cmake: tweak linker source initialization

The current approach with a global property is a little hacky and
doesn't reflect the intent of the zephyr_linker_sources() call in
boilerplate.cmake. Add a separate helper for initializing the
files to at least avoid using the global property.

It would be even nicer to manage these as generated files which the
link steps depend on, but this is a start.

Signed-off-by: Marti Bolivar <[email protected]>

Author: mbolivar-nordic

cmake/app/boilerplate.cmake

@@ -86,8 +86,11 @@ add_custom_target(
   # Equivalent to rm -rf build/*
   )
 
-# Dummy add to generate files.
-zephyr_linker_sources(SECTIONS)
+# Zephyr's linker scripts are the result of running the C preprocessor
+# on per-architecture files. These files can include various sources from
+# around the zephyr tree using the zephyr_linker_sources() mechanism.
+# This helper is used to set up these files.
+zephyr_init_linker_sources()
 
 # The BOARD can be set by 3 sources. Through environment variables,
 # through the cmake CLI, and through CMakeLists.txt.

cmake/extensions.cmake

@@ -841,26 +841,16 @@ endfunction()
 # Friendly reminder: Beware of the different ways the location counter ('.')
 # behaves inside vs. outside section definitions.
 function(zephyr_linker_sources location)
-  # Set up the paths to the destination files. These files are #included inside
-  # the global linker.ld.
+  # Set up the paths to the destination files. These files are
+  # #included inside the global linker.ld. Keep these settings in sync
+  # with zephyr_init_linker_sources().
   set(snippet_base      "${__build_dir}/include/generated")
   set(sections_path     "${snippet_base}/snippets-sections.ld")
   set(ram_sections_path "${snippet_base}/snippets-ram-sections.ld")
   set(noinit_path       "${snippet_base}/snippets-noinit.ld")
   set(rwdata_path       "${snippet_base}/snippets-rwdata.ld")
   set(rodata_path       "${snippet_base}/snippets-rodata.ld")
 
-  # Clear destination files if this is the first time the function is called.
-  get_property(cleared GLOBAL PROPERTY snippet_files_cleared)
-  if (NOT DEFINED cleared)
-    file(WRITE ${sections_path} "")
-    file(WRITE ${ram_sections_path} "")
-    file(WRITE ${noinit_path} "")
-    file(WRITE ${rwdata_path} "")
-    file(WRITE ${rodata_path} "")
-    set_property(GLOBAL PROPERTY snippet_files_cleared true)
-  endif()
-
   # Choose destination file, based on the <location> argument.
   if ("${location}" STREQUAL "SECTIONS")
     set(snippet_path "${sections_path}")
@@ -896,6 +886,21 @@ function(zephyr_linker_sources location)
   endforeach()
 endfunction(zephyr_linker_sources)
 
+# Private helper to initialize zephyr_linker_sources()
+function(zephyr_init_linker_sources)
+  set(snippet_base      "${__build_dir}/include/generated")
+  set(sections_path     "${snippet_base}/snippets-sections.ld")
+  set(ram_sections_path "${snippet_base}/snippets-ram-sections.ld")
+  set(noinit_path       "${snippet_base}/snippets-noinit.ld")
+  set(rwdata_path       "${snippet_base}/snippets-rwdata.ld")
+  set(rodata_path       "${snippet_base}/snippets-rodata.ld")
+
+  file(WRITE ${sections_path} "")
+  file(WRITE ${ram_sections_path} "")
+  file(WRITE ${noinit_path} "")
+  file(WRITE ${rwdata_path} "")
+  file(WRITE ${rodata_path} "")
+endfunction()
 
 # Helper function for CONFIG_CODE_DATA_RELOCATION
 # Call this function with 2 arguments file and then memory location