cpio.cmake: Improve CPIO creation maintainability

Signed-off-by: Axel Heider <[email protected]>

cmake-tool/helpers/cpio.cmake

@@ -48,27 +48,47 @@ function(MakeCPIO output_name input_files)
     set(cpio_archive "archive.${output_name}.cpio")
     set(cpio_archive_s "${output_name}.S")
 
-    # Check that the reproducible flag is available. Don't use it if it isn't.
+    # Try to generate reproducible cpio archives using a command sequence that
+    # runs in a separate shell in a temp folder. It creates an empty archive and
+    # then adds the files in the given order - which may differ from the
+    # alphabetical order, but some caller require the given order also.
+    # With "touch -d @0 <file>" the 'modified time' is set to 0. The cpio
+    # parameter "--owner=+0:+0" sets user and group values to 0:0. For some cpio
+    # version "--reproducible" is available, if this is the case the archive is
+    # created with consistent inodes and device numbering.
     CheckCPIOArgument(cpio_reproducible_flag "--reproducible")
     set(
         cpio_cmd
         "cpio ${cpio_reproducible_flag} --quiet --create --format=newc --file=${CMAKE_CURRENT_BINARY_DIR}/${cpio_archive}"
     )
 
     set(tmp_dir "temp_${output_name}")
-    set(commands "bash;-c;${cpio_cmd};&&")
+    set(make_cpio "cd ${tmp_dir} && ${cpio_cmd}")
     foreach(file IN LISTS input_files)
-        # Try and generate reproducible cpio meta-data as we do this:
-        # - touch -d @0 file sets the modified time to 0
-        # - --owner=root:root sets user and group values to 0:0
-        # - --reproducible creates reproducible archives with consistent inodes and device numbering
-        list(
+        string(
             APPEND
-                commands
-                "bash;-c; mkdir -p ${tmp_dir} && cd ${tmp_dir} && cp -a ${file} . && touch -d @0 `basename ${file}` && echo `basename ${file}` | ${cpio_cmd} --append --owner=+0:+0 && rm `basename ${file}` && cd ../ && rmdir ${tmp_dir};&&"
+            make_cpio
+            " && cp -a \"${file}\" ."
+            " && touch -d @0 `basename ${file}`"
+            " && echo `basename ${file}` | ${cpio_cmd} --append --owner=+0:+0"
         )
     endforeach()
-    list(APPEND commands "true")
+
+    # create a "program" that makes the compiler generate and object file that
+    # contains the cpio archive.
+    file(
+        WRITE
+            "${cpio_archive_s}"
+            "# auto-generated file from MakeCPIO(), do not edit\n"
+            ".section ._archive_cpio, \"aw\"\n"
+            ".globl ${archive_symbol}, ${archive_symbol}_end\n"
+            "${archive_symbol}:\n"
+            ".incbin \"${cpio_archive}\"\n"
+            "${archive_symbol}_end:\n"
+    )
+
+    # re-run CMake configuration in case ${cpio_archive_s} is deleted
+    set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS "${cpio_archive_s}")
 
     separate_arguments(cmake_c_flags_sep NATIVE_COMMAND "${CMAKE_C_FLAGS}")
     if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
@@ -78,18 +98,13 @@ function(MakeCPIO output_name input_files)
     add_custom_command(
         OUTPUT ${output_name}
         COMMAND rm -f ${cpio_archive}
-        COMMAND ${commands}
         COMMAND
-            sh -c
-            "echo 'X.section ._archive_cpio,\"aw\"X.globl ${archive_symbol}, ${archive_symbol}_endX${archive_symbol}:X.incbin \"${cpio_archive}\"X${archive_symbol}_end:X' | tr X '\\n'"
-            > "${cpio_archive_s}"
+            mkdir -p ${tmp_dir} && bash -c "${make_cpio}" && rm -rf ${tmp_dir}/
         COMMAND
             ${CMAKE_C_COMPILER} ${cmake_c_flags_sep} -c -o ${output_name} "${cpio_archive_s}"
         DEPENDS ${input_files} ${MAKE_CPIO_DEPENDS}
-        VERBATIM
-        BYPRODUCTS
-        "${cpio_archive}"
-        "${cpio_archive_s}"
+        VERBATIM BYPRODUCTS "${cpio_archive}"
+        DEPENDS "${cpio_archive_s}"
         COMMENT "Generate CPIO archive ${output_name}"
     )
 endfunction(MakeCPIO)