diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..610ab56
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,47 @@
+on:
+  - push
+
+jobs:
+  build-linux:
+    name: Use clang and gcc via "Unix Makefiles"
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: [clang, gcc]
+    steps:
+      - uses: actions/checkout@v4
+      - run: |
+          cmake -Bbuild -DCMAKE_C_COMPILER=${{ matrix.compiler }}
+          cmake --build build
+
+  build-windows-ninja:
+    name: Use clang and clang-cl via Ninja
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        # On Windows, clang only enables the WIN32 flag in CMake whereas
+        # clang-cl also enables MSVC, because it has a cl.exe-like interface.
+        compiler: [clang, clang-cl]
+    steps:
+      - uses: actions/checkout@v4
+      - run: |
+          # Use Ninja because the MSBuild toolchain can only configure
+          # alternative compilers via "toolsets", where only ClangCL is
+          # supported.
+          cmake -Bbuild -GNinja -DCMAKE_C_COMPILER=${{ matrix.compiler }}
+          cmake --build build
+
+  build-windows-msbuild:
+    name: Use MSVC and clang-cl via MSBuild
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        toolset:
+          # The default toolset should be the latest 'v143' when nothing is specified
+          -
+          - -TClangCL
+    steps:
+      - uses: actions/checkout@v4
+      - run: |
+          cmake -Bbuild ${{ matrix.toolset }}
+          cmake --build build
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6a9a694..b2ae9e4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,7 +73,7 @@ target_include_directories(${PROJECT_NAME}
          $<INSTALL_INTERFACE:include>)
 
 target_link_libraries(${PROJECT_NAME}
-  PUBLIC $<$<NOT:$<C_COMPILER_ID:MSVC>>:m>)
+  PUBLIC $<$<NOT:$<BOOL:${WIN32}>>:m>)
 
 set_target_properties(${PROJECT_NAME} PROPERTIES
   SOVERSION ${PROJECT_VERSION_MAJOR}
diff --git a/Makefile b/Makefile
index c43a479..e14b66a 100644
--- a/Makefile
+++ b/Makefile
@@ -72,12 +72,11 @@ ifneq ($(shared), not-set)
 endif
 
 define run-config
-mkdir -p $(BUILDDIR)
-cd $(BUILDDIR) && cmake $(CURDIR) $(CONFIG_FLAGS)
+cmake $(CURDIR) -B"$(BUILDDIR)" $(CONFIG_FLAGS)
 endef
 
 all clean install: $(BUILDDIR)
-	make -C $(BUILDDIR) $@
+	cmake --build $(BUILDDIR) $@
 
 uninstall:
 	 xargs rm < $(BUILDDIR)/install_manifest.txt
diff --git a/cmake/GKlibSystem.cmake b/cmake/GKlibSystem.cmake
deleted file mode 100644
index 249d424..0000000
--- a/cmake/GKlibSystem.cmake
+++ /dev/null
@@ -1,51 +0,0 @@
-# Helper modules.
-
-# Add compiler flags.
-if(MSVC)
-  set(GKlib_COPTS "/Ox")
-  set(GKlib_COPTIONS "-DWIN32 -DMSC -D_CRT_SECURE_NO_DEPRECATE -DUSE_GKREGEX")
-elseif(MINGW)
-  set(GKlib_COPTS "-DUSE_GKREGEX")
-else()
-  set(GKlib_COPTIONS "-DLINUX -D_FILE_OFFSET_BITS=64")
-endif(MSVC)
-
-if(CYGWIN)
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -DCYGWIN")
-endif(CYGWIN)
-
-if(CMAKE_C_COMPILER_ID MATCHES "GNU|Clang")
-# GCC opts.
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -std=c99 -fno-strict-aliasing")
-
-  if(VALGRIND)
-    set(GKlib_COPTIONS "${GK_COPTIONS} -march=x86-64 -mtune=generic")
-  else()
-    set(GKlib_COPTIONS "${GKlib_COPTIONS} -march=native")
-  endif(VALGRIND)
-
-  if(NOT MINGW)
-      set(GKlib_COPTIONS "${GKlib_COPTIONS} -fPIC")
-  endif(NOT MINGW)
-
-# GCC warnings.
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -Werror -Wall -pedantic -Wno-unused-function -Wno-unused-but-set-variable -Wno-unused-variable -Wno-unknown-pragmas -Wno-unused-label")
-endif()
-
-if(${CMAKE_C_COMPILER_ID} MATCHES "Sun")
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -xc99")
-endif()
-
-# Intel compiler
-if(${CMAKE_C_COMPILER_ID} MATCHES "Intel")
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -xHost -std=c99")
-endif()
-
-# Set the CPU type 
-if(NO_X86)
-  set(GKlib_COPTIONS "${GKlib_COPTIONS} -DNO_X86=${NO_X86}")
-endif(NO_X86)
-
-
-# Finally set the official C flags.
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GKlib_COPTIONS} ${GKlib_COPTS}")
diff --git a/include/gk_arch.h b/include/gk_arch.h
index b82fb6a..b05192a 100644
--- a/include/gk_arch.h
+++ b/include/gk_arch.h
@@ -53,7 +53,7 @@
 /*************************************************************************
 * Architecture-specific modifications
 **************************************************************************/
-#ifdef WIN32
+#ifdef _WIN32
 typedef ptrdiff_t ssize_t;
 #endif
 
diff --git a/src/error.c b/src/error.c
index e2a18cf..bf7ac72 100644
--- a/src/error.c
+++ b/src/error.c
@@ -174,7 +174,7 @@ void gk_NonLocalExit_Handler(int signum)
 /**************************************************************************/
 char *gk_strerror(int errnum)
 {
-#if defined(WIN32) || defined(__MINGW32__)
+#if defined(_WIN32) || defined(__MINGW32__)
   return strerror(errnum);
 #else 
 #ifndef SUNOS
diff --git a/src/string.c b/src/string.c
index 4a3fb14..a7fb551 100644
--- a/src/string.c
+++ b/src/string.c
@@ -483,7 +483,7 @@ char *gk_time2str(time_t time)
 
 
 
-#if !defined(WIN32) && !defined(__MINGW32__)
+#if !defined(_WIN32) && !defined(__MINGW32__)
 /************************************************************************/
 /*! \brief Converts a date/time string into its equivalent time_t value
 
diff --git a/src/timers.c b/src/timers.c
index bb8f296..3c4030b 100644
--- a/src/timers.c
+++ b/src/timers.c
@@ -39,7 +39,7 @@ double gk_CPUSeconds(void)
 #ifdef __OPENMPXXXX__
   return omp_get_wtime();
 #else
-  #if defined(WIN32) || defined(__MINGW32__)
+  #if defined(_WIN32) || defined(__MINGW32__)
     return((double) clock()/CLOCKS_PER_SEC);
   #else
     struct rusage r;