cxx-qt-gen: allow for unused unsafe blocks and resolve no-exception issues

CHANGELOG.md

@@ -17,6 +17,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/KDAB/cxx-qt/compare/v0.7.0...HEAD)
 
+### Fixed
+
+- Build warnings due to unused unsafe blocks since CXX 1.0.130
+- Build failures with WASM due to `cc` crate setting `-fno-exceptions` since 1.2.0
+
 ## [0.7.0](https://github.com/KDAB/cxx-qt/compare/v0.6.1...v0.7.0) - 2024-10-30
 
 ### Added

Cargo.toml

@@ -58,4 +58,9 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 
 [workspace.lints.clippy]
-incompatible_msrv = "deny"
+incompatible_msrv = "deny"
+
+[patch.crates-io]
+cxx = { git = 'https://github.com/ahayzen-kdab/cxx.git', branch = "trycatch-no-exceptions" }
+cxx-build = { git = 'https://github.com/ahayzen-kdab/cxx.git', branch = "trycatch-no-exceptions" }
+cxx-gen = { git = 'https://github.com/ahayzen-kdab/cxx.git', branch = "trycatch-no-exceptions" }

book/src/concepts/wasm-builds.md

@@ -190,3 +190,12 @@ error[E0433]: failed to resolve: use of undeclared type `IovLen`
 `socket2` is a dependency of `async-io`, which is a dependency of `async-std`.
 
 There is discussion around supporting wasm in the GitHub repository for `async-std`, and the progress is being tracked [here](https://github.com/async-rs/async-std/issues/220).
+
+### Cannot use throw / try catch with exceptions disabled
+
+CXX and CXX-Qt can generate code that attempts to use exceptions but these are disabled
+for most WASM platforms.
+
+The cmake-qt-cmake builder will attempt to set a define of `RUST_CXX_NO_EXCEPTIONS` which should
+causes the code not to be compiled. But if this doesn't work try adding `-DRUST_CXX_NO_EXCEPTIONS`
+to a `CXXFLAGS` enviornment variable while building.

crates/cxx-qt-gen/src/generator/rust/mod.rs

@@ -78,6 +78,10 @@ impl GeneratedRustBlocks {
         );
         let cxx_mod = parse_quote! {
             #[cxx::bridge(namespace = #namespace)]
+            // We need to allow for unused unsafe otherwise we get build failures
+            // due to changes in CXX 1.0.130
+            // https://github.com/dtolnay/cxx/commit/46fedc68464f80587057c436b4f6b6debeb9f714
+            #[allow(unused_unsafe)]
             #(#docs)*
             #module
         };

crates/cxx-qt-gen/test_outputs/inheritance.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "")]
+#[allow(unused_unsafe)]
 mod inheritance {
     extern "C++" {
         include!("cxx-qt-lib/qmodelindex.h");

crates/cxx-qt-gen/test_outputs/invokables.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "cxx_qt::my_object")]
+#[allow(unused_unsafe)]
 mod ffi {
     #[namespace = ""]
     unsafe extern "C++" {

crates/cxx-qt-gen/test_outputs/passthrough_and_naming.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "cxx_qt::multi_object")]
+#[allow(unused_unsafe)]
 pub mod ffi {
     const MAX: u16 = 65535;
     enum Event {

crates/cxx-qt-gen/test_outputs/properties.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "cxx_qt::my_object")]
+#[allow(unused_unsafe)]
 mod ffi {
     #[namespace = ""]
     unsafe extern "C++" {

crates/cxx-qt-gen/test_outputs/qenum.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "cxx_qt::my_object")]
+#[allow(unused_unsafe)]
 mod ffi {
     unsafe extern "C++" {
         include ! (< QtCore / QObject >);

crates/cxx-qt-gen/test_outputs/signals.rs

@@ -1,4 +1,5 @@
 #[cxx::bridge(namespace = "cxx_qt::my_object")]
+#[allow(unused_unsafe)]
 mod ffi {
     #[namespace = ""]
     unsafe extern "C++" {

crates/cxx-qt-lib/include/core/qanystringview.h

@@ -27,10 +27,6 @@ namespace cxxqtlib1 {
 
 QAnyStringView
 qanystringviewInitFromRustString(::rust::Str string);
-QAnyStringView
-qanystringviewInitFromQString(const QString& string);
-::rust::String
-qanystringviewToRustString(const QAnyStringView& string);
 
 ::rust::isize
 qanystringviewLen(const QAnyStringView& string);

crates/cxx-qt-lib/src/core/qanystringview.cpp

@@ -32,12 +32,6 @@ qanystringviewInitFromRustString(::rust::Str string)
   return QAnyStringView(string.data(), string.size());
 }
 
-QAnyStringView
-qanystringviewInitFromQString(const QString& string)
-{
-  return QAnyStringView(string);
-}
-
 ::rust::isize
 qanystringviewLen(const QAnyStringView& string)
 {

crates/cxx-qt-lib/src/core/qanystringview.rs

@@ -2,7 +2,7 @@
 // SPDX-FileContributor: Joshua Goins <[email protected]>
 //
 // SPDX-License-Identifier: MIT OR Apache-2.0
-use crate::QString;
+use crate::{QByteArray, QString};
 use core::ffi::c_void;
 use core::marker::PhantomData;
 use core::mem::MaybeUninit;
@@ -14,6 +14,9 @@ mod ffi {
         include!("cxx-qt-lib/qanystringview.h");
         type QAnyStringView<'a> = super::QAnyStringView<'a>;
 
+        include!("cxx-qt-lib/qbytearray.h");
+        type QByteArray = crate::QByteArray;
+
         include!("cxx-qt-lib/qstring.h");
         type QString = crate::QString;
 
@@ -24,6 +27,10 @@ mod ffi {
         /// Returns true if this string is null; otherwise returns false.
         #[rust_name = "is_null"]
         fn isNull(self: &QAnyStringView) -> bool;
+
+        /// Returns a deep copy of this string view's data as a QString.
+        #[rust_name = "to_qstring"]
+        fn toString(self: &QAnyStringView) -> QString;
     }
 
     #[namespace = "rust::cxxqtlib1"]
@@ -35,13 +42,16 @@ mod ffi {
         fn construct() -> QAnyStringView<'static>;
         #[doc(hidden)]
         #[rust_name = "QAnyStringView_init_from_rust_string"]
-        fn qanystringviewInitFromRustString<'a>(string: &str) -> QAnyStringView<'a>;
+        fn qanystringviewInitFromRustString<'a>(string: &'a str) -> QAnyStringView<'a>;
+        #[doc(hidden)]
+        #[rust_name = "QAnyStringView_init_from_qbytearray"]
+        fn construct<'a>(bytes: &'a QByteArray) -> QAnyStringView<'a>;
         #[doc(hidden)]
         #[rust_name = "QAnyStringView_init_from_qstring"]
-        fn qanystringviewInitFromQString<'a>(string: &QString) -> QAnyStringView<'a>;
+        fn construct<'a>(string: &'a QString) -> QAnyStringView<'a>;
         #[doc(hidden)]
         #[rust_name = "QAnyStringView_init_from_QAnyStringView"]
-        fn construct<'a>(string: &QAnyStringView) -> QAnyStringView<'a>;
+        fn construct<'a>(string: &QAnyStringView<'a>) -> QAnyStringView<'a>;
 
         #[doc(hidden)]
         #[rust_name = "QAnyStringView_eq"]
@@ -90,14 +100,21 @@ impl Eq for QAnyStringView<'_> {}
 
 impl<'a> From<&'a str> for QAnyStringView<'a> {
     /// Constructs a QAnyStringView from a Rust string
-    fn from(str: &str) -> Self {
+    fn from(str: &'a str) -> Self {
         ffi::QAnyStringView_init_from_rust_string(str)
     }
 }
 
-impl From<&QString> for QAnyStringView<'_> {
+impl<'a> From<&'a QByteArray> for QAnyStringView<'a> {
+    /// Constructs a QAnyStringView from a QByteArray
+    fn from(bytes: &'a QByteArray) -> Self {
+        ffi::QAnyStringView_init_from_qbytearray(bytes)
+    }
+}
+
+impl<'a> From<&'a QString> for QAnyStringView<'a> {
     /// Constructs a QAnyStringView from a QString
-    fn from(string: &QString) -> Self {
+    fn from(string: &'a QString) -> Self {
         ffi::QAnyStringView_init_from_qstring(string)
     }
 }

crates/cxx-qt/include/thread.h

@@ -6,6 +6,7 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 #pragma once
 
+#include <iostream>
 #include <memory>
 #include <mutex>
 #include <shared_mutex>
@@ -58,8 +59,14 @@ class CxxQtThread final
     // Ensure that we can read the pointer and it's not being written to
     const auto guard = ::std::shared_lock(m_obj->mutex);
     if (!m_obj->ptr) {
+#if defined(RUST_CXX_NO_EXCEPTIONS)
+      std::cerr << "Cannot queue function pointer as object has been destroyed"
+                << std::endl;
+      std::abort();
+#else
       throw ::std::runtime_error(
         "Cannot queue function pointer as object has been destroyed");
+#endif
       return;
     }
 
@@ -81,8 +88,15 @@ class CxxQtThread final
     // Add the lambda to the queue
     if (!QMetaObject::invokeMethod(
           m_obj->ptr, ::std::move(lambda), Qt::QueuedConnection)) {
+#if defined(RUST_CXX_NO_EXCEPTIONS)
+      std::cerr
+        << "Cannot queue function pointer as invokeMethod on object failed"
+        << std::endl;
+      std::abort();
+#else
       throw ::std::runtime_error(
         "Cannot queue function pointer as invokeMethod on object failed");
+#endif
     }
   }
 

examples/demo_threading/CMakeLists.txt

@@ -46,7 +46,8 @@ if(NOT CxxQt_FOUND)
     FetchContent_Declare(
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
     )
 
     FetchContent_MakeAvailable(CxxQt)

examples/qml_features/CMakeLists.txt

@@ -46,7 +46,8 @@ if(NOT CxxQt_FOUND)
     FetchContent_Declare(
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
     )
 
     FetchContent_MakeAvailable(CxxQt)

examples/qml_minimal/CMakeLists.txt

@@ -55,7 +55,8 @@ if(NOT CxxQt_FOUND)
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
         # ANCHOR_END: book_cmake_find_cxx_qt_start
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
         # ANCHOR: book_cmake_find_cxx_qt_end
     )
 

tests/basic_cxx_only/CMakeLists.txt

@@ -36,7 +36,8 @@ if(NOT CxxQt_FOUND)
     FetchContent_Declare(
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
     )
 
     FetchContent_MakeAvailable(CxxQt)

tests/basic_cxx_qt/CMakeLists.txt

@@ -36,7 +36,8 @@ if(NOT CxxQt_FOUND)
     FetchContent_Declare(
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
     )
 
     FetchContent_MakeAvailable(CxxQt)

tests/qt_types_standalone/CMakeLists.txt

@@ -36,7 +36,8 @@ if(NOT CxxQt_FOUND)
     FetchContent_Declare(
         CxxQt
         GIT_REPOSITORY https://github.com/kdab/cxx-qt-cmake.git
-        GIT_TAG main
+        GIT_TAG wasm-set-cxxflags
+        # GIT_TAG main
     )
 
     FetchContent_MakeAvailable(CxxQt)

tests/qt_types_standalone/rust/src/qanystringview.rs

@@ -20,17 +20,27 @@ mod qanystringview_cxx {
 
     extern "Rust" {
         fn construct_qanystringview(str: &str) -> QAnyStringView;
+    }
+
+    // This method must be unsafe otherwise we hit
+    // must be `unsafe fn` in order to expose explicit lifetimes to C++
+    //
+    // But then Rust complains about unused unsafe so we need to allow for this
+    #[allow(unused_unsafe)]
+    extern "Rust" {
         unsafe fn construct_qanystringview_qstring<'a>(str: &'a QString) -> QAnyStringView<'a>;
-        unsafe fn clone_qanystringview<'a>(l: &'a QAnyStringView) -> QAnyStringView<'a>;
+        unsafe fn clone_qanystringview<'a>(l: &QAnyStringView<'a>) -> QAnyStringView<'a>;
     }
 }
 
-fn construct_qanystringview(str: &str) -> QAnyStringView {
+fn construct_qanystringview<'a>(str: &'a str) -> QAnyStringView<'a> {
     QAnyStringView::from(str)
 }
-fn construct_qanystringview_qstring(str: &QString) -> QAnyStringView {
+
+fn construct_qanystringview_qstring<'a>(str: &'a QString) -> QAnyStringView<'a> {
     QAnyStringView::from(str)
 }
-fn clone_qanystringview<'a>(l: &'a QAnyStringView) -> QAnyStringView<'a> {
+
+fn clone_qanystringview<'a>(l: &QAnyStringView<'a>) -> QAnyStringView<'a> {
     l.clone()
 }