "==== Fun build options ====")
 message(STATUS "  FUN_DEBUG: ${_FUN_DEBUG_STATE}")
+message(STATUS "  FUN_WITH_CPP: ${_FUN_WITH_CPP_STATE}")
 message(STATUS "  FUN_WITH_RUST: ${_FUN_WITH_RUST_STATE}")
 message(STATUS "===========================")
 
@@ -98,6 +105,36 @@ if(FUN_WITH_RUST)
   endif()
 endif()
 
+# --- Optional C++ opcode demo ---
+option(FUN_WITH_CPP "Build and link C++ opcode demo" OFF)
+if(FUN_WITH_CPP)
+  enable_language(CXX)
+
+  add_library(fun_cpp_ops STATIC
+    src/vm/cpp/add.cpp
+  )
+
+  # Compile definitions propagate to C targets that dispatch the opcode
+  target_compile_definitions(fun_cpp_ops PUBLIC FUN_WITH_CPP)
+  target_include_directories(fun_cpp_ops PUBLIC ${CMAKE_SOURCE_DIR}/src)
+
+  # Link the C++ ops into the core so executables can call them
+  if(TARGET fun_core)
+    target_link_libraries(fun_core PRIVATE fun_cpp_ops)
+    target_compile_definitions(fun_core PRIVATE FUN_WITH_CPP)
+  endif()
+
+  # Also propagate to test targets (if they might use it)
+  if(TARGET test_opcodes)
+    target_link_libraries(test_opcodes PRIVATE fun_cpp_ops)
+    target_compile_definitions(test_opcodes PRIVATE FUN_WITH_CPP)
+  endif()
+
+  if(TARGET fun)
+    target_compile_definitions(fun PRIVATE FUN_WITH_CPP)
+  endif()
+endif()
+
 # --- Size optimization for final binaries (Release) ---
 # Enable function/data sectioning for better GC; safe for all configs.
 add_compile_options(-ffunction-sections -fdata-sections)

examples/cpp_add.fun

@@ -0,0 +1,28 @@
+#!/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
+ */
+
+/*
+Build:
+  cmake -S . -B build_debug -DFUN_WITH_CPP=ON
+  cmake --build build_debug --target fun
+Run:
+  build_debug/fun examples/cpp_add.fun
+*/
+
+number x = cpp_add(2, 40)
+//print("typeof(x): " + typeof(x))
+print(x)
+
+/* Expected output:
+42
+*/

examples/rust_vm_access.fun

@@ -23,7 +23,7 @@ print("[Rust VM access demo]")
 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...")
+print("Setting vm.exit_code to 42 via Rust...")
 rust_set_exit(42)
 
 print("Now exiting...")

make

@@ -31,6 +31,7 @@ if [ "$target" = "all" ]; then
       -DFUN_WITH_TCLTK=ON \
       -DFUN_WITH_INI=ON \
       -DFUN_WITH_NOTCURSES=ON \
+      -DFUN_WITH_CPP=ON \
     && cmake --build build --target fun
 elif [ "$target" = "all_debug" ]; then
   rm -rf build \
@@ -46,6 +47,7 @@ elif [ "$target" = "all_debug" ]; then
       -DFUN_WITH_TCLTK=ON \
       -DFUN_WITH_INI=ON \
       -DFUN_WITH_NOTCURSES=ON \
+      -DFUN_WITH_CPP=ON \
       -DFUN_DEBUG=ON \
     && cmake --build build --target fun
 elif [ "$target" = "alpine" ]; then
@@ -59,7 +61,29 @@ elif [ "$target" = "alpine" ]; then
       -DFUN_WITH_XML2=ON \
       -DFUN_WITH_JSON=ON \
       -DFUN_WITH_INI=ON \
+      -DFUN_WITH_CPP=ON \
     && cmake --build build --target fun
+elif [ "$target" = "cpp_all" ]; then
+  rm -rf build \
+    && cmake -S . -B build \
+      -DFUN_WITH_PCSC=ON \
+      -DFUN_WITH_REPL=ON \
+      -DFUN_WITH_LIBSQL=ON \
+      -DFUN_WITH_SQLITE=ON \
+      -DFUN_WITH_CURL=ON \
+      -DFUN_WITH_PCRE2=ON \
+      -DFUN_WITH_XML2=ON \
+      -DFUN_WITH_JSON=ON \
+      -DFUN_WITH_TCLTK=ON \
+      -DFUN_WITH_INI=ON \
+      -DFUN_WITH_NOTCURSES=ON \
+      -DFUN_WITH_CPP=ON \
+    && cmake --build build --target fun
+  elif [ "$target" = "cpp_minimal" ]; then
+    rm -rf build \
+      && cmake -S . -B build \
+        -DFUN_WITH_CPP=ON \
+      && cmake --build build --target fun
 elif [ "$target" = "debug" ]; then
   rm -rf build \
     && cmake -S . -B build \
@@ -102,6 +126,7 @@ elif [ "$target" = "rust_all" ]; then
       -DFUN_WITH_TCLTK=ON \
       -DFUN_WITH_INI=ON \
       -DFUN_WITH_RUST=ON \
+      -DFUN_WITH_CPP=ON \
       -DFUN_DEBUG=OFF \
     && cmake --build build --target fun
 elif [ "$target" = "rust_minimal" ]; then
@@ -115,6 +140,8 @@ else
   echo " - all";
   echo " - all_debug";
   echo " - alpine";
+  echo " - cpp_all";
+  echo " - cpp_minimal";
   echo " - debug";
   echo " - freebsd";
   echo " - install";

src/bytecode.h

@@ -270,6 +270,9 @@ typedef enum {
     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)
 
+    // C++ demo opcode(s)
+    OP_CPP_ADD,           // pops b, a; pushes (a + b)
+
     /* Notcurses TUI (optional) */
     OP_NC_INIT,           // initializes Notcurses; returns 1 on success, 0 on failure
     OP_NC_SHUTDOWN,       // shuts down Notcurses; returns 0

src/parser.c

@@ -824,6 +824,16 @@ static int emit_primary(Bytecode *bc, const char *src, size_t len, size_t *pos)
                 free(name);
                 return 1;
             }
+            if (strcmp(name, "cpp_add") == 0) {
+                (*pos)++; /* '(' */
+                if (!emit_expression(bc, src, len, pos)) { parser_fail(*pos, "cpp_add expects (a:int, b:int)"); free(name); return 0; }
+                if (!consume_char(src, len, pos, ',')) { parser_fail(*pos, "cpp_add expects two arguments"); free(name); return 0; }
+                if (!emit_expression(bc, src, len, pos)) { parser_fail(*pos, "cpp_add expects (a:int, b:int)"); free(name); return 0; }
+                if (!consume_char(src, len, pos, ')')) { parser_fail(*pos, "Expected ')' after cpp_add args"); free(name); return 0; }
+                bytecode_add_instruction(bc, OP_CPP_ADD, 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/vm.c

@@ -897,6 +897,22 @@ void vm_run(VM *vm, Bytecode *entry) {
             #include "vm/sqlite/query.c"
             #endif
 
+            /* C++ demo opcodes (guarded) */
+            #if defined(FUN_WITH_CPP)
+            case OP_CPP_ADD: {
+                int rc = fun_op_cpp_add(vm);
+                if (rc != 0) {
+                    vm_raise_error(vm, "cpp_add failed");
+                }
+                break;
+            }
+            #else
+            case OP_CPP_ADD: {
+                vm_raise_error(vm, "CPP support is not enabled (build with -DFUN_WITH_CPP=ON)");
+                break;
+            }
+            #endif
+
             /* libsql ops (independent) */
             #ifdef FUN_WITH_LIBSQL
             #include "vm/libsql/open.c"

src/vm.h

@@ -58,6 +58,8 @@ static const char *opcode_names[] = {
     "FMIN","FMAX",
     /* Rust FFI demo */
     "RUST_HELLO","RUST_HELLO_ARGS","RUST_HELLO_ARGS_RETURN","RUST_GET_SP","RUST_SET_EXIT",
+    /* C++ demo */
+    "CPP_ADD",
     /* Notcurses TUI (optional) */
     "NC_INIT","NC_SHUTDOWN","NC_CLEAR","NC_DRAW_TEXT","NC_GETCH"
 };
@@ -165,6 +167,9 @@ char *fun_rust_echo_string(const char *input);
 /* Free a C string previously returned by fun_rust_echo_string. */
 void fun_rust_string_free(char *ptr);
 
+/* C++ demo opcode entry point (C ABI) */
+int fun_op_cpp_add(struct VM *vm);
+
 /* --- 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);

src/vm/cpp/add.cpp

@@ -0,0 +1,28 @@
+/*
+* 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
+ */
+
+/*
+ * Minimal C++ opcode for Fun VM — cpp_add
+ * Build is gated by -DFUN_WITH_CPP=ON (see CMake).
+ */
+
+#include <cstdint>
+
+extern "C" {
+#include "vm.h" // C header; provides VM, vm_pop_i64, vm_push_i64
+}
+
+extern "C" int fun_op_cpp_add(VM *vm) {
+    int64_t b = vm_pop_i64(vm);
+    int64_t a = vm_pop_i64(vm);
+    vm_push_i64(vm, a + b);
+    return 0; // success
+}