commit 56a8fd4062e5dfad2402c59acf210cb64eec4991
from: Sergey Bronnikov <estetus@gmail.com>
date: Wed Jul 10 15:18:15 2024 UTC

cmake: fix searching Clang RT

luzer module requires linking with a library
`clang_rt.fuzzer_no_main-x86_64` that is a part of a Clang runtime.
Without linking with it Lua runtime will report an error right on
loading `luzer.so`:

lua5.1: error loading module 'luzer' from file './luzer.so':
        ./luzer.so: undefined symbol: __sanitizer_cov_8bit_counters_init

The patch adds a module that composes a path to Clang runtime libraries
and adds this path to a library search paths. I suppose in some cases
introduced CMake function may fail. One can pass a path to a directory
with Clang RT manually using environment variable CLANG_RT_LIB_DIR.

In a usual case symbol __sanitizer_cov_8bit_counters_init is added by
compiler on instrumentation when compiler option
-fsanitize-coverage=inline-8bit-counters is specified [1].

1. https://clang.llvm.org/docs/SanitizerCoverage.html

commit - e0ad4cdfda579f7d61ea90428257e0f5d82d86ce
commit + 56a8fd4062e5dfad2402c59acf210cb64eec4991
blob - b2cb78a09071a5d4150c0f266d41669e9757419f
blob + 10ff09c348f161a16e7f4dff1c97729455c93ce8
--- CHANGELOG.md
+++ CHANGELOG.md
@@ -18,3 +18,7 @@ and this project adheres to [Semantic Versioning](http
 ### Changed
 
 - Disable coverage instrumentation of internal functions (#11).
+
+### Fixed
+
+- Fix searching Clang RT.
blob - da1edbdfd954ac1e81a5bc16f705f967cc0ba8bb
blob + 3401739b4c4dfdc78897e54621e6870afb4a6b25
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -5,9 +5,11 @@ project(luzer
   VERSION "1.0.0"
 )
 
+set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+include(SetClangRTLib)
+
 find_package(Lua 5.1 REQUIRED)
 find_package(LLVM REQUIRED CONFIG)
-find_library(LIBRT rt)
 
 set(LUA_NAME "lua${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}")
 find_program(LUA_EXECUTABLE "${LUA_NAME}")
blob - /dev/null
blob + 56debc50de1bd9fde9a63336f9b41df12863109a (mode 644)
--- /dev/null
+++ cmake/SetClangRTLib.cmake
@@ -0,0 +1,40 @@
+# The function sets the given variable in a parent scope to a
+# value in FUZZER_NO_MAIN_LIBRARY environment variable if it
+# is set. Otherwise the value with path to a directory with
+# libclang_rt.fuzzer_no_main library is composed manually.
+# Function raises a fatal message if C compiler is not Clang.
+#
+# $ clang-15 -print-file-name=libclang_rt.fuzzer_no_main-x86_64.a
+# $ /usr/lib/llvm-15/lib/clang/15.0.7/lib/linux/libclang_rt.fuzzer_no_main-x86_64.a
+#
+# On Linux installations libFuzzer library is typically located at:
+#
+# /usr/lib/<llvm-version>/lib/clang/<clang-version>/lib/linux/libclang_rt.fuzzer_no_main-<architecture>.a
+#
+# 1. https://llvm.org/docs/LibFuzzer.html#using-libfuzzer-as-a-library
+
+function(SetFuzzerNoMainLibPath outvar)
+  if (NOT CMAKE_C_COMPILER_ID STREQUAL "Clang")
+    message(FATAL_ERROR "C compiler is not a Clang")
+  endif ()
+
+  if (CMAKE_SIZEOF_VOID_P EQUAL 4)
+    set(ARCH "i386")
+  elseif (CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(ARCH "x86_64")
+  else ()
+    message(FATAL_ERROR "Unsupported architecture.")
+  endif ()
+
+  set(LIB_FUZZER_NO_MAIN "libclang_rt.fuzzer_no_main-${ARCH}.a")
+  execute_process(COMMAND ${CMAKE_C_COMPILER} "-print-file-name=${LIB_FUZZER_NO_MAIN}"
+    RESULT_VARIABLE CMD_ERROR
+    OUTPUT_VARIABLE CMD_OUTPUT
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+  if (CMD_ERROR)
+    message(FATAL_ERROR "${CMD_ERROR}")
+  endif ()
+  set(${outvar} ${CMD_OUTPUT} PARENT_SCOPE)
+  message(STATUS "[SetClangRTLib] ${outvar} is ${CMD_OUTPUT}")
+endfunction()
blob - 785a9e297fabab0f521d678b5d673a9840829a24
blob + 4f76421a49c64be403566d3f75ae3e1a88932534
--- luzer/CMakeLists.txt
+++ luzer/CMakeLists.txt
@@ -1,18 +1,5 @@
-# Locate compiler-rt libraries.
-# Location is LLVM_LIBRARY_DIRS/clang/<version>/lib/<OS>/,
-# for example LLVM_LIBRARY_DIRS/clang/4.0.0/lib/darwin/.
-#
-# See https://llvm.org/docs/LibFuzzer.html#using-libfuzzer-as-a-library
+SetFuzzerNoMainLibPath(FUZZER_NO_MAIN_LIBRARY)
 
-set(LLVM_BASE ${LLVM_LIBRARY_DIRS}/clang/${LLVM_PACKAGE_VERSION})
-string(TOLOWER ${CMAKE_HOST_SYSTEM_NAME} OS_NAME)
-set(LIBCLANG_RT ${LLVM_BASE}/lib/${OS_NAME}/libclang_rt.fuzzer_no_main-x86_64.a)
-if(EXISTS ${LIBCLANG_RT})
-  message(STATUS "Found libclang_rt ${LIBCLANG_RT}")
-else()
-  message(FATAL_ERROR "libclang_rt is not found")
-endif()
-
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/version.c
   ${CMAKE_CURRENT_BINARY_DIR}/version.c
@@ -31,9 +18,8 @@ target_include_directories(${CMAKE_PROJECT_NAME} PRIVA
 )
 target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE
 	${LUA_LIBRARIES}
-	${LIBRT}
-	${LIBCLANG_RT}
 	-fsanitize=fuzzer-no-link
+	${FUZZER_NO_MAIN_LIBRARY}
 )
 target_compile_options(${CMAKE_PROJECT_NAME} PRIVATE
 	-D_FORTIFY_SOURCE=2