diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 73c2dfa1e..55238bf11 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -71,6 +71,11 @@ jobs:
           cd test
           ..\build\${{ matrix.build_type }}\c3c.exe compile-test unit -O1
 
+      - name: Test python script
+        run: |
+          py msvc_build_libraries.py --accept-license
+          dir msvc_sdk
+
       - name: upload artifacts
         uses: actions/upload-artifact@v3
         with:
@@ -193,7 +198,7 @@ jobs:
       fail-fast: false
       matrix:
         build_type: [Release, Debug]
-        llvm_version: [15, 16, 17, 18]
+        llvm_version: [15, 16, 17, 18, 19]
 
     steps:
       - uses: actions/checkout@v4
@@ -207,7 +212,7 @@ jobs:
           if [[ "${{matrix.llvm_version}}" < 16 ]]; then
             sudo apt remove libllvm15
           fi
-          if [[ "${{matrix.llvm_version}}" < 18 ]]; then
+          if [[ "${{matrix.llvm_version}}" < 19 ]]; then
             sudo add-apt-repository "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-${{matrix.llvm_version}} main"
             sudo apt-get update
             sudo apt-get install -y -t llvm-toolchain-focal-${{matrix.llvm_version}} libpolly-${{matrix.llvm_version}}-dev \
@@ -222,6 +227,7 @@ jobs:
               libmlir-${{matrix.llvm_version}}-dev mlir-${{matrix.llvm_version}}-tools 
           fi
       - name: CMake
+        if: matrix.llvm_version != 18
         run: |
           cmake -B build \
                 -G Ninja \
@@ -234,6 +240,20 @@ jobs:
                 -DCMAKE_DLLTOOL=llvm-dlltool-${{matrix.llvm_version}} \
                 -DC3_LLVM_VERSION=${{matrix.llvm_version}}
           cmake --build build
+      - name: CMake18
+        if: matrix.llvm_version == 18
+        run: |
+          cmake -B build \
+                -G Ninja \
+                -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
+                -DCMAKE_C_COMPILER=clang-${{matrix.llvm_version}} \
+                -DCMAKE_CXX_COMPILER=clang++-${{matrix.llvm_version}} \
+                -DCMAKE_LINKER=lld-link-${{matrix.llvm_version}} \
+                -DCMAKE_OBJCOPY=llvm-objcopy-${{matrix.llvm_version}} \
+                -DCMAKE_STRIP=llvm-strip-${{matrix.llvm_version}} \
+                -DCMAKE_DLLTOOL=llvm-dlltool-${{matrix.llvm_version}} \
+                -DC3_LLVM_VERSION=18.1
+          cmake --build build
 
       - name: Compile and run some examples
         run: |
@@ -418,7 +438,7 @@ jobs:
       fail-fast: false
       matrix:
         build_type: [Release, Debug]
-        llvm_version: [15, 16]
+        llvm_version: [15, 16, 17]
     steps:
       - uses: actions/checkout@v4
       - name: Download LLVM
diff --git a/CMakeLists.txt b/CMakeLists.txt
index db94474a7..87921fd6e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -75,7 +75,7 @@ if (NOT WIN32)
     find_package(CURL)
 endif()
 if (NOT C3_LLVM_VERSION STREQUAL "auto")
-    if (${C3_LLVM_VERSION} VERSION_LESS 15 OR ${C3_LLVM_VERSION} VERSION_GREATER 18)
+    if (${C3_LLVM_VERSION} VERSION_LESS 15 OR ${C3_LLVM_VERSION} VERSION_GREATER 19)
         message(FATAL_ERROR "LLVM ${C3_LLVM_VERSION} is not supported!")
     endif()
 endif()
diff --git a/lib/std/core/mem.c3 b/lib/std/core/mem.c3
index 7c94a37c8..f9755276b 100644
--- a/lib/std/core/mem.c3
+++ b/lib/std/core/mem.c3
@@ -430,7 +430,7 @@ macro void @pool(TempAllocator* #other_temp = null; @body) @builtin
 		TempAllocator* original = current;
 		if (current == (void*)#other_temp) current = allocator::temp_allocator_next();
 	$endif
-	usz mark = current.mark();
+	usz mark = current.used;
 	defer
 	{
 		current.reset(mark);