build Windows debug client/server with ASAN

This commit updates the `tests/CMakeLists.txt` configuration for
building the client/server examples on Windows to enable address
sanitizer (ASAN). We were already doing this for Linux and MacOS builds
but were missing Windows coverage.

Notably this requires a modern MSVC configured on the $PATH at runtime
so that the ASAN DLLs are present. Otherwise the built binaries
cryptically exit immediately with no output, just the exit status
-1073741515. We use the setup-msvc-dev action in CI to do this for us.

See the Microsoft documentation for more information:
https://devblogs.microsoft.com/cppblog/addresssanitizer-asan-for-windows-with-msvc/#compiling-with-asan-from-the-console

Author: cpu

.github/workflows/test.yaml

@@ -111,6 +111,14 @@ jobs:
           persist-credentials: false
       - name: Install nightly rust toolchain
         uses: dtolnay/rust-toolchain@nightly
+      # For Debug builds we use ASAN, which requires a modern MSVC on $PATH
+      # to provide the ASAN clang_rt.asan_*.dll runtime deps or
+      # the built client/server binary will exit immediately with 
+      # exit code -1073741515
+      - name: Setup MSVC
+        uses: TheMrMilchmann/setup-msvc-dev@v3
+        with:
+          arch: x64
       - name: Configure CMake
         run: cmake -DCRYPTO_PROVIDER="${{ matrix.crypto }}" -S . -B build
       - name: Build, debug configuration

tests/CMakeLists.txt

@@ -13,6 +13,10 @@ elseif (CRYPTO_PROVIDER STREQUAL "ring")
     add_compile_definitions(DEFINE_RING)
 endif ()
 
+# Set ASAN sanitizer flags conditionally for Debug builds
+set(sanitizer_flags "$<$<CONFIG:Debug>:-fsanitize=address>")
+add_compile_options(${sanitizer_flags})
+
 add_executable(client client.c common.c)
 add_dependencies(client rustls-ffi)
 target_include_directories(client PUBLIC ${CMAKE_SOURCE_DIR}/src)