Explicit images

Author: gummif

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: ["ubuntu-latest"]
+        os: ["ubuntu-20.04"]
         cppstd: ["98", "11", "20"]
         cc: ["gcc-10"]
         cxx: ["g++-10"]
@@ -20,23 +20,23 @@ jobs:
         libzmqbuild: ["cmake"]
         include:
           # older libzmq and without draft
-          - os: "ubuntu-22.04"
+          - os: "ubuntu-20.04"
             cppstd: "11"
-            cc: "gcc-11"
-            cxx: "g++-11"
+            cc: "gcc-9"
+            cxx: "g++-9"
             drafts: "OFF"
             libzmq: "4.2.0"
             libzmqbuild: "pkgconfig"
           # without draft
-          - os: "ubuntu-latest"
+          - os: "ubuntu-22.04"
             cppstd: "20"
-            cc: "gcc-10"
-            cxx: "g++-10"
+            cc: "gcc-11"
+            cxx: "g++-11"
             drafts: "OFF"
             libzmq: "4.3.4"
             libzmqbuild: "cmake"
           # coverage (gcc version should match gcov version)
-          - os: "ubuntu-latest"
+          - os: "ubuntu-20.04"
             cppstd: "17"
             cc: "gcc-9"
             cxx: "g++-9"
@@ -46,7 +46,7 @@ jobs:
             coverage: "-DCOVERAGE=ON"
             aptinstall: "lcov"
           # clang
-          - os: "ubuntu-latest"
+          - os: "ubuntu-20.04"
             cppstd: "17"
             cc: "clang-12"
             cxx: "clang++-12"
@@ -71,7 +71,7 @@ jobs:
             libzmq: "4.3.4"
             libzmqbuild: "cmake"
             platform: "-Ax64"
-          - os: "windows-latest"
+          - os: "windows-2022"
             cppstd: "20"
             cc: "msbuild"
             cxx: "msbuild"