diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 34d55c7a..0a029e45 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -73,6 +73,11 @@ jobs:
             build/result/index.html
             build/neuron.log
 
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          gcov: true
+
   ft:
     runs-on: ubuntu-20.04
     container: ghcr.io/neugates/build:x86_64-main
@@ -86,7 +91,7 @@ jobs:
         run: |
           git config --global --add safe.directory $(pwd)
           mkdir -p build && cd build
-          cmake .. -DCMAKE_TOOLCHAIN_FILE=../cmake/x86_64-linux-gnu.cmake
+          cmake -DUSE_GCOV=1 .. -DCMAKE_TOOLCHAIN_FILE=../cmake/x86_64-linux-gnu.cmake
           make -j4
 
       - name: function test
@@ -106,6 +111,11 @@ jobs:
             ft/reports/report.html
             build/neuron.log
 
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          gcov: true
+
   pyft:
     runs-on: ubuntu-20.04
     container: ghcr.io/neugates/build:x86_64-main
@@ -119,7 +129,7 @@ jobs:
         run: |
           git config --global --add safe.directory $(pwd)
           mkdir -p build && cd build
-          cmake .. -DCMAKE_TOOLCHAIN_FILE=../cmake/x86_64-linux-gnu.cmake
+          cmake -DUSE_GCOV=1 .. -DCMAKE_TOOLCHAIN_FILE=../cmake/x86_64-linux-gnu.cmake
           make -j4
 
       - name: fetch neu-ft
@@ -139,3 +149,9 @@ jobs:
           name: pyft_result
           path: |
             neu-ft/neuron/report
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          gcov: true            
+
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d545ff00..a1698061 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,7 +33,7 @@ endif()
 
 if(USE_GCOV)
   message(STATUS "using gcov")
-  SET(GCC_COVERAGE_COMPILE_FLAGS "-fprofile-arcs -ftest-coverage")
+  SET(GCC_COVERAGE_COMPILE_FLAGS "-fprofile-arcs -ftest-coverage -O0")
   SET(GCC_COVERAGE_LINK_FLAGS "-lgcov")
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS}")
   SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_COVERAGE_COMPILE_FLAGS}")