Use CMake 4.5's stable import std support in the module test (#6103)

* Use CMake 4.5's stable import std support in the module test

CMake 4.5 makes `import std` available to every target that scans for
C++ modules and drops the experimental CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
gate and the CXX_MODULE_STD property. The module test no longer needs the
version-specific opt-in token, so the ci_module_cpp20 jobs no longer have
to pin CMake 4.3.4 and now request CMake ^4.5.0.

The modules, CMake and README documentation now list the CMake, generator
and toolchain requirements for building the module and for `import std;`.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Bump lukka/get-cmake from 4.4.5 to 4.5.0

get-cmake 4.4.5 does not know CMake 4.5.0, so the ci_module_cpp20 jobs
that request '^4.5.0' failed in the setup step. Bump every pin so all
jobs use the same action version.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Install unzip in the Clang module job before get-cmake

The ^4.5.0 CMake/Ninja cache key is new, so get-cmake has to unzip the
Ninja download, and silkeh/clang:latest has no unzip.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Disable C++ module scanning for the unit tests

With CMake 4.5, every target that scans for C++ modules gets a synthesized
std module target. For the C++20 and newer unit-test targets, this compiled
libstdc++'s std.cc with the -Werror test flags and failed to configure with
libc++ images that lack std.compat.cppm. The unit tests use no modules, so
turn scanning off; the module test is a separate project.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann authored and GitHub committed 2026-11-15 17:02:52 +01:00
1 parent 99adff001d
commit 7127a82fa1
8 files changed
+62 -44

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+26 -23
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@@ -25,7 +25,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -38,7 +38,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Check that Meson and pkg-config offer the CMake options
run: make check_build_options
- name: Install Meson
@@ -92,7 +92,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -123,7 +123,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -142,7 +142,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -168,7 +168,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -244,7 +244,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: CXX=g++-${{ matrix.compiler }} cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -262,7 +262,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -279,7 +279,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Disable filesystem support (std::filesystem is unusable) for clang 7 / 8 / 9 / 10
run: echo "JSON_FORCED_GLOBAL_COMPILE_OPTIONS=-DJSON_HAS_FILESYSTEM=0;-DJSON_HAS_EXPERIMENTAL_FILESYSTEM=0" >> "$GITHUB_ENV"
if: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
@@ -299,7 +299,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -319,7 +319,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build with libc++
@@ -346,7 +346,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -362,13 +362,16 @@ jobs:
- uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
with:
persist-credentials: false
# The module test uses `import std;`, which needs CMake's experimental
# import-std support. Its opt-in token is CMake-version-specific, so pin
# CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
- name: Get pinned CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
# get-cmake extracts the Ninja zip with the system unzip, which the Clang
# image lacks; other Clang jobs get away with it by hitting the cache.
- name: Install unzip (Clang)
if: matrix.container == 'silkeh/clang:latest'
run: apt-get update ; apt-get install -y unzip
# The module test uses `import std;`, which needs CMake 4.5 or newer.
- name: Get CMake 4.5+ and ninja
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
with:
cmakeVersion: 4.3.4
cmakeVersion: '^4.5.0'
# Clang: the std library module is provided by libc++ (the image's libstdc++
# ships none), and the image's libc++ module manifest has a broken relative
# path — repoint it at the real module sources.
@@ -392,7 +395,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -409,7 +412,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -423,7 +426,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DJSON_CI=On
- name: Build
@@ -443,7 +446,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Run CMake
run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -GNinja
- name: Build
@@ -484,7 +487,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Check that the job runs natively on arm64
run: uname -m && test "$(uname -m)" = aarch64
- name: Run CMake
+5 -7
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@@ -90,7 +90,7 @@ jobs:
with:
persist-credentials: false
- name: Get latest CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
- name: Set extra CXX_FLAGS for latest std_version
# /wd5285 silences C5285 emitted by the bundled third-party doctest.h, which
# specializes std::tuple (newly diagnosed by the VS2026 v145 toolset)
@@ -212,13 +212,11 @@ jobs:
- uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
with:
persist-credentials: false
# The module test uses `import std;`, which needs CMake's experimental
# import-std support. Its opt-in token is CMake-version-specific, so pin
# CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
- name: Get pinned CMake and ninja
uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
# The module test uses `import std;`, which needs CMake 4.5 or newer.
- name: Get CMake 4.5+ and ninja
uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
with:
cmakeVersion: 4.3.4
cmakeVersion: '^4.5.0'
# CMAKE_CXX_FLAGS replaces CMake's MSVC defaults (which include /EHsc), and
# ci_module_cpp20 forwards it to the module build, so list /EHsc explicitly
- name: Run CMake (Debug)