From 7c3fde0837281962f052004bb6ed7eb64739d9b7 Mon Sep 17 00:00:00 2001
From: Andrew Hayzen <andrew.hayzen@kdab.com>
Date: Fri, 15 Nov 2024 15:39:07 +0000
Subject: [PATCH 1/2] trycatch: do not try catch when no exceptions is enabled

For WASM targets the `cc` crate changed to always set `-fno-exceptions`,
before only `-fignore-exceptions` was being set elsewhere, so now programs
fail to build when using `cxx` if any `throw` or `try ... catch` are used.

> error: cannot use 'try' with exceptions disabled

Instead for trycatch just call `func()`.
---
 book/src/binding/result.md | 12 +++++++++---
 gen/src/builtin.rs         | 12 +++++++++---
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/book/src/binding/result.md b/book/src/binding/result.md
index 733212a63..856d49ae7 100644
--- a/book/src/binding/result.md
+++ b/book/src/binding/result.md
@@ -137,10 +137,16 @@ you'd like for the Rust error to have.
 ...namespace behavior {
 ...
 template <typename Try, typename Fail>
-static void trycatch(Try &&func, Fail &&fail) noexcept try {
+static void trycatch(Try &&func, Fail &&fail) noexcept {
+#if defined(RUST_CXX_NO_EXCEPTIONS)
   func();
-} catch (const std::exception &e) {
-  fail(e.what());
+#else
+  try {
+    func();
+  } catch (const std::exception &e) {
+    fail(e.what());
+  }
+#endif
 }
 ...
 ...} // namespace behavior
diff --git a/gen/src/builtin.rs b/gen/src/builtin.rs
index d38473afc..37c33709b 100644
--- a/gen/src/builtin.rs
+++ b/gen/src/builtin.rs
@@ -410,10 +410,16 @@ pub(super) fn write(out: &mut OutFile) {
             "    ::std::is_same<decltype(trycatch(::std::declval<Try>(), ::std::declval<Fail>())),",
         );
         writeln!(out, "                 missing>::value>::type");
-        writeln!(out, "trycatch(Try &&func, Fail &&fail) noexcept try {{");
+        writeln!(out, "trycatch(Try &&func, Fail &&fail) noexcept {{");
+        writeln!(out, "#if defined(RUST_CXX_NO_EXCEPTIONS)");
         writeln!(out, "  func();");
-        writeln!(out, "}} catch (::std::exception const &e) {{");
-        writeln!(out, "  fail(e.what());");
+        writeln!(out, "#else");
+        writeln!(out, "  try {{");
+        writeln!(out, "    func();");
+        writeln!(out, "  }} catch (::std::exception const &e) {{");
+        writeln!(out, "    fail(e.what());");
+        writeln!(out, "  }}");
+        writeln!(out, "#endif");
         writeln!(out, "}}");
         out.end_block(Block::Namespace("behavior"));
     }

From 7a0f3f2e3c8dc44f9c74b2f6e6165354239b63a8 Mon Sep 17 00:00:00 2001
From: Andrew Hayzen <andrew.hayzen@kdab.com>
Date: Fri, 15 Nov 2024 15:54:45 +0000
Subject: [PATCH 2/2] result: without exception do not throw when Result Err
 just abort

For WASM targets the `cc` crate changed to always set `-fno-exceptions`,
before only `-fignore-exceptions` was being set elsewhere, so now programs
fail to build when using `cxx` if any `throw` or `try ... catch` are used.

> error: cannot use 'throw' with exceptions disabled

Instead of throwing just abort.
---
 gen/src/write.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gen/src/write.rs b/gen/src/write.rs
index 77e1da0b2..7d3d5380d 100644
--- a/gen/src/write.rs
+++ b/gen/src/write.rs
@@ -1123,7 +1123,19 @@ fn write_rust_function_shim_impl(
     if sig.throws {
         out.builtin.rust_error = true;
         writeln!(out, "  if (error$.ptr) {{");
+        writeln!(out, "#if defined(RUST_CXX_NO_EXCEPTIONS)");
+        writeln!(
+            out,
+            "    const auto msg = static_cast<char const *>(error$.ptr);"
+        );
+        writeln!(
+            out,
+            "    std::fprintf(stderr, \"Error: %s Aborting.\\n\", msg);"
+        );
+        writeln!(out, "    std::abort();");
+        writeln!(out, "#else");
         writeln!(out, "    throw ::rust::impl<::rust::Error>::error(error$);");
+        writeln!(out, "#endif");
         writeln!(out, "  }}");
     }
     if indirect_return {