Add gcc and g++ to the Debian and Ubuntu clang images

docker/debian/Dockerfile

@@ -81,9 +81,12 @@ ldconfig -v
 dpkg-divert --divert /usr/bin/gcc.orig --rename /usr/bin/gcc
 dpkg-divert --divert /usr/bin/g++.orig --rename /usr/bin/g++
 dpkg-divert --divert /usr/bin/gfortran.orig --rename /usr/bin/gfortran
-update-alternatives --install /usr/bin/cc cc /usr/local/bin/gcc 999
-update-alternatives --install \
-  /usr/bin/gcc gcc /usr/local/bin/gcc 100 \
+update-alternatives \
+  --install /usr/bin/cc cc /usr/local/bin/gcc 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /usr/local/bin/g++ 999
+update-alternatives \
+  --install /usr/bin/gcc gcc /usr/local/bin/gcc 100 \
   --slave /usr/bin/g++ g++ /usr/local/bin/g++ \
   --slave /usr/bin/gcc-ar gcc-ar /usr/local/bin/gcc-ar \
   --slave /usr/bin/gcc-nm gcc-nm /usr/local/bin/gcc-nm \
@@ -93,6 +96,7 @@ update-alternatives --install \
   --slave /usr/bin/gcov-dump gcov-dump /usr/local/bin/gcov-dump \
   --slave /usr/bin/lto-dump lto-dump /usr/local/bin/lto-dump
 update-alternatives --auto cc
+update-alternatives --auto c++
 update-alternatives --auto gcc
 EOF
 # Set the compiler environment variables to point to the GCC binaries.
@@ -144,7 +148,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh gcc
 cd ..
 rm -rf test
 EOF
@@ -157,10 +161,12 @@ ARG DEBIAN_FRONTEND=noninteractive
 
 # Install Clang. Use the LLVM apt repository to access the latest versions. We
 # must repeat the DEBIAN_VERSION argument here, as it is not inherited from the
-# base or source images.
+# base or source images. Some build dependencies require GCC to be also available.
 ARG DEBIAN_VERSION
 ARG CLANG_VERSION
 RUN <<EOF
+apt-get update
+apt-get install -y --no-install-recommends gcc g++
 curl --no-progress-meter https://apt.llvm.org/llvm-snapshot.gpg.key | gpg --dearmor -o /etc/apt/keyrings/llvm.gpg
 printf "%s\n%s\n" \
   "deb [signed-by=/etc/apt/keyrings/llvm.gpg] https://apt.llvm.org/${DEBIAN_VERSION}/ llvm-toolchain-${DEBIAN_VERSION}-${CLANG_VERSION} main" \
@@ -169,13 +175,17 @@ apt-get update
 apt-get install -t llvm-toolchain-${DEBIAN_VERSION}-${CLANG_VERSION} -y --no-install-recommends clang-${CLANG_VERSION} llvm-${CLANG_VERSION}
 apt-get clean
 rm -rf /var/lib/apt/lists/*
-update-alternatives --install /usr/bin/cc cc /usr/bin/clang-${CLANG_VERSION} 999
-update-alternatives --install \
-    /usr/bin/clang clang /usr/bin/clang-${CLANG_VERSION} 100 \
-    --slave /usr/bin/clang++ clang++ /usr/bin/clang++-${CLANG_VERSION}
-update-alternatives --install \
-    /usr/bin/llvm-cov llvm-cov /usr/bin/llvm-cov-${CLANG_VERSION} 100
+update-alternatives \
+  --install /usr/bin/cc cc /usr/bin/clang-${CLANG_VERSION} 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /usr/bin/clang++-${CLANG_VERSION} 999
+update-alternatives \
+  --install /usr/bin/clang clang /usr/bin/clang-${CLANG_VERSION} 100 \
+  --slave /usr/bin/clang++ clang++ /usr/bin/clang++-${CLANG_VERSION}
+update-alternatives \
+  --install /usr/bin/llvm-cov llvm-cov /usr/bin/llvm-cov-${CLANG_VERSION} 100
 update-alternatives --auto cc
+update-alternatives --auto c++
 update-alternatives --auto clang
 update-alternatives --auto llvm-cov
 EOF
@@ -225,7 +235,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh clang
 cd ..
 rm -rf test
 EOF

docker/rhel/Dockerfile

@@ -53,15 +53,19 @@ dnf remove -y gcc gcc-c++
 dnf install -y --setopt=tsflags=nodocs gcc-toolset-${GCC_VERSION}-gcc gcc-toolset-${GCC_VERSION}-gcc-c++
 dnf clean -y all
 rm -rf /var/cache/dnf/*
-update-alternatives --install /usr/bin/cc cc /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcc 999
 update-alternatives \
-    --install /usr/bin/gcc gcc /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcc 100 \
-    --slave /usr/bin/g++ g++ /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/g++ \
-    --slave /usr/bin/cpp cpp /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/cpp \
-    --slave /usr/bin/gcov gcov /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov \
-    --slave /usr/bin/gcov-dump gcov-dump /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov-dump-${GCC_VERSION} \
-    --slave /usr/bin/gcov-tool gcov-tool /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov-tool-${GCC_VERSION}
+  --install /usr/bin/cc cc /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcc 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/g++ 999
+update-alternatives \
+  --install /usr/bin/gcc gcc /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcc 100 \
+  --slave /usr/bin/g++ g++ /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/g++ \
+  --slave /usr/bin/cpp cpp /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/cpp \
+  --slave /usr/bin/gcov gcov /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov \
+  --slave /usr/bin/gcov-dump gcov-dump /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov-dump-${GCC_VERSION} \
+  --slave /usr/bin/gcov-tool gcov-tool /opt/rh/gcc-toolset-${GCC_VERSION}/root/usr/bin/gcov-tool-${GCC_VERSION}
 update-alternatives --auto cc
+update-alternatives --auto c++
 update-alternatives --auto gcc
 EOF
 # Set the compiler environment variables to point to the GCC binaries.
@@ -110,7 +114,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh gcc
 cd ..
 rm -rf test
 EOF
@@ -119,13 +123,18 @@ EOF
 FROM base AS clang
 
 # Install Clang. Note that in the RHEL UBIs, we cannot choose the Clang version
-# to install and we get what is available.
+# to install and we get what is available. Some build dependencies require GCC
+# to be also available.
 RUN <<EOF
-dnf install -y --setopt=tsflags=nodocs clang llvm
+dnf install -y --setopt=tsflags=nodocs clang llvm gcc gcc-c++
 dnf clean -y all
 rm -rf /var/cache/dnf/*
-update-alternatives --install /usr/bin/cc cc /usr/bin/clang 999
+update-alternatives \
+  --install /usr/bin/cc cc /usr/bin/clang 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /usr/bin/clang++ 999
 update-alternatives --auto cc
+update-alternatives --auto c++
 EOF
 # Set the compiler environment variables to point to the GCC binaries.
 ENV CC=/usr/bin/clang
@@ -174,7 +183,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh clang
 cd ..
 rm -rf test
 EOF

docker/ubuntu/Dockerfile

@@ -67,19 +67,23 @@ ARG GCC_VERSION
 RUN <<EOF
 apt-get update
 apt-get install -y --no-install-recommends \
-    gcc-${GCC_VERSION} \
-    g++-${GCC_VERSION} \
-    debhelper
+  gcc-${GCC_VERSION} \
+  g++-${GCC_VERSION} \
+  debhelper
 apt-get clean
 rm -rf /var/lib/apt/lists/*
-update-alternatives --install /usr/bin/cc cc /usr/bin/gcc-${GCC_VERSION} 999
 update-alternatives \
-    --install /usr/bin/gcc gcc /usr/bin/gcc-${GCC_VERSION} 100 \
-    --slave /usr/bin/g++ g++ /usr/bin/g++-${GCC_VERSION} \
-    --slave /usr/bin/gcov gcov /usr/bin/gcov-${GCC_VERSION} \
-    --slave /usr/bin/gcov-dump gcov-dump /usr/bin/gcov-dump-${GCC_VERSION} \
-    --slave /usr/bin/gcov-tool gcov-tool /usr/bin/gcov-tool-${GCC_VERSION}
+  --install /usr/bin/cc cc /usr/bin/gcc-${GCC_VERSION} 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /usr/bin/g++-${GCC_VERSION} 999
+update-alternatives \
+  --install /usr/bin/gcc gcc /usr/bin/gcc-${GCC_VERSION} 100 \
+  --slave /usr/bin/g++ g++ /usr/bin/g++-${GCC_VERSION} \
+  --slave /usr/bin/gcov gcov /usr/bin/gcov-${GCC_VERSION} \
+  --slave /usr/bin/gcov-dump gcov-dump /usr/bin/gcov-dump-${GCC_VERSION} \
+  --slave /usr/bin/gcov-tool gcov-tool /usr/bin/gcov-tool-${GCC_VERSION}
 update-alternatives --auto cc
+update-alternatives --auto c++
 update-alternatives --auto gcc
 EOF
 # Set the compiler environment variables to point to the GCC binaries.
@@ -128,7 +132,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh gcc
 cd ..
 rm -rf test
 EOF
@@ -139,22 +143,28 @@ FROM base AS clang
 # This is not inherited from base image, ensure no manual interaction needed.
 ARG DEBIAN_FRONTEND=noninteractive
 
-# Install Clang.
+# Install Clang. Some build dependencies require GCC to be also available.
 ARG CLANG_VERSION
 RUN <<EOF
 apt-get update
 apt-get install -y --no-install-recommends \
-    clang-${CLANG_VERSION} \
-    llvm-${CLANG_VERSION}
+  clang-${CLANG_VERSION} \
+  llvm-${CLANG_VERSION} \
+  gcc \
+  g++
 apt-get clean
 rm -rf /var/lib/apt/lists/*
-update-alternatives --install /usr/bin/cc cc /usr/bin/clang-${CLANG_VERSION} 999
-update-alternatives --install \
-    /usr/bin/clang clang /usr/bin/clang-${CLANG_VERSION} 100 \
-    --slave /usr/bin/clang++ clang++ /usr/bin/clang++-${CLANG_VERSION}
-update-alternatives --install \
-    /usr/bin/llvm-cov llvm-cov /usr/bin/llvm-cov-${CLANG_VERSION} 100
+update-alternatives \
+  --install /usr/bin/cc cc /usr/bin/clang-${CLANG_VERSION} 999
+update-alternatives \
+  --install /usr/bin/c++ c++ /usr/bin/clang++-${CLANG_VERSION} 999
+update-alternatives \
+  --install /usr/bin/clang clang /usr/bin/clang-${CLANG_VERSION} 100 \
+  --slave /usr/bin/clang++ clang++ /usr/bin/clang++-${CLANG_VERSION}
+update-alternatives \
+  --install /usr/bin/llvm-cov llvm-cov /usr/bin/llvm-cov-${CLANG_VERSION} 100
 update-alternatives --auto cc
+update-alternatives --auto c++
 update-alternatives --auto clang
 update-alternatives --auto llvm-cov
 EOF
@@ -204,7 +214,7 @@ RUN conan profile show
 # Test the image by compiling a simple C++ program.
 RUN --mount=type=bind,source=test,target=/test,readonly <<EOF
 cp -r /test test
-cd test && ./run.sh
+cd test && ./run.sh clang
 cd ..
 rm -rf test
 EOF

test/run.sh

@@ -1,6 +1,7 @@
 #!/bin/bash
 
 set -ex
+set -o pipefail
 
 # Install Conan dependencies, configure the project, and build the executable.
 conan install . --output-folder=build --build=missing
@@ -9,7 +10,7 @@ cmake .. -DCMAKE_TOOLCHAIN_FILE=conan_toolchain.cmake -DCMAKE_BUILD_TYPE=Release
 cmake --build .
 
 # Run the executable.
-./example
+./example | grep -E "^Compiler used: $1$"
 
 # Remove the Conan dependencies.
 conan remove -c "*"

test/src/main.cpp

@@ -30,5 +30,14 @@ int main(void) {
 
     std::printf("ZLIB VERSION: %s\n", zlibVersion());
 
+#ifdef __clang__
+    constexpr char which[] = "clang";
+#elif __GNUC__
+    constexpr char which[] = "gcc";
+#else
+    constexpr char which[] = "unknown";
+#endif
+    std::printf("Compiler used: %s\n", which);
+
     return EXIT_SUCCESS;
 }