Experiment: Look for libstdc++ packages in debian:testing

.github/workflows/linux.yaml

@@ -26,11 +26,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # !!!!!!!!
-        os: [ 'debian:testing' ]
-        compiler: [ 'clang' ]
-        sanitizer: [ 'none' ] # ThreadSanitizer reports errors
-        tls: [ 'true' ]
+        os: [ 'debian:stable', 'debian:testing', 'registry.access.redhat.com/ubi8/ubi-minimal', 'registry.access.redhat.com/ubi9/ubi-minimal' ]
+        compiler: [ 'gcc', 'clang' ]
+        sanitizer: [ 'address', 'undefined', 'none' ] # ThreadSanitizer reports errors
+        tls: [ 'true', 'false' ]
         exclude:
           - os: 'registry.access.redhat.com/ubi8/ubi-minimal'
             sanitizer: 'address'
@@ -58,10 +57,24 @@ jobs:
       if: contains(matrix.os, 'debian')
       run: |
         if [ ${{ matrix.compiler }} = gcc ]; then compiler=g++; else compiler="clang lld ?exact-name(libclang-rt-dev)"; fi
-        # apt -y update # !!!!!!!!
+        apt -y update
         apt -y install $compiler meson pkg-config cmake rapidjson-dev libssl-dev netbase '?exact-name(libhowardhinnant-date-dev)' '?exact-name(libgmock-dev) (?version([1-9]\.[1-9][1-9]) | ?version([1-9]\.[2-9][0-9]))' '?exact-name(libcpp-httplib-dev)' libcurl4-openssl-dev git ca-certificates curl gpg gpgv gpg-agent lcov llvm-dev --no-install-recommends
 
-        # if [ ${{ matrix.compiler }} = clang ] && [ ${{ matrix.os == 'debian:testing' }} ]; then libstdcpp_latest=$(apt-cache search "libstdc++" | grep "libstdc++-..-dev " | sort -r | head -c 16); libstdcpp_latest_fst9=$(echo "${libstdcpp_latest}" | head -c 9); libstdcpp_latest_lst3=$(echo "${libstdcpp_latest}" | tail -c 4 | head -c 3); if [ ${libstdcpp_latest_fst9} = "libstdc++" ]  && [ ${libstdcpp_latest_lst3} = "dev" ]; then apt -y install ${libstdcpp_latest} --no-install-recommends; fi; fi
+        # Periodically, debian:testing fails with clang, saying that
+        # libstdc++ cannot be found. In debian:testing/clang, normally
+        # libstdc++-dev is installed as a dependency of meson. In the
+        # situation where the build breaks, the meson dependency is
+        # different to the latest available libstdc++; for instance,
+        # installing meson dependencies might install
+        # libstdc++-13-dev, whereas apt has access to
+        # libstdc++-14-dev. In other situations, the meson dependency
+        # libstdc++-..-dev may be the same as the latest
+        # libstdc++-..-dev to which apt has access.
+        #
+        # To prevent the build breaking, we need to install the latest
+        # libstdc++-..-dev to which apt has access - not the N-1
+        # version which may be installed as a meson dependency.
+        if [ ${{ matrix.compiler }} = clang ] && [ ${{ matrix.os == 'debian:testing' }} ]; then libstdcpp_latest=$(apt-cache search "libstdc++" | grep "libstdc++-..-dev " | sort -r | head -c 16); libstdcpp_latest_fst9=$(echo "${libstdcpp_latest}" | head -c 9); libstdcpp_latest_lst3=$(echo "${libstdcpp_latest}" | tail -c 4 | head -c 3); if [ ${libstdcpp_latest_fst9} = "libstdc++" ]  && [ ${libstdcpp_latest_lst3} = "dev" ]; then apt -y install ${libstdcpp_latest} --no-install-recommends; fi; fi
 
     - name: Install dependencies (Red Hat)
       if: contains(matrix.os, 'redhat')