Address review: fix merge conflicts with develop

Requested by @lefticus in PR #657 review.

.github/workflows/emscripten.yml

@@ -0,0 +1,71 @@
+name: Emscripten
+
+on:
+  push:
+    branches: [develop, main]
+  pull_request:
+    branches: [develop, main]
+  workflow_dispatch:
+
+jobs:
+  emscripten:
+    name: Emscripten WebAssembly Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Emscripten
+        uses: mymindstorm/setup-emsdk@v14
+
+      - name: Configure
+        run: emcmake cmake -B build-em -S emscripten -DCMAKE_BUILD_TYPE=Release
+
+      - name: Build
+        run: cmake --build build-em -j
+
+      - name: Verify artifacts
+        run: |
+          test -f build-em/chaiscript.js
+          test -f build-em/chaiscript.wasm
+          test -f build-em/chaiscript.html
+          echo "All expected artifacts present"
+          ls -lh build-em/chaiscript.*
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: chaiscript-web
+          path: |
+            build-em/chaiscript.js
+            build-em/chaiscript.wasm
+            build-em/chaiscript.html
+          retention-days: 90
+
+  publish:
+    name: Publish WASM Release
+    needs: emscripten
+    if: github.ref == 'refs/heads/develop' && github.event_name == 'push'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: chaiscript-web
+          path: artifacts
+
+      - name: Publish to wasm-latest release
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Flatten: artifacts may contain build-em/ subdirectory
+          find artifacts -type f \( -name 'chaiscript.js' -o -name 'chaiscript.wasm' -o -name 'chaiscript.html' \) -exec cp {} . \;
+
+          # Delete existing release if present, then recreate
+          gh release delete wasm-latest --repo "$GITHUB_REPOSITORY" -y 2>/dev/null || true
+          gh release create wasm-latest \
+            --repo "$GITHUB_REPOSITORY" \
+            --title "ChaiScript WASM Build (latest)" \
+            --notes "Auto-published from develop branch. Built with Emscripten for browser use." \
+            --prerelease \
+            chaiscript.js chaiscript.wasm chaiscript.html

CMakeLists.txt

@@ -413,6 +413,9 @@ if(BUILD_TESTING)
         "CHAI_USE_PATH=${CMAKE_CURRENT_SOURCE_DIR}/unittests/"
         "CHAI_MODULE_PATH=${CMAKE_CURRENT_BINARY_DIR}/"
       )
+      add_executable(async_engine_lifetime_test unittests/async_engine_lifetime_test.cpp)
+      target_link_libraries(async_engine_lifetime_test ${LIBS})
+      add_test(NAME Async_Engine_Lifetime_Test COMMAND async_engine_lifetime_test)
     endif()
 
     add_executable(multifile_test
@@ -423,6 +426,10 @@ if(BUILD_TESTING)
     target_link_libraries(multifile_test ${LIBS})
     add_test(NAME MultiFile_Test COMMAND multifile_test)
 
+    add_executable(emscripten_eval_test unittests/emscripten_eval_test.cpp)
+    target_link_libraries(emscripten_eval_test ${LIBS})
+    add_test(NAME Emscripten_Eval_Test COMMAND emscripten_eval_test)
+
     install(TARGETS test_module RUNTIME DESTINATION bin LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}/chaiscript")
   endif()
 endif()

emscripten/CMakeLists.txt

@@ -0,0 +1,35 @@
+# Emscripten/WebAssembly build for ChaiScript
+# Based on work by Rob Loach: https://github.com/RobLoach/ChaiScript.js
+#
+# Usage:
+#   emcmake cmake -B build-em -S emscripten
+#   cmake --build build-em
+
+cmake_minimum_required(VERSION 3.12)
+project(chaiscript_em)
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Emscripten-specific compiler/linker flags
+add_definitions(-DCHAISCRIPT_NO_THREADS -DCHAISCRIPT_NO_DYNLOAD)
+
+add_executable(chaiscript chaiscript_em.cpp)
+target_include_directories(chaiscript PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/../include)
+
+# Emscripten link flags: enable embind, allow memory growth, export as ES module-compatible
+target_link_options(chaiscript PRIVATE
+  --bind
+  -sALLOW_MEMORY_GROWTH=1
+  -sEXPORT_ES6=0
+  -sMODULARIZE=0
+  -sINVOKE_RUN=0
+)
+
+# Copy the HTML shell to the build output directory
+add_custom_command(TARGET chaiscript POST_BUILD
+  COMMAND ${CMAKE_COMMAND} -E copy
+    ${CMAKE_CURRENT_SOURCE_DIR}/chaiscript.html
+    ${CMAKE_CURRENT_BINARY_DIR}/chaiscript.html
+  COMMENT "Copying HTML frontend to build directory"
+)

emscripten/chaiscript.html

@@ -0,0 +1,237 @@
+<!doctype html>
+<!--
+  ChaiScript Emscripten Frontend
+  Based on work by Rob Loach: https://github.com/RobLoach/ChaiScript.js
+  Copyright 2019, Rob Loach
+  Copyright 2009-2018, Jason Turner
+  Licensed under the BSD License. See "license.txt" for details.
+-->
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>ChaiScript</title>
+  <style>
+    * { box-sizing: border-box; margin: 0; padding: 0; }
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
+      background: #1a1a2e;
+      color: #e0e0e0;
+      min-height: 100vh;
+      display: flex;
+      flex-direction: column;
+    }
+    header {
+      background: #16213e;
+      padding: 1rem 2rem;
+      border-bottom: 2px solid #0f3460;
+      display: flex;
+      align-items: center;
+      gap: 1rem;
+    }
+    header h1 {
+      font-size: 1.5rem;
+      color: #e94560;
+      font-weight: 700;
+    }
+    header span {
+      font-size: 0.85rem;
+      color: #888;
+    }
+    #status {
+      margin-left: auto;
+      font-size: 0.85rem;
+      padding: 0.3rem 0.8rem;
+      border-radius: 4px;
+      background: #0f3460;
+    }
+    #status.ready { color: #4ecca3; }
+    #status.loading { color: #e9c46a; }
+    #status.error { color: #e94560; }
+    main {
+      flex: 1;
+      display: flex;
+      gap: 0;
+    }
+    .panel {
+      flex: 1;
+      display: flex;
+      flex-direction: column;
+      min-width: 0;
+    }
+    .panel-header {
+      background: #16213e;
+      padding: 0.5rem 1rem;
+      font-size: 0.8rem;
+      text-transform: uppercase;
+      letter-spacing: 0.1em;
+      color: #888;
+      border-bottom: 1px solid #0f3460;
+    }
+    #input {
+      flex: 1;
+      background: #0d1117;
+      color: #c9d1d9;
+      border: none;
+      padding: 1rem;
+      font-family: "SF Mono", "Fira Code", "Fira Mono", Menlo, Consolas, monospace;
+      font-size: 0.9rem;
+      line-height: 1.6;
+      resize: none;
+      outline: none;
+      tab-size: 2;
+    }
+    .divider {
+      width: 2px;
+      background: #0f3460;
+    }
+    #output {
+      flex: 1;
+      background: #0d1117;
+      padding: 1rem;
+      font-family: "SF Mono", "Fira Code", "Fira Mono", Menlo, Consolas, monospace;
+      font-size: 0.9rem;
+      line-height: 1.6;
+      overflow-y: auto;
+      white-space: pre-wrap;
+      word-break: break-all;
+    }
+    .output-line { color: #c9d1d9; }
+    .output-error { color: #e94560; }
+    footer {
+      background: #16213e;
+      padding: 0.5rem 1rem;
+      display: flex;
+      gap: 0.5rem;
+      align-items: center;
+      border-top: 2px solid #0f3460;
+    }
+    button {
+      background: #e94560;
+      color: #fff;
+      border: none;
+      padding: 0.4rem 1.2rem;
+      border-radius: 4px;
+      cursor: pointer;
+      font-size: 0.85rem;
+      font-weight: 600;
+    }
+    button:hover { background: #c73652; }
+    button:disabled { background: #555; cursor: not-allowed; }
+    #btn-clear {
+      background: #0f3460;
+    }
+    #btn-clear:hover { background: #1a4a8a; }
+    .hint {
+      margin-left: auto;
+      font-size: 0.75rem;
+      color: #555;
+    }
+  </style>
+</head>
+<body>
+  <header>
+    <h1>ChaiScript</h1>
+    <span>Interactive Playground</span>
+    <div id="status" class="loading">Loading...</div>
+  </header>
+  <main>
+    <div class="panel">
+      <div class="panel-header">Input</div>
+      <textarea id="input" spellcheck="false">// Welcome to ChaiScript!
+// Write your code here and click Run (or press Ctrl+Enter).
+
+def greet(name) {
+  return "Hello, " + name + "!"
+}
+
+print(greet("World"))
+print(greet("ChaiScript"))
+
+// Math example
+def factorial(n) {
+  if (n <= 1) { return 1 }
+  return n * factorial(n - 1)
+}
+
+print("5! = " + to_string(factorial(5)))
+print("10! = " + to_string(factorial(10)))
+</textarea>
+    </div>
+    <div class="divider"></div>
+    <div class="panel">
+      <div class="panel-header">Output</div>
+      <div id="output"></div>
+    </div>
+  </main>
+  <footer>
+    <button id="btn-run" disabled>Run</button>
+    <button id="btn-clear">Clear</button>
+    <span class="hint">Ctrl+Enter to run</span>
+  </footer>
+
+  <script>
+    var outputEl = document.getElementById('output');
+    var inputEl = document.getElementById('input');
+    var btnRun = document.getElementById('btn-run');
+    var btnClear = document.getElementById('btn-clear');
+    var statusEl = document.getElementById('status');
+
+    function appendOutput(text, className) {
+      var line = document.createElement('div');
+      line.className = className || 'output-line';
+      line.textContent = text;
+      outputEl.appendChild(line);
+      outputEl.scrollTop = outputEl.scrollHeight;
+    }
+
+    var Module = {
+      print: function(text) {
+        appendOutput(text);
+      },
+      printErr: function(text) {
+        appendOutput(text, 'output-error');
+      },
+      onRuntimeInitialized: function() {
+        statusEl.textContent = 'Ready';
+        statusEl.className = 'ready';
+        btnRun.disabled = false;
+      }
+    };
+
+    function runCode() {
+      var code = inputEl.value;
+      if (!code.trim()) return;
+
+      appendOutput('> Running...', 'output-line');
+      try {
+        Module.eval(code);
+      } catch (e) {
+        appendOutput('Error: ' + e.message, 'output-error');
+      }
+      appendOutput('', 'output-line');
+    }
+
+    btnRun.addEventListener('click', runCode);
+    btnClear.addEventListener('click', function() {
+      outputEl.innerHTML = '';
+    });
+
+    inputEl.addEventListener('keydown', function(e) {
+      if (e.ctrlKey && e.key === 'Enter') {
+        e.preventDefault();
+        runCode();
+      }
+      // Tab key inserts spaces
+      if (e.key === 'Tab') {
+        e.preventDefault();
+        var start = this.selectionStart;
+        var end = this.selectionEnd;
+        this.value = this.value.substring(0, start) + '  ' + this.value.substring(end);
+        this.selectionStart = this.selectionEnd = start + 2;
+      }
+    });
+  </script>
+  <script src="chaiscript.js"></script>
+</body>
+</html>

emscripten/chaiscript_em.cpp

@@ -0,0 +1,23 @@
+// This file is distributed under the BSD License.
+// See "license.txt" for details.
+// Copyright 2019, Rob Loach (https://github.com/RobLoach/ChaiScript.js)
+// Copyright 2009-2018, Jason Turner (jason@emptycrate.com)
+// http://www.chaiscript.com
+//
+// Emscripten/WebAssembly wrapper for ChaiScript.
+// Based on work by Rob Loach: https://github.com/RobLoach/ChaiScript.js
+
+#include "chaiscript_eval.hpp"
+
+#ifdef __EMSCRIPTEN__
+#include <emscripten/bind.h>
+
+EMSCRIPTEN_BINDINGS(chaiscript) {
+  emscripten::function("eval", &chaiscript_eval);
+  emscripten::function("evalString", &chaiscript_eval_string);
+  emscripten::function("evalBool", &chaiscript_eval_bool);
+  emscripten::function("evalInt", &chaiscript_eval_int);
+  emscripten::function("evalFloat", &chaiscript_eval_float);
+  emscripten::function("evalDouble", &chaiscript_eval_double);
+}
+#endif

emscripten/chaiscript_eval.hpp

@@ -0,0 +1,48 @@
+// This file is distributed under the BSD License.
+// See "license.txt" for details.
+// Copyright 2019, Rob Loach (https://github.com/RobLoach/ChaiScript.js)
+// Copyright 2009-2018, Jason Turner (jason@emptycrate.com)
+// http://www.chaiscript.com
+
+// Shared eval helper functions for the ChaiScript Emscripten wrapper.
+// These functions provide typed evaluation of ChaiScript expressions,
+// used by both the Emscripten/WebAssembly build and native tests.
+
+#ifndef CHAISCRIPT_EMSCRIPTEN_EVAL_HPP_
+#define CHAISCRIPT_EMSCRIPTEN_EVAL_HPP_
+
+#include <string>
+#include <chaiscript/chaiscript.hpp>
+
+namespace detail {
+inline chaiscript::ChaiScript &get_chai_instance() {
+  static chaiscript::ChaiScript chai;
+  return chai;
+}
+} // namespace detail
+
+inline void chaiscript_eval(const std::string &input) {
+  detail::get_chai_instance().eval(input);
+}
+
+inline std::string chaiscript_eval_string(const std::string &input) {
+  return detail::get_chai_instance().eval<std::string>(input);
+}
+
+inline bool chaiscript_eval_bool(const std::string &input) {
+  return detail::get_chai_instance().eval<bool>(input);
+}
+
+inline int chaiscript_eval_int(const std::string &input) {
+  return detail::get_chai_instance().eval<int>(input);
+}
+
+inline float chaiscript_eval_float(const std::string &input) {
+  return detail::get_chai_instance().eval<float>(input);
+}
+
+inline double chaiscript_eval_double(const std::string &input) {
+  return detail::get_chai_instance().eval<double>(input);
+}
+
+#endif /* CHAISCRIPT_EMSCRIPTEN_EVAL_HPP_ */

include/chaiscript/chaiscript_stdlib.hpp

@@ -49,9 +49,8 @@ namespace chaiscript {
 
 #ifndef CHAISCRIPT_NO_THREADS
       bootstrap::standard_library::future_type<std::future<chaiscript::Boxed_Value>>("future", *lib);
-      lib->add(chaiscript::fun(
-                   [](const std::function<chaiscript::Boxed_Value()> &t_func) { return std::async(std::launch::async, t_func); }),
-               "async");
+      // Note: async() is registered in ChaiScript_Basic::build_eval_system()
+      // with thread tracking to prevent heap-use-after-free on engine destruction.
 #endif
 
       json_wrap::library(*lib);

include/chaiscript/dispatchkit/bootstrap.hpp

@@ -115,6 +115,8 @@ namespace chaiscript::bootstrap {
 
     m.add(fun(&parse_string<T>), "to_" + name);
     m.add(fun([](const T t) { return t; }), "to_" + name);
+    m.add(fun([](const Boxed_Number &bn) { return bn.get_as<T>(); }), "to_" + name);
+    m.add(fun(&parse_string<T>), name);
   }
 
   /// "clone" function for a shared_ptr type. This is used in the case

include/chaiscript/dispatchkit/dispatchkit.hpp

@@ -19,6 +19,7 @@
 #include <stdexcept>
 #include <string>
 #include <string_view>
+#include <thread>
 #include <typeinfo>
 #include <utility>
 #include <vector>
@@ -370,6 +371,28 @@ namespace chaiscript {
           , m_parser(parser) {
       }
 
+      ~Dispatch_Engine() {
+        join_async_threads();
+      }
+
+      Dispatch_Engine(const Dispatch_Engine &) = delete;
+      Dispatch_Engine &operator=(const Dispatch_Engine &) = delete;
+      Dispatch_Engine(Dispatch_Engine &&) = default;
+      Dispatch_Engine &operator=(Dispatch_Engine &&) = default;
+
+#ifndef CHAISCRIPT_NO_THREADS
+      /// Track an async thread so it can be joined during destruction
+      void track_async_thread(std::thread t_thread) {
+        chaiscript::detail::threading::unique_lock<chaiscript::detail::threading::shared_mutex> l(m_async_mutex);
+        // Clean up already-finished threads to avoid unbounded growth
+        m_async_threads.erase(
+            std::remove_if(m_async_threads.begin(), m_async_threads.end(),
+                           [](std::thread &t) { return !t.joinable(); }),
+            m_async_threads.end());
+        m_async_threads.push_back(std::move(t_thread));
+      }
+#endif
+
       /// \brief casts an object while applying any Dynamic_Conversion available
       template<typename Type>
       decltype(auto) boxed_cast(const Boxed_Value &bv) const {
@@ -1165,6 +1188,21 @@ namespace chaiscript {
         get_function_objects_int().insert_or_assign(t_name, std::move(new_func));
       }
 
+      void join_async_threads() {
+#ifndef CHAISCRIPT_NO_THREADS
+        std::vector<std::thread> threads;
+        {
+          chaiscript::detail::threading::unique_lock<chaiscript::detail::threading::shared_mutex> l(m_async_mutex);
+          threads = std::move(m_async_threads);
+        }
+        for (auto &t : threads) {
+          if (t.joinable()) {
+            t.join();
+          }
+        }
+#endif
+      }
+
       mutable chaiscript::detail::threading::shared_mutex m_mutex;
 
       Type_Conversions m_conversions;
@@ -1174,6 +1212,11 @@ namespace chaiscript {
       mutable std::atomic_uint_fast32_t m_method_missing_loc = {0};
 
       State m_state;
+
+#ifndef CHAISCRIPT_NO_THREADS
+      mutable chaiscript::detail::threading::shared_mutex m_async_mutex;
+      std::vector<std::thread> m_async_threads;
+#endif
     };
 
     class Dispatch_State {

include/chaiscript/dispatchkit/proxy_functions.hpp

@@ -798,6 +798,14 @@ namespace chaiscript {
               ++numdiffs;
             }
           }
+
+          // Deprioritize functions whose first parameter (object/receiver) requires
+          // type conversion: conversions create temporaries, so mutations on the
+          // converted object are silently lost.
+          if (plist.size() > 1 && !func->get_param_types()[1].bare_equal(plist[0].get_type_info())) {
+            numdiffs = plist.size();
+          }
+
           ordered_funcs.emplace_back(numdiffs, func.get());
         }
       }

include/chaiscript/language/chaiscript_engine.hpp

@@ -15,6 +15,7 @@
 #include <exception>
 #include <fstream>
 #include <functional>
+#include <future>
 #include <map>
 #include <memory>
 #include <mutex>
@@ -190,6 +191,25 @@ namespace chaiscript {
                    }),
                    "namespace");
       m_engine.add(fun([this](const std::string &t_namespace_name) { import(t_namespace_name); }), "import");
+
+#ifndef CHAISCRIPT_NO_THREADS
+      // Register async() with thread tracking so the engine can join all
+      // async threads before destroying shared state (issues #632, #636).
+      m_engine.add(chaiscript::fun(
+                       [this](const std::function<chaiscript::Boxed_Value()> &t_func) {
+                         auto promise_ptr = std::make_shared<std::promise<chaiscript::Boxed_Value>>();
+                         auto future = promise_ptr->get_future();
+                         m_engine.track_async_thread(std::thread([promise_ptr, t_func]() {
+                           try {
+                             promise_ptr->set_value(t_func());
+                           } catch (...) {
+                             promise_ptr->set_exception(std::current_exception());
+                           }
+                         }));
+                         return future;
+                       }),
+                   "async");
+#endif
     }
 
     /// Skip BOM at the beginning of file

unittests/async_engine_lifetime.chai

@@ -0,0 +1,17 @@
+// Regression test for #632 and #636: Heap-use-after-free in async threads
+// Async threads must complete before the engine is destroyed.
+
+var func = fun(){
+  var ret = 0;
+  for (var i = 0; i < 1000; ++i) {
+    ret += i;
+  }
+  return ret;
+}
+
+var fut1 = async(func);
+var fut2 = async(func);
+
+// Wait for results to verify correctness
+assert_equal(fut1.get(), 499500);
+assert_equal(fut2.get(), 499500);

unittests/async_engine_lifetime_test.cpp

@@ -0,0 +1,46 @@
+// Regression test for #632 and #636:
+// Heap-use-after-free when async threads outlive the ChaiScript engine.
+// The engine must join all outstanding async threads before destroying shared state.
+
+#include <chaiscript/chaiscript.hpp>
+
+int main() {
+  // Test 1: Async threads still running when engine is destroyed.
+  // Without the fix, this triggers heap-use-after-free under ASAN/TSAN.
+  for (int iter = 0; iter < 3; ++iter) {
+    {
+      chaiscript::ChaiScript chai;
+      try {
+        chai.eval(R"(
+          var func = fun(){
+            var ret = 0;
+            for (var i = 0; i < 5000; ++i) {
+              ret += i;
+            }
+            return ret;
+          }
+
+          var fut1 = async(func);
+          var fut2 = async(func);
+        )");
+        // Engine destroyed here without waiting for futures.
+      } catch (const std::exception &) {
+        // Exceptions are fine
+      }
+    }
+  }
+
+  // Test 2: Verify async still works correctly (results are accessible).
+  {
+    chaiscript::ChaiScript chai;
+    auto result = chai.eval<int>(R"(
+      var f = async(fun() { return 42; });
+      f.get();
+    )");
+    if (result != 42) {
+      return EXIT_FAILURE;
+    }
+  }
+
+  return EXIT_SUCCESS;
+}

unittests/compiled_tests.cpp

@@ -1502,6 +1502,68 @@ TEST_CASE("IO redirection different instances are independent") {
   CHECK(output2 == "from2");
 }
 
+// Regression test: push_back() on script-created vector has no effect when
+// vector_conversion is in effect. The bug occurs because dispatch selects
+// the C++ push_back for the converted type over the built-in one, operating
+// on a temporary copy of the vector.
+TEST_CASE("push_back on script vector with vector_conversion") {
+  chaiscript::ChaiScript_Basic chai(create_chaiscript_stdlib(), create_chaiscript_parser());
+
+  auto m = std::make_shared<chaiscript::Module>();
+  chaiscript::bootstrap::standard_library::vector_type<std::vector<std::string>>("VectorString", *m);
+  m->add(chaiscript::vector_conversion<std::vector<std::string>>());
+  chai.add(m);
+
+  // Register a C++ function that accepts the converted type, so we can
+  // verify that vector_conversion actually works for passing vectors
+  chai.add(chaiscript::fun([](const std::vector<std::string> &v) -> std::string {
+    std::string result;
+    for (const auto &s : v) {
+      if (!result.empty()) { result += ","; }
+      result += s;
+    }
+    return result;
+  }), "join_strings");
+
+  // push_back on an empty script-created vector must be visible
+  CHECK(chai.eval<bool>(
+    "auto x = [];"
+    "x.push_back(\"Hello\");"
+    "x.size() == 1"
+  ));
+
+  // push_back on a vector with initial elements must grow correctly
+  CHECK(chai.eval<bool>(
+    "auto y = [\"a\", \"b\"];"
+    "y.push_back(\"c\");"
+    "y.push_back(\"d\");"
+    "y.size() == 4"
+  ));
+
+  // Verify the actual content is preserved after push_back
+  CHECK(chai.eval<std::string>(
+    "auto z = [];"
+    "z.push_back(\"World\");"
+    "z[0]"
+  ) == "World");
+
+  // Round-trip: build a vector in script, push_back elements, then pass it
+  // to a C++ function via vector_conversion and verify the contents
+  CHECK(chai.eval<std::string>(
+    "auto v = [\"one\", \"two\"];"
+    "v.push_back(\"three\");"
+    "join_strings(v)"
+  ) == "one,two,three");
+
+  // Verify conversion works on a freshly created vector too
+  CHECK(chai.eval<std::string>(
+    "auto w = [];"
+    "w.push_back(\"hello\");"
+    "w.push_back(\"world\");"
+    "join_strings(w)"
+  ) == "hello,world");
+}
+
 // Regression test for issue #607: AST_Node_Trace must be a complete type
 // when used in eval_error's std::vector<AST_Node_Trace> call_stack member.
 // This failed to compile with C++20 on clang/libc++ when AST_Node_Trace

unittests/conversion_functions.chai

@@ -0,0 +1,33 @@
+// Test that all conversion functions work across char, int, and string types
+
+// char() constructor
+assert_equal('A', char('A'))   // char from char (identity via Boxed_Number)
+assert_equal('A', char(65))    // char from int (via Boxed_Number)
+assert_equal('A', char("A"))   // char from string (new)
+
+// to_char() conversions
+assert_equal('A', to_char('A'))   // to_char from char (identity)
+assert_equal('A', to_char(65))    // to_char from int (new, via Boxed_Number)
+assert_equal('A', to_char("A"))   // to_char from string (existing)
+
+// int() constructor
+assert_equal(65, int('A'))   // int from char (via Boxed_Number)
+assert_equal(65, int(65))    // int from int (identity via Boxed_Number)
+assert_equal(65, int("65"))  // int from string (new)
+
+// to_int() conversions
+assert_equal(65, to_int('A'))    // to_int from char (new, via Boxed_Number)
+assert_equal(65, to_int(65))     // to_int from int (identity)
+assert_equal(65, to_int("65"))   // to_int from string (existing)
+
+// to_string() conversions
+assert_equal("A", to_string('A'))
+assert_equal("65", to_string(65))
+assert_equal("A", to_string("A"))
+
+// double conversions
+assert_equal(3.5, double("3.5"))       // double from string (new)
+assert_equal(3.5, to_double("3.5"))    // to_double from string (existing)
+assert_equal(65.0, to_double('A'))     // to_double from char (new, via Boxed_Number)
+assert_equal(65.0, to_double(65))      // to_double from int (new, via Boxed_Number)
+assert_equal("3.5", to_string(3.5))    // to_string from double (existing)

unittests/emscripten_eval_test.cpp

@@ -0,0 +1,51 @@
+// Test that validates the eval patterns used by the Emscripten wrapper.
+// Based on work by Rob Loach (https://github.com/RobLoach/ChaiScript.js)
+
+#ifndef CHAISCRIPT_NO_THREADS
+#define CHAISCRIPT_NO_THREADS
+#endif
+
+#ifndef CHAISCRIPT_NO_DYNLOAD
+#define CHAISCRIPT_NO_DYNLOAD
+#endif
+
+#include <chaiscript/chaiscript.hpp>
+#include "../emscripten/chaiscript_eval.hpp"
+#include <cassert>
+#include <cmath>
+#include <string>
+
+int main() {
+  // Test eval (void return) - same as Emscripten eval()
+  chaiscript_eval("var x = 42");
+
+  // Test evalString - same as Emscripten evalString()
+  std::string s = chaiscript_eval_string("to_string(x)");
+  assert(s == "42");
+
+  // Test evalInt - same as Emscripten evalInt()
+  int i = chaiscript_eval_int("1 + 2");
+  assert(i == 3);
+
+  // Test evalBool - same as Emscripten evalBool()
+  bool b = chaiscript_eval_bool("true");
+  assert(b == true);
+
+  b = chaiscript_eval_bool("false");
+  assert(b == false);
+
+  // Test evalFloat - same as Emscripten evalFloat()
+  float f = chaiscript_eval_float("1.5f");
+  assert(std::abs(f - 1.5f) < 0.001f);
+
+  // Test evalDouble - same as Emscripten evalDouble()
+  double d = chaiscript_eval_double("3.14");
+  assert(std::abs(d - 3.14) < 0.001);
+
+  // Test a more complex expression
+  chaiscript_eval("def square(n) { return n * n; }");
+  int sq = chaiscript_eval_int("square(7)");
+  assert(sq == 49);
+
+  return 0;
+}