cmake: Full reproducibility support

CMakeLists.txt

@@ -1,7 +1,8 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.19)
 include(cmake/Utilities.cmake)
 include(cmake/GetGitRevisionDescription.cmake)
 include(cmake/ProjectVersion.cmake)
+include(cmake/ReproducibleBuild.cmake)
 
 project(
   MMU
@@ -95,12 +96,8 @@ add_compile_options(-g)
 
 # optimizations
 if(CMAKE_CROSSCOMPILING)
-  # Reproducible build support
-  add_link_options(-fdebug-prefix-map=${CMAKE_SOURCE_DIR}=)
-  add_link_options(-fdebug-prefix-map=${CMAKE_BINARY_DIR}=)
-  if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "8")
-    add_compile_options(-ffile-prefix-map=${CMAKE_SOURCE_DIR}=)
-  endif()
+  # TODO: get date from the last git commit to set as epoch
+  set_source_epoch(0)
 
   # default optimization flags
   set(CMAKE_CXX_FLAGS_DEBUG "-Og -g")
@@ -203,7 +200,9 @@ target_compile_options(firmware PRIVATE -Wdouble-promotion)
 
 add_subdirectory(src)
 
-if(NOT CMAKE_CROSSCOMPILING)
+if(CMAKE_CROSSCOMPILING)
+  set_all_targets_reproducible()
+else()
   # do not build the firmware by default (tests are the focus if not crosscompiling)
   set_target_properties(firmware PROPERTIES EXCLUDE_FROM_ALL YES)
 

cmake/ReproducibleBuild.cmake

@@ -0,0 +1,66 @@
+#
+# Functions and utilities for build reproducibility
+#
+
+# Set a target to be reproducible
+function(set_reproducible_target target)
+  # properties for static libraries
+  set_target_properties(${target} PROPERTIES STATIC_LIBRARY_OPTIONS "-D")
+
+  # properties on executables
+  target_link_options(${target} PRIVATE -fdebug-prefix-map=${CMAKE_SOURCE_DIR}=)
+  target_link_options(${target} PRIVATE -fdebug-prefix-map=${CMAKE_BINARY_DIR}=)
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "8")
+    target_compile_options(${target} PRIVATE -ffile-prefix-map=${CMAKE_SOURCE_DIR}=)
+  endif()
+
+  # properties on sources
+  get_target_property(sources ${target} SOURCES)
+  get_target_property(source_dir ${target} SOURCE_DIR)
+  foreach(file IN LISTS sources)
+    cmake_path(ABSOLUTE_PATH file BASE_DIRECTORY ${source_dir})
+    cmake_path(RELATIVE_PATH file BASE_DIRECTORY ${CMAKE_SOURCE_DIR} OUTPUT_VARIABLE rpath)
+    set_property(
+      SOURCE ${file}
+      DIRECTORY ${source_dir}
+      APPEND
+      PROPERTY COMPILE_OPTIONS "-frandom-seed=${rpath}"
+      )
+  endforeach()
+endfunction()
+
+# Get the list of targets for all directories
+function(get_all_targets _result _dir)
+  get_property(
+    _subdirs
+    DIRECTORY "${_dir}"
+    PROPERTY SUBDIRECTORIES
+    )
+  foreach(_subdir IN LISTS _subdirs)
+    get_all_targets(${_result} "${_subdir}")
+  endforeach()
+  get_directory_property(_sub_targets DIRECTORY "${_dir}" BUILDSYSTEM_TARGETS)
+  set(${_result}
+      ${${_result}} ${_sub_targets}
+      PARENT_SCOPE
+      )
+endfunction()
+
+# Make every target reproducible
+function(set_all_targets_reproducible)
+  get_all_targets(targets ${CMAKE_SOURCE_DIR})
+  foreach(target IN LISTS targets)
+    set_reproducible_target(${target})
+  endforeach()
+endfunction()
+
+# Set source epoch
+function(set_source_epoch epoch)
+  set(ENV{SOURCE_DATE_EPOCH} ${epoch})
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "8")
+    string(TIMESTAMP SOURCE_DATE_EPOCH "%Y-%m-%d")
+    add_compile_definitions(SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH}")
+    string(TIMESTAMP SOURCE_TIME_EPOCH "%H:%M:%S")
+    add_compile_definitions(SOURCE_TIME_EPOCH="${SOURCE_TIME_EPOCH}")
+  endif()
+endfunction()