use std::error_code instead of system::error_code

.drone.star

@@ -8,27 +8,126 @@
 # For Drone CI we use the Starlark scripting language to reduce duplication.
 # As the yaml syntax for Drone CI is rather limited.
 #
-#
+
+globalenv = {
+    'B2_CI_VERSION': '1',
+    'B2_VARIANT': 'debug,release',
+    'B2_FLAGS': 'warnings=extra warnings-as-errors=on',
+}
 
 def main(ctx):
-    return generate(
-        # Compilers
+    # generate() provides: main compiler matrix, asan, ubsan, coverage,
+    # and cmake-superproject (linux/latest gcc) by default
+    jobs = generate(
         [
-            'gcc >=10.0',
-            'clang >=10.0',
-            'msvc >=14.1',
-            'arm64-gcc latest',
-            's390x-gcc latest',
-            # 'freebsd-gcc latest',
-            'apple-clang *',
-            'arm64-clang latest',
-            's390x-clang latest',
-            'freebsd-clang latest',
-            'x86-msvc latest'
+            'gcc >=13.0',
+            'clang >=17.0',
+            # 'msvc >=14.1',
+            'arm64-clang latest'
+            # 'x86-msvc latest'
         ],
-        # Standards
         '>=20',
-        packages=['zlib1g', 'zlib1g-dev', 'libbrotli-dev'])
+        cmake=False,
+        docs=False,
+        coverage=False,
+        asan=False,
+        cache_dir='cache')
+    # Note: liburing-dev is not added to generate()'s package list.
+    # generate() emits jobs on Ubuntu focal (which has no liburing-dev
+    # package at all) and jammy (liburing 2.1, which our probe rejects
+    # for being too old). Either way io_uring stays disabled, so the
+    # install would just fail focal. The manual jobs below that target
+    # noble (24.04) explicitly install liburing-dev where it works.
+
+    # macOS: generate() skips apple-clang when cxx_range='>=20' because
+    # ci-automation's compiler_supports() doesn't list C++20 for apple-clang
+    # jobs += [
+    #     osx_cxx("macOS: Clang 16.2.0", "clang++", packages="",
+    #         buildscript="drone", buildtype="boost",
+    #         xcode_version="16.2.0",
+    #         environment={
+    #             'B2_TOOLSET': 'clang',
+    #             'B2_CXXSTD': '20',
+    #         },
+    #         globalenv=globalenv),
+    # 
+    #     osx_cxx("macOS: Clang 26.2.0", "clang++", packages="",
+    #         buildscript="drone", buildtype="boost",
+    #         xcode_version="26.2.0",
+    #         environment={
+    #             'B2_TOOLSET': 'clang',
+    #             'B2_CXXSTD': '20',
+    #         },
+    #         globalenv=globalenv),
+    # ]
+
+    # jobs += [
+    #     freebsd_cxx("clang-22", "clang++-22",
+    #         buildscript="drone", buildtype="boost",
+    #         freebsd_version="15.0",
+    #         environment={
+    #             'B2_TOOLSET': 'clang-22',
+    #             'B2_CXXSTD': '20',
+    #         },
+    #         globalenv=globalenv),
+    # ]
+
+    # Jobs not covered by generate()
+    jobs += [
+        # linux_cxx("Valgrind", "clang++-17", packages="clang-17 libc6-dbg libstdc++-12-dev liburing-dev",
+        #     llvm_os="jammy", llvm_ver="17",
+        #     buildscript="drone", buildtype="valgrind",
+        #     image="cppalliance/droneubuntu2204:1",
+        #     environment={
+        #         'COMMENT': 'valgrind',
+        #         'B2_TOOLSET': 'clang-17',
+        #         'B2_CXXSTD': '20',
+        #         'B2_DEFINES': 'BOOST_NO_STRESS_TEST=1',
+        #         'B2_VARIANT': 'debug',
+        #         'B2_TESTFLAGS': 'testing.launcher=valgrind',
+        #         'VALGRIND_OPTS': '--error-exitcode=1',
+        #     },
+        #     globalenv=globalenv),
+
+        # Note: no liburing-dev on the Drone cmake jobs even though the
+        # noble image has 2.5+. Docker's default seccomp profile blocks
+        # the io_uring_setup syscall (post-CVE hardening), so io_uring
+        # tests would compile in but abort at runtime with EPERM
+        # ('io_uring_queue_init_params: Operation not permitted').
+        # Without liburing-dev the CMake probe disables the backend and
+        # the cmake-mainproject/subdirectory jobs exercise epoll only.
+        # io_uring runtime coverage is provided by the GitHub Actions
+        # Linux jobs, which run on unrestricted GitHub-hosted runners.
+        linux_cxx("cmake-mainproject", "g++-13", packages="g++-13",
+            image="cppalliance/droneubuntu2404:1",
+            buildtype="cmake-mainproject", buildscript="drone",
+            environment={
+                'COMMENT': 'cmake-mainproject',
+                'CXX': 'g++-13',
+            },
+            globalenv=globalenv),
+
+        linux_cxx("cmake-subdirectory", "g++-13", packages="g++-13",
+            image="cppalliance/droneubuntu2404:1",
+            buildtype="cmake-subdirectory", buildscript="drone",
+            environment={
+                'COMMENT': 'cmake-subdirectory',
+                'CXX': 'g++-13',
+            },
+            globalenv=globalenv)
+
+        # windows_cxx("msvc-14.3 cmake-superproject", "",
+        #     image="cppalliance/dronevs2022:1",
+        #     buildtype="cmake-superproject", buildscript="drone",
+        #     environment={
+        #         'B2_TOOLSET': 'msvc-14.3',
+        #         'B2_CXXSTD': '20',
+        #     },
+        #     globalenv=globalenv),
+    ]
+
+    return jobs
+
 
 # from https://github.com/cppalliance/ci-automation
 load("@ci_automation//ci/drone/:functions.star", "linux_cxx", "windows_cxx", "osx_cxx", "freebsd_cxx", "generate")

.drone/drone.bat

@@ -47,6 +47,9 @@ pushd !BOOST_ROOT!\libs
 git clone https://github.com/cppalliance/capy -b !BOOST_BRANCH! --depth 1
 popd
 pushd !BOOST_ROOT!\libs
+git clone https://github.com/cppalliance/corosio -b !BOOST_BRANCH! --depth 1
+popd
+pushd !BOOST_ROOT!\libs
 git clone https://github.com/cppalliance/http -b !BOOST_BRANCH! --depth 1
 popd
 

.drone/drone.sh

@@ -47,6 +47,12 @@ common_install () {
     popd
   fi
 
+  if [ ! -d "$BOOST_ROOT/libs/corosio" ]; then
+    pushd $BOOST_ROOT/libs
+    git clone https://github.com/cppalliance/corosio -b $BOOST_BRANCH --depth 1
+    popd
+  fi
+
   if [ ! -d "$BOOST_ROOT/libs/http" ]; then
     pushd $BOOST_ROOT/libs
     git clone https://github.com/cppalliance/http -b $BOOST_BRANCH --depth 1
@@ -139,6 +145,12 @@ if [ ! -d "$BOOST_ROOT/libs/capy" ]; then
   popd
 fi
 
+if [ ! -d "$BOOST_ROOT/libs/corosio" ]; then
+  pushd $BOOST_ROOT/libs
+  git clone https://github.com/cppalliance/corosio -b $BOOST_BRANCH --depth 1
+  popd
+fi
+
 if [ ! -d "$BOOST_ROOT/libs/http" ]; then
   pushd $BOOST_ROOT/libs
   git clone https://github.com/cppalliance/http -b $BOOST_BRANCH --depth 1