diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ff96cf8..0c2166d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,8 +26,14 @@ jobs:
     - name: Install Python dependencies
       run: python -m pip install -e .[dev]
 
-    - name: Build ops obj files and runner
-      run: bash src/copapy/obj/nativecompile.sh
+    - name: Build ops obj files
+      run: |
+        bash src/copapy/obj/nativecompile.sh
+
+    - name: Compile coparun
+      run: |
+        mkdir -p bin
+        gcc -O3 -Wall -Wextra -Wconversion -Wsign-conversion -Wshadow -Wstrict-overflow -Werror -g src/coparun/runmem.c src/coparun/coparun.c src/coparun/mem_man.c -o bin/coparun
 
     #- name: Lint code with flake8
     #  run: flake8
@@ -82,7 +88,7 @@ jobs:
       with:
         vs-version: 'latest'
 
-    - name: Compile
+    - name: Compile coparun
       shell: cmd
       run: |
         mkdir bin
diff --git a/notes/crash_windows.md b/notes/crash_windows.md
index d9c7240..df094ba 100644
--- a/notes/crash_windows.md
+++ b/notes/crash_windows.md
@@ -10,7 +10,7 @@ optimization (/O2). For MSVC without optimization and gcc with -O3 there is no i
 
 The callee code is composed of stencils build with gcc-12 -O3:
 
-``` bash
+```
     1000:       f3 0f 1e fa             endbr64
     1004:       48 83 ec 08             sub    $0x8,%rsp
     1008:       31 ff                   xor    %edi,%edi
@@ -35,7 +35,7 @@ The callee code is composed of stencils build with gcc-12 -O3:
 
 ## Caller
 
-The caller (src/copapy/runmem.c):
+The caller (src/copapy/runmem.c) calls the callee (here named "entr_point") like so:
 
 ``` c
 case RUN_PROG:
@@ -51,7 +51,7 @@ case RUN_PROG:
 
 Compiled with MSVC and optimization (crash):
 
-``` bash
+```
   00000001400078CA: 8B 1E              mov         ebx,dword ptr [rsi]
   00000001400078CC: 48 8D 0D AD 30 08  lea         rcx,[??_C@_0BM@DFBMBFEB@RUN_PROG?5rel_entr_point?$DN?$CFi?6@]
                     00
@@ -75,7 +75,7 @@ Compiled with MSVC and optimization (crash):
 
 Compiled with MSVC and no optimization (no crash):
 
-``` bash
+```
   0000000140007978: 48 8B 44 24 70     mov         rax,qword ptr [rsp+70h]
   000000014000797D: 8B 00              mov         eax,dword ptr [rax]
   000000014000797F: 89 44 24 4C        mov         dword ptr [rsp+4Ch],eax
diff --git a/src/copapy/generate_stencils.py b/src/copapy/generate_stencils.py
index d7cf2e8..ce45862 100644
--- a/src/copapy/generate_stencils.py
+++ b/src/copapy/generate_stencils.py
@@ -7,7 +7,7 @@ op_signs = {'add': '+', 'sub': '-', 'mul': '*', 'div': '/',
 
 def get_function_start() -> str:
     return """
-    int function_start(){
+    __attribute__((ms_abi)) int function_start(){
         result_int(0);  // dummy call instruction before marker gets striped
         asm volatile (".long 0xE2401F0F");
         return 1;
@@ -17,7 +17,7 @@ def get_function_start() -> str:
 
 def get_function_end() -> str:
     return """
-    int function_end(){
+    __attribute__((ms_abi)) int function_end(){
         result_int(0);
         asm volatile (".long 0xE1401F0F");
         return 1;