Add failing test for cmake-modules + cmake 4 version

Author: Felixoid

tests/integration/Makefile

@@ -23,7 +23,7 @@ export SCCACHE_PATH := /sccache/target/debug/sccache
 endif
 
 BACKENDS := redis redis-deprecated memcached memcached-deprecated s3 azblob webdav basedirs
-TOOLS := gcc clang cmake cmake-modules autotools coverage zstd
+TOOLS := gcc clang cmake cmake-modules cmake-modules-v4 autotools coverage zstd
 
 # Map backends to their compose profiles
 PROFILES_autotools := autotools
@@ -32,6 +32,7 @@ PROFILES_basedirs := basedirs redis memcached s3 azblob webdav
 PROFILES_clang := clang
 PROFILES_cmake := cmake
 PROFILES_cmake-modules := cmake-modules
+PROFILES_cmake-modules-v4 := cmake-modules-v4
 PROFILES_coverage := coverage
 PROFILES_gcc := gcc
 PROFILES_memcached := memcached
@@ -49,6 +50,7 @@ SERVICES_basedirs := redis memcached minio minio-setup azurite azurite-setup web
 SERVICES_clang :=
 SERVICES_cmake :=
 SERVICES_cmake-modules :=
+SERVICES_cmake-modules-v4 :=
 SERVICES_coverage :=
 SERVICES_gcc :=
 SERVICES_memcached := memcached
@@ -81,6 +83,7 @@ help:
 	@echo "Build System Tests:"
 	@echo "  make test-cmake              Run CMake integration test"
 	@echo "  make test-cmake-modules      Run CMake C++20 modules test"
+	@echo "  make test-cmake-modules-v4   Run CMake 4.x C++20 modules test (xfail)"
 	@echo "  make test-autotools          Run Autotools integration test"
 	@echo ""
 	@echo "Advanced Tests:"

tests/integration/cmake-modules-v4.Dockerfile

@@ -0,0 +1,4 @@
+FROM silkeh/clang:21-trixie
+RUN apt-get update -qq && apt-get install -y -qq ninja-build python3 python3-pip \
+    && pip install --break-system-packages cmake \
+    && rm -rf /var/lib/apt/lists/*

tests/integration/docker-compose.yml

@@ -285,6 +285,19 @@ services:
       - test
       - cmake-modules
 
+  test-cmake-modules-v4:
+    <<: *test-runner
+    build:
+      context: .
+      dockerfile: cmake-modules-v4.Dockerfile
+    entrypoint: /sccache/tests/integration/scripts/test-cmake-modules-v4.sh
+    environment:
+      <<: *common-env
+      SCCACHE_DIR: /build/sccache
+    profiles:
+      - test
+      - cmake-modules-v4
+
   test-autotools:
     <<: *test-runner
     image: gcc:latest

tests/integration/scripts/test-cmake-modules-v4.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+set -euo pipefail
+
+# XFAIL: cmake 4.x generates arguments that trigger sccache's @ response file
+# rejection in gcc.rs:349. This test tracks the issue and captures the actual
+# compiler commands for debugging.
+
+SCCACHE="${SCCACHE_PATH:-/sccache/target/debug/sccache}"
+
+echo "=========================================="
+echo "Testing: CMake 4.x C++20 Modules (XFAIL)"
+echo "=========================================="
+
+echo "cmake version: $(cmake --version | head -1)"
+echo "clang version: $(clang++ --version | head -1)"
+
+# Copy cmake-modules project to writable location
+cp -r /sccache/tests/integration/cmake-modules /build/cmake-modules
+
+# Start sccache server
+"$SCCACHE" --start-server || true
+
+echo ""
+echo "Build 1: Capture compiler commands"
+cd /build/cmake-modules
+cmake -B build -G Ninja \
+    -DCMAKE_C_COMPILER=clang \
+    -DCMAKE_CXX_COMPILER=clang++ \
+    -DCMAKE_C_COMPILER_LAUNCHER="$SCCACHE" \
+    -DCMAKE_CXX_COMPILER_LAUNCHER="$SCCACHE"
+
+echo ""
+echo "=== Ninja build rules (grep for @ in commands) ==="
+grep '@' build/build.ninja || echo "(no @ found in build.ninja)"
+
+echo ""
+echo "=== Full compiler commands (ninja -v) ==="
+cmake --build build -- -v 2>&1 | cat
+
+echo ""
+echo "=== sccache stats ==="
+"$SCCACHE" --show-stats
+
+STATS_JSON=$("$SCCACHE" --show-stats --stats-format=json)
+NOT_CACHED=$(echo "$STATS_JSON" | python3 -c "import sys, json; print(json.load(sys.stdin).get('stats', {}).get('not_cached', {}).get('@', 0))")
+CACHE_HITS=$(echo "$STATS_JSON" | python3 -c "import sys, json; stats = json.load(sys.stdin).get('stats', {}); print(stats.get('cache_hits', {}).get('counts', {}).get('C/C++', 0))")
+
+echo ""
+echo "Cache hits: $CACHE_HITS"
+echo "Non-cacheable @: $NOT_CACHED"
+
+if [ "$CACHE_HITS" -gt 0 ]; then
+    echo "XPASS: CMake 4.x C++20 modules now cacheable! Remove XFAIL status."
+    exit 1
+fi
+
+if [ "$NOT_CACHED" -gt 0 ]; then
+    echo "XFAIL: cmake 4.x @ issue reproduced (expected failure)"
+    exit 0
+fi
+
+echo "FAIL: Unexpected failure"
+echo "$STATS_JSON" | python3 -m json.tool
+exit 1