cmake: Make build reproducible across different build directories

EchterAgo · EchterAgo · commit 0ae543a94f4a · 2024-02-17T20:01:34.000+07:00
Without this, the usage of the __FILE__ macro leaves the build directory
in the binary. When building the Python extension with build isolation
enabled this would lead to random paths in the binary.
diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
@@ -44,6 +44,17 @@ else()
         -Wall -Wextra -Wno-missing-braces -Werror=undef -Werror=return-type)
 endif()
 
+include (CheckCXXCompilerFlag)
+
+# This is needed for reproducible builds across different build directories.
+# Without this, the usage of the __FILE__ macro leaves the build directory in
+# the binary. When building the Python extension with build isolation enabled
+# this would lead to random paths in the binary.
+set(FILE_PREFIX_ARG "-ffile-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}=")
+check_cxx_compiler_flag("${FILE_PREFIX_ARG}" HAS_FILE_PREFIX_ARG)
+if(HAS_FILE_PREFIX_ARG)
+    set(ZXING_CORE_LOCAL_DEFINES ${ZXING_CORE_LOCAL_DEFINES} "${FILE_PREFIX_ARG}")
+endif()
 
 ################# Source files
 
@@ -458,8 +469,6 @@ target_compile_options (ZXing
     PRIVATE ${ZXING_CORE_LOCAL_DEFINES}
 )
 
-include (CheckCXXCompilerFlag)
-
 target_compile_features(ZXing PUBLIC cxx_std_17)
 
 target_link_libraries (ZXing PRIVATE Threads::Threads)
diff --git a/wrappers/python/CMakeLists.txt b/wrappers/python/CMakeLists.txt
@@ -4,6 +4,15 @@ project(ZXingPython)
 set (pybind11_git_repo https://github.com/pybind/pybind11.git)
 set (pybind11_git_rev v2.11.1)
 
+function(get_core_path REAL_PATH_VAR PATH)
+    if(IS_SYMLINK "${PATH}")
+        get_filename_component(COREPATH "${PATH}" REALPATH)
+        set(${REAL_PATH_VAR} "${COREPATH}" PARENT_SCOPE)
+    else()
+        set(${REAL_PATH_VAR} "${PATH}" PARENT_SCOPE)
+    endif()
+endfunction()
+
 # check if we are called from the top-level ZXing project
 get_directory_property(hasParent PARENT_DIRECTORY)
 if (NOT hasParent)
@@ -17,8 +26,11 @@ if (NOT hasParent)
     option (BUILD_WRITERS "Build with writer support (encoders)" ON)
     option (BUILD_READERS "Build with reader support (decoders)" ON)
     set(BUILD_DEPENDENCIES "AUTO")
-    if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/core)
-        add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/core ZXing EXCLUDE_FROM_ALL)
+    # This is needed because otherwise GCC resolves the symlink which causes paths to randomly
+    # be prefixed by /core or by /wrappers/python/core depending on include order.
+    get_core_path(CORE_REAL_PATH ${CMAKE_CURRENT_SOURCE_DIR}/core)
+    if(EXISTS ${CORE_REAL_PATH})
+        add_subdirectory(${CORE_REAL_PATH} ZXing EXCLUDE_FROM_ALL)
         include(${CMAKE_CURRENT_SOURCE_DIR}/zxing.cmake)
     else()
         message(FATAL_ERROR "Unable to locate zxing source code")
