Crafter.Build/tests/WasmExceptions/main.cpp

// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

// C++ exceptions in a wasm build, run under wasmtime: the fixture throws
// through frames whose destructors have to run, catches the exception,
// catches one from a libc++ header (vector::at) and one thrown inside
// libc++.a itself (stoi), and with an argument lets one escape main, which
// has to end the run as an uncaught exception rather than exit 0, trap or
// hang. Its C source uses setjmp, which compiles and links next to the C++
// objects only when C gets the same wasm flags.
//
// wasm builds used to be compiled with -fno-exceptions, so a throw did not
// compile and libc++'s own throws aborted. Each part of turning them on fails
// in its own way, and this is the test that sees it: a std module or a unit
// built without exceptions (clang rejects the BMI), a link without libunwind
// (undefined __cpp_exception), the libc++ built without exceptions (stoi
// aborts), or LLVM's default legacy encoding, which wasmtime refuses to load.
// Skips like WasmHelloRuns when there is no exception-enabled WASI sysroot or
// no wasmtime; inside the Flatpak both are bundled.
namespace {
    std::int32_t failures = 0;

    void Check(bool cond, std::string_view msg) {
        if (!cond) {
            std::println(std::cerr, "FAIL: {}", msg);
            ++failures;
        }
    }
}

int main() {
    const Toolchain& tc = GetToolchain();
    const fs::path libDir = tc.wasiSysroot / "lib" / "wasm32-wasip1";
    if (!fs::exists(libDir / "eh" / "libunwind.a") && !fs::exists(libDir / "libunwind.a")) {
        std::println(std::cerr, "SKIP: no exception-enabled WASI sysroot at {}", tc.wasiSysroot.string());
        return 77;
    }
    if (std::system("which wasmtime > /dev/null 2>&1") != 0) {
        std::println(std::cerr, "SKIP: wasmtime not on PATH");
        return 77;
    }

    Configuration cfg;
    cfg.path = fs::current_path() / "tests" / "WasmExceptions" / "fixture";
    cfg.name = "wasm-exceptions";
    cfg.outputName = "wasm-exceptions";
    cfg.target = "wasm32-wasip1";
    cfg.type = ConfigurationType::Executable;
    std::array<fs::path, 0> ifaces = {};
    std::array<fs::path, 1> impls = { "main" };
    cfg.GetInterfacesAndImplementations(ifaces, impls);
    cfg.cFiles = { cfg.path / "jump" };
    // setjmp and longjmp live in libsetjmp, which the build does not link
    // on its own.
    cfg.linkFlags.push_back("-lsetjmp");

    std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
    std::mutex depMutex;
    const BuildResult r = Build(cfg, depResults, depMutex);
    if (!r.result.empty()) {
        std::println(std::cerr, "build failed: {}", r.result);
        return 1;
    }
    const fs::path wasm = ExpectedOutput(cfg);

    const auto caught = RunCommandWithTimeout(std::format("wasmtime {}", wasm.string()), std::chrono::seconds(60));
    Check(caught.exitCode == 0, std::format("the run that catches everything exits 0 (exit {}): {}", caught.exitCode, caught.output));
    Check(caught.output.contains("caught: thrown in wasm after 4 destructors"), std::format("the exception is caught after unwinding all four frames: {}", caught.output));
    Check(caught.output.contains("caught: out_of_range from libc++"), std::format("an exception from a libc++ header is catchable: {}", caught.output));
    Check(caught.output.contains("caught: invalid_argument from inside libc++"), std::format("an exception from inside libc++.a is catchable: {}", caught.output));
    Check(caught.output.contains("longjmp came back with 7"), std::format("setjmp in a C source works next to the C++ objects: {}", caught.output));

    const auto escaped = RunCommandWithTimeout(std::format("wasmtime {} uncaught", wasm.string()), std::chrono::seconds(60));
    Check(escaped.exitCode != 0 && !escaped.timedOut && !escaped.crashed && escaped.output.contains("thrown Wasm exception"), std::format("an exception escaping main ends the run as an uncaught exception (exit {}): {}", escaped.exitCode, escaped.output));

    if (failures > 0) {
        std::println(std::cerr, "{} assertions failed", failures);
        return 1;
    }
    return 0;
}