[libc++] Promote GCC 11 to mandatory CI

Also, fix the last issue that prevented GCC 11 from passing the test
suite. Thanks to everyone else who fixed issues.

Differential Revision: https://reviews.llvm.org/D104315

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_is_lock_free.pass.cpp

@@ -12,12 +12,10 @@
 // <atomic>
 
 // template <class T>
-//     bool
-//     atomic_is_lock_free(const volatile atomic<T>* obj);
+// bool atomic_is_lock_free(const volatile atomic<T>* obj);
 //
 // template <class T>
-//     bool
-//     atomic_is_lock_free(const atomic<T>* obj);
+// bool atomic_is_lock_free(const atomic<T>* obj);
 
 #include <atomic>
 #include <cassert>
@@ -29,23 +27,20 @@ template <class T>
 struct TestFn {
   void operator()() const {
     typedef std::atomic<T> A;
-    A t;
+    A t = T();
     bool b1 = std::atomic_is_lock_free(static_cast<const A*>(&t));
-    volatile A vt;
+    volatile A vt = T();
     bool b2 = std::atomic_is_lock_free(static_cast<const volatile A*>(&vt));
     assert(b1 == b2);
   }
 };
 
-struct A
-{
-    char _[4];
+struct A {
+  char x[4];
 };
 
-int main(int, char**)
-{
-    TestFn<A>()();
-    TestEachAtomicType<TestFn>()();
-
+int main(int, char**) {
+  TestFn<A>()();
+  TestEachAtomicType<TestFn>()();
   return 0;
 }

libcxx/utils/ci/Dockerfile

@@ -58,11 +58,9 @@ RUN . /tmp/env.sh && apt-get install -y clang-format-$LLVM_VERSION
 RUN ln -s $(find /usr/bin -regex '^.+/clang-format-[0-9.]+$') /usr/bin/clang-format && [ -e $(readlink /usr/bin/clang-format) ]
 RUN ln -s $(find /usr/bin -regex '^.+/git-clang-format-[0-9.]+$') /usr/bin/git-clang-format && [ -e $(readlink /usr/bin/git-clang-format) ]
 
-# Install a recent GCC
+# Install the most recent GCC version and the previous one (which are the two we support)
 RUN add-apt-repository ppa:ubuntu-toolchain-r/test
 RUN apt-get update && apt install -y gcc-10 g++-10 gcc-11 g++-11
-RUN ln -f -s /usr/bin/g++-10 /usr/bin/g++ && [ -e $(readlink /usr/bin/g++) ]
-RUN ln -f -s /usr/bin/gcc-10 /usr/bin/gcc && [ -e $(readlink /usr/bin/gcc) ]
 
 # Install a recent CMake
 RUN wget https://github.com/Kitware/CMake/releases/download/v3.18.2/cmake-3.18.2-Linux-x86_64.sh -O /tmp/install-cmake.sh

libcxx/utils/ci/buildkite-pipeline.yml

@@ -124,7 +124,7 @@ steps:
         - exit_status: -1  # Agent was lost
           limit: 2
 
-  - label: "GCC/C++20"
+  - label: "GCC Current/C++20"
     command: "libcxx/utils/ci/run-buildbot generic-gcc"
     artifact_paths:
       - "**/test-results.xml"
@@ -135,8 +135,13 @@ steps:
         - exit_status: -1  # Agent was lost
           limit: 2
 
-  - label: "GCC-next/C++20"
-    command: "libcxx/utils/ci/run-buildbot generic-gcc-next"
+  #
+  # All other supported configurations of libc++.
+  #
+  - wait
+
+  - label: "GCC Previous/C++20"
+    command: "libcxx/utils/ci/run-buildbot generic-gcc-prev"
     artifact_paths:
       - "**/test-results.xml"
     agents:
@@ -145,13 +150,6 @@ steps:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
-    soft_fail:
-      - exit_status: 1
-
-  #
-  # All other supported configurations of libc++.
-  #
-  - wait
 
   - label: "-fno-exceptions"
     command: "libcxx/utils/ci/run-buildbot generic-noexceptions"

libcxx/utils/ci/run-buildbot

@@ -279,15 +279,15 @@ generic-32bit)
     check-cxx-cxxabi
 ;;
 generic-gcc)
-    export CC=gcc
-    export CXX=g++
+    export CC=gcc-11
+    export CXX=g++-11
     clean
     generate-cmake
     check-cxx-cxxabi
 ;;
-generic-gcc-next)
-    export CC=gcc-11
-    export CXX=g++-11
+generic-gcc-prev)
+    export CC=gcc-10
+    export CXX=g++-10
     clean
     generate-cmake
     check-cxx-cxxabi

libcxxabi/test/catch_member_function_pointer_02.pass.cpp

@@ -12,7 +12,7 @@
 
 // GCC 7 and 8 support noexcept function types but this test still fails.
 // This is likely a bug in their implementation. Investigation needed.
-// XFAIL: gcc-7, gcc-8, gcc-9, gcc-10
+// XFAIL: gcc-7, gcc-8, gcc-9, gcc-10, gcc-11
 
 #include <cassert>