From c687cfb25a8d0ba44af15e8f3ce1af4d76a89e4b Mon Sep 17 00:00:00 2001
From: Gideon Geier <43006546+ggeier@users.noreply.github.com>
Date: Thu, 5 Mar 2026 11:15:56 +0100
Subject: [PATCH 1/2] Add clang coverage build target driven by tests

---
 CMakeLists.txt      | 50 +++++++++++++++++++++++++++++++++++++++++++++
 README.md           |  7 +++++++
 test/CMakeLists.txt |  4 +++-
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d34e46bf..627a9183 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,6 +4,8 @@ project(
   VERSION 0.1
   LANGUAGES C CXX)
 
+option(COLDTRACE_ENABLE_COVERAGE "Enable Clang coverage instrumentation" OFF)
+
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 add_compile_definitions(LOG_PREFIX="coldtrace: ")
@@ -21,8 +23,19 @@ endif()
 
 add_compile_options(-fPIC -g3 -D_GNU_SOURCE -DDICE_MAIN_START_DISABLE)
 set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+if(COLDTRACE_ENABLE_COVERAGE)
+  set(CMAKE_INTERPROCEDURAL_OPTIMIZATION FALSE)
+endif()
 set(DICE_MEMSET ON)
 
+if(COLDTRACE_ENABLE_COVERAGE)
+  if(NOT CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    message(FATAL_ERROR "COLDTRACE_ENABLE_COVERAGE requires Clang")
+  endif()
+  add_compile_options(-fprofile-instr-generate -fcoverage-mapping)
+  add_link_options(-fprofile-instr-generate)
+endif()
+
 add_subdirectory(deps/dice)
 find_package(libvsync 4.2 CONFIG)
 if(NOT libvsync_DIR)
@@ -48,6 +61,43 @@ add_subdirectory(src)
 enable_testing()
 add_subdirectory(test)
 
+if(COLDTRACE_ENABLE_COVERAGE)
+  find_program(LLVM_PROFDATA_TOOL llvm-profdata REQUIRED)
+  find_program(LLVM_COV_TOOL llvm-cov REQUIRED)
+
+  get_property(COLDTRACE_TEST_TARGETS GLOBAL PROPERTY COLDTRACE_TEST_TARGETS)
+  set(COVERAGE_DIR ${CMAKE_CURRENT_BINARY_DIR}/coverage)
+  set(COVERAGE_PROFILE ${COVERAGE_DIR}/coldtrace.profraw)
+  set(COVERAGE_DATA ${COVERAGE_DIR}/coldtrace.profdata)
+
+  if(NOT COLDTRACE_TEST_TARGETS)
+    message(FATAL_ERROR "No test targets were found for coverage generation")
+  endif()
+  list(GET COLDTRACE_TEST_TARGETS 0 COVERAGE_MAIN_TARGET)
+
+  set(COVERAGE_OBJECTS)
+  foreach(TARGET ${COLDTRACE_TEST_TARGETS})
+    list(APPEND COVERAGE_OBJECTS -object=$<TARGET_FILE:${TARGET}>)
+  endforeach()
+  string(JOIN " " COVERAGE_OBJECTS_STR ${COVERAGE_OBJECTS})
+
+  add_custom_target(
+    coverage
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${COVERAGE_DIR}
+    COMMAND ${CMAKE_COMMAND} -E env LLVM_PROFILE_FILE=${COVERAGE_PROFILE}
+            ${CMAKE_CTEST_COMMAND} --output-on-failure
+    COMMAND ${LLVM_PROFDATA_TOOL} merge -sparse ${COVERAGE_PROFILE} -o
+            ${COVERAGE_DATA}
+    COMMAND ${LLVM_COV_TOOL} report
+            $<TARGET_FILE:${COVERAGE_MAIN_TARGET}>
+            ${COVERAGE_OBJECTS}
+            -instr-profile=${COVERAGE_DATA}
+    COMMAND bash -lc "${LLVM_COV_TOOL} export -format=lcov $<TARGET_FILE:${COVERAGE_MAIN_TARGET}> ${COVERAGE_OBJECTS_STR} -instr-profile=${COVERAGE_DATA} > ${COVERAGE_DIR}/coverage.lcov"
+    DEPENDS ${COLDTRACE_TEST_TARGETS}
+    USES_TERMINAL
+    COMMENT "Running tests and producing a Clang coverage report")
+endif()
+
 file(GLOB_RECURSE ALL_SOURCE_FILES
     ${CMAKE_SOURCE_DIR}/src/*.cpp
     ${CMAKE_SOURCE_DIR}/src/*.c
diff --git a/README.md b/README.md
index 3b223b51..236fd67c 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,13 @@ See the log output (optional):
 
     scripts/trace_dump.py traces/freezer_log_1_0.bin
 
+Run tests and generate a Clang coverage report (optional):
+
+    cmake -S . -Bbuild-coverage -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCOLDTRACE_ENABLE_COVERAGE=ON
+    cmake --build build-coverage --target coverage
+
+Coverage output files are written to `build-coverage/coverage/`.
+
 Run freezer analysis (optional):
 
     freezer -f traces
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 756d305a..c70a7f75 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -27,10 +27,12 @@ foreach(SRC ${SRCS})
   target_link_options(${TARGET} PRIVATE -fsanitize=thread)
   if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
     target_compile_options(${TARGET} PRIVATE -Wno-use-after-free)
-  elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+  elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND NOT COLDTRACE_ENABLE_COVERAGE)
     target_link_options(${TARGET} PRIVATE -shared-libsan)
   endif()
 
+  set_property(GLOBAL APPEND PROPERTY COLDTRACE_TEST_TARGETS ${TARGET})
+
   # if this is a trace test, we also link with mock_checker and set the test
   # runner accordingly
   if(${TARGET} MATCHES "^trace_.*")

From f39a72339b148eb355abede32c40ed0eaba65374 Mon Sep 17 00:00:00 2001
From: Gideon Geier <43006546+ggeier@users.noreply.github.com>
Date: Thu, 5 Mar 2026 11:28:41 +0100
Subject: [PATCH 2/2] Fix clang test linking in coverage builds

---
 test/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c70a7f75..63160894 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -27,7 +27,7 @@ foreach(SRC ${SRCS})
   target_link_options(${TARGET} PRIVATE -fsanitize=thread)
   if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
     target_compile_options(${TARGET} PRIVATE -Wno-use-after-free)
-  elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND NOT COLDTRACE_ENABLE_COVERAGE)
+  elseif(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_link_options(${TARGET} PRIVATE -shared-libsan)
   endif()