Ensure all IO errors are exhaustively handled

.github/workflows/ci.yml

@@ -56,3 +56,21 @@ jobs:
       - name: Build Redis macOS
         run: make CC="zig cc -target x86_64-macos" CXX="zig c++ -target x86_64-macos" AR="${GITHUB_WORKSPACE}/zig-out/bin/zar" RANLIB="zig ranlib" uname_S="Darwin" uname_M="x86_64" USE_JEMALLOC=no USE_SYSTEMD=no
         working-directory: redis
+  test_io_errors_handled:
+    name: Test handled errors are actually handled
+    timeout-minutes: 15
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+        with:
+          submodules: recursive
+      - name: Setup Zig
+        uses: goto-bus-stop/setup-zig@v1
+        with:
+          version: master
+      - name: Build
+        run: zig build -Dtest-errors-handled=true

build.zig

@@ -30,6 +30,9 @@ pub fn build(b: *std.build.Builder) void {
     tests.addOptions("build_options", exe_options);
     tests_exe.addOptions("build_options", exe_options);
 
+    const test_errors_handled = b.option(bool, "test-errors-handled", "Compile with this to confirm zar sends all io errors through the io error handler") orelse false;
+    exe_options.addOption(bool, "test_errors_handled", test_errors_handled);
+
     {
         const tracy = b.option([]const u8, "tracy", "Enable Tracy integration. Supply path to Tracy source");
         const tracy_callstack = b.option(bool, "tracy-callstack", "Include callstack information with Tracy data. Does nothing if -Dtracy is not provided") orelse false;