Initial work on generating the toolchains.

package.json

@@ -24,6 +24,7 @@
     "url": "https://github.com/robertoraggi/cplusplus/issues"
   },
   "devDependencies": {
+    "@types/node": "^24.0.13",
     "jsonc-cli": "^1.0.2",
     "zx": "^8.6.1"
   },

scripts/update-toolchain.ts

@@ -0,0 +1,120 @@
+import { execFile } from "node:child_process";
+
+const machines = ["aarch64", "x86_64", "wasm32"] as const;
+const oses = ["linux", "macosx", "windows", "wasi"] as const;
+const compilers = ["c23", "c++26"];
+
+type Machine = (typeof machines)[number];
+type OS = (typeof oses)[number];
+type Compiler = (typeof compilers)[number];
+type Config = [machine: Machine, os: OS, compiler: Compiler];
+
+const configs: Config[] = [
+  ["aarch64", "linux", "c++26"],
+  ["aarch64", "linux", "c23"],
+  ["aarch64", "macosx", "c++26"],
+  ["aarch64", "macosx", "c23"],
+  ["aarch64", "windows", "c++26"],
+  ["aarch64", "windows", "c23"],
+  ["wasm32", "wasi", "c++26"],
+  ["wasm32", "wasi", "c23"],
+  ["x86_64", "linux", "c++26"],
+  ["x86_64", "linux", "c23"],
+  ["x86_64", "macosx", "c++26"],
+  ["x86_64", "macosx", "c23"],
+  ["x86_64", "windows", "c++26"],
+  ["x86_64", "windows", "c23"],
+];
+
+function configMatches({
+  config,
+  machine,
+  os,
+  compiler,
+}: {
+  config: Config;
+  machine?: Machine;
+  os?: OS;
+  compiler?: Compiler;
+}): boolean {
+  const [configMachine, configOS, configCompiler] = config;
+  return (
+    (machine ? configMachine === machine : true) &&
+    (os ? configOS === os : true) &&
+    (compiler ? configCompiler === compiler : true)
+  );
+}
+
+async function getPredefinedMacros({
+  config,
+}: {
+  config: Config;
+}): Promise<Set<string>> {
+  const [machine, os, compiler] = config;
+
+  const lang = compiler.startsWith("c++") ? "c++" : "c";
+  const target = `${machine}-${os}`;
+
+  return new Promise((resolve, reject) => {
+    execFile(
+      "clang",
+      [
+        `--target=${target}`,
+        "-E",
+        "-dM",
+        `-x${lang}`,
+        `-std=${compiler}`,
+        "/dev/null",
+      ],
+      (err, stdout) => {
+        if (err) {
+          reject(err);
+          return;
+        }
+
+        const predefinedMacros = stdout
+          .split("\n")
+          .map((line) => line.trim())
+          .filter(Boolean);
+
+        resolve(new Set(predefinedMacros));
+      }
+    );
+  });
+}
+
+async function main() {
+  const predefinedMacrosByConfig: Record<string, Set<string>> = {};
+  for (const config of configs) {
+    const predefinedMacros = await getPredefinedMacros({ config });
+    predefinedMacrosByConfig[config.join("-")] = predefinedMacros;
+    console.log(
+      `Config: ${config.join("-")} has ${predefinedMacros.size} predefined macros.`
+    );
+  }
+
+  machines.forEach((machine) => {
+    const machineConfigs = configs.filter((config) =>
+      configMatches({ config, machine })
+    );
+    const predefinedMacrosForMachine = machineConfigs.map((config) => {
+      return predefinedMacrosByConfig[config.join("-")];
+    });
+    return intersection(...predefinedMacrosForMachine);
+  });
+}
+
+function intersection<T>(...sets: Set<T>[]): Set<T> {
+  if (sets.length === 0) return new Set();
+  return sets.reduce((acc, set) => {
+    const intersection = new Set<T>();
+    for (const item of set) {
+      if (acc.has(item)) {
+        intersection.add(item);
+      }
+    }
+    return intersection;
+  }, sets[0]);
+}
+
+await main();

src/frontend/cxx/frontend.cc

@@ -117,8 +117,13 @@ auto readAll(const std::string& fileName) -> std::optional<std::string> {
 }
 
 void dumpTokens(const CLI& cli, TranslationUnit& unit, std::ostream& output) {
-  const auto lang =
-      cli.getSingle("-x") == "c" ? LanguageKind::kC : LanguageKind::kCXX;
+  auto lang = LanguageKind::kCXX;
+
+  if (auto x = cli.getSingle("x")) {
+    if (x == "c") lang = LanguageKind::kC;
+  } else if (unit.fileName().ends_with(".c")) {
+    lang = LanguageKind::kC;
+  }
 
   std::string flags;
 
@@ -158,7 +163,7 @@ auto runOnFile(const CLI& cli, const std::string& fileName) -> bool {
 
   const auto lang = cli.getSingle("-x");
 
-  if (lang == "c") {
+  if (lang == "c" || (!lang.has_value() && fileName.ends_with(".c"))) {
     // set the language to C
     preprocessor->setLanguage(LanguageKind::kC);
   }