llext-edk: add module settings to exported EDK

CMakeLists.txt

@@ -2288,22 +2288,13 @@ if(CONFIG_LLEXT_EDK)
   endif()
   set(llext_edk_file ${PROJECT_BINARY_DIR}/${CONFIG_LLEXT_EDK_NAME}.${llext_edk_extension})
 
-  # TODO maybe generate flags for C CXX ASM
-  zephyr_get_compile_definitions_for_lang(C zephyr_defs)
-  zephyr_get_compile_options_for_lang(C zephyr_flags)
-
-  # Filter out non LLEXT and LLEXT_EDK flags - and add required ones
-  llext_filter_zephyr_flags(LLEXT_REMOVE_FLAGS ${zephyr_flags} llext_filt_flags)
-  llext_filter_zephyr_flags(LLEXT_EDK_REMOVE_FLAGS ${llext_filt_flags} llext_filt_flags)
-
-  set(llext_edk_cflags ${zephyr_defs} -DLL_EXTENSION_BUILD)
-  list(APPEND llext_edk_cflags ${llext_filt_flags})
-  list(APPEND llext_edk_cflags ${LLEXT_APPEND_FLAGS})
-  list(APPEND llext_edk_cflags ${LLEXT_EDK_APPEND_FLAGS})
-
+  # Export current settings for use in LLEXT EDK generation
   build_info(llext-edk file PATH ${llext_edk_file})
-  build_info(llext-edk cflags VALUE ${llext_edk_cflags})
-  build_info(llext-edk include-dirs VALUE "$<TARGET_PROPERTY:zephyr_interface,INTERFACE_INCLUDE_DIRECTORIES>")
+  build_info(llext-edk remove-cflags VALUE ${LLEXT_REMOVE_FLAGS} ${LLEXT_EDK_REMOVE_FLAGS})
+  build_info(llext-edk append-cflags VALUE ${LLEXT_APPEND_FLAGS} ${LLEXT_EDK_APPEND_FLAGS} -DLL_EXTENSION_BUILD)
+
+  # Generate the compiler flag files that will be used by the EDK
+  add_subdirectory(misc/llext_edk)
 
   add_custom_command(
     OUTPUT ${llext_edk_file}
@@ -2322,7 +2313,7 @@ if(CONFIG_LLEXT_EDK)
       ${SYSCALL_SPLIT_TIMEOUT_ARG}
     COMMAND ${CMAKE_COMMAND}
         -P ${ZEPHYR_BASE}/cmake/llext-edk.cmake
-    DEPENDS ${logical_target_for_zephyr_elf} ${syscalls_json} build_info_yaml_saved
+    DEPENDS ${logical_target_for_zephyr_elf} ${syscalls_json} build_info_yaml_saved llext_edk_build_props
     COMMAND_EXPAND_LISTS
   )
   add_custom_target(llext-edk DEPENDS ${llext_edk_file})

cmake/llext-edk.cmake

@@ -3,7 +3,7 @@
 
 # This script generates a tarball containing all headers and flags necessary to
 # build an llext extension. It does so by copying all headers accessible from
-# INTERFACE_INCLUDE_DIRECTORIES and generating a Makefile.cflags file (and a
+# a C compiler command line and generating a Makefile.cflags file (and a
 # cmake.cflags one) with all flags necessary to build the extension.
 #
 # The tarball can be extracted and used in the extension build system to include
@@ -152,12 +152,34 @@ if (CONFIG_LLEXT_EXPORT_BUILTINS_BY_SLID)
     "The LLEXT EDK is not compatible with CONFIG_LLEXT_EXPORT_BUILTINS_BY_SLID.")
 endif()
 
+set(build_flags_dir ${PROJECT_BINARY_DIR}/misc/llext_edk)
 set(build_info_file ${PROJECT_BINARY_DIR}/../build_info.yml)
 yaml_load(FILE ${build_info_file} NAME build_info)
 
-yaml_get(llext_edk_cflags NAME build_info KEY cmake llext-edk cflags)
+# process C flags
+file(READ ${build_flags_dir}/c_flags.txt llext_edk_c_flags_raw)
+string(STRIP ${llext_edk_c_flags_raw} llext_edk_c_flags)
+string(REPLACE " " ";" llext_edk_cflags "${llext_edk_c_flags}")
+yaml_get(llext_remove_cflags NAME build_info KEY cmake llext-edk remove-cflags)
+yaml_get(llext_append_cflags NAME build_info KEY cmake llext-edk append-cflags)
+foreach(item IN_LIST ${llext_remove_cflags})
+  list(FILTER llext_edk_cflags EXCLUDE REGEX "^${item}$")
+endforeach()
+list(APPEND llext_edk_cflags ${llext_append_cflags})
+
+# process C definitions
+file(READ ${build_flags_dir}/c_defs.txt llext_edk_c_defs_raw)
+string(STRIP ${llext_edk_c_defs_raw} llext_edk_c_defs)
+string(REPLACE " " ";" llext_edk_c_defs "${llext_edk_c_defs}")
+list(PREPEND llext_edk_cflags ${llext_edk_c_defs})
+
+# process C include directories
+file(READ ${build_flags_dir}/c_incs.txt llext_edk_c_incs_raw)
+string(STRIP ${llext_edk_c_incs_raw} llext_edk_c_incs)
+string(REPLACE " " ";" llext_edk_c_incs "${llext_edk_c_incs}")
+list(TRANSFORM llext_edk_c_incs REPLACE "^-I" "")
+
 yaml_get(llext_edk_file NAME build_info KEY cmake llext-edk file)
-yaml_get(INTERFACE_INCLUDE_DIRECTORIES NAME build_info KEY cmake llext-edk include-dirs)
 yaml_get(APPLICATION_SOURCE_DIR NAME build_info KEY cmake application source-dir)
 yaml_get(WEST_TOPDIR NAME build_info KEY west topdir)
 
@@ -210,8 +232,8 @@ set(llext_edk_cflags ${new_cflags})
 list(APPEND base_flags ${llext_edk_cflags} ${imacros})
 
 file(MAKE_DIRECTORY ${llext_edk_inc})
-foreach(dir ${INTERFACE_INCLUDE_DIRECTORIES})
-    if (NOT EXISTS ${dir})
+foreach(dir ${llext_edk_c_incs})
+    if(NOT EXISTS ${dir})
         continue()
     endif()
 

misc/llext_edk/CMakeLists.txt

@@ -0,0 +1,29 @@
+# Copyright 2025 Arduino SA
+# SPDX-License-Identifier: Apache-2.0
+
+# This CMake script is used to capture the full set of build properties for the
+# Zephyr 'app' target so that it can be properly exported by the EDK build
+# system.
+
+# Getting the whole list of build properties via CMake functions is tricky.
+# The 'app' target is not fully configured at the time Zephyr scripts are
+# included, so querying its properties directly would yield incomplete results.
+# However, using CMake generator expressions is also forbidden, since the
+# properties include $<COMPILE_LANGUAGE:...> entries, and CMake does not know
+# how to resolve those outside of a proper compile context.
+
+# To work around this, the following code creates a dummy target that imports
+# build configuration from 'app', but overrides the C compile rules to simply
+# output the resulting properties to text files. The EDK will then read those
+# text files to get the full set of build properties.
+
+unset(CMAKE_C_COMPILER_LAUNCHER)
+unset(CMAKE_DEPFILE_FLAGS_C)
+set(CMAKE_C_COMPILE_OBJECT
+    "${CMAKE_COMMAND} -E echo '<DEFINES>' > ${CMAKE_CURRENT_BINARY_DIR}/c_defs.txt"
+    "${CMAKE_COMMAND} -E echo '<INCLUDES>' > ${CMAKE_CURRENT_BINARY_DIR}/c_incs.txt"
+    "${CMAKE_COMMAND} -E echo '<FLAGS>' > ${CMAKE_CURRENT_BINARY_DIR}/c_flags.txt"
+    "${CMAKE_C_COMPILE_OBJECT}")
+
+add_library(llext_edk_build_props ${ZEPHYR_BASE}/misc/empty_file.c)
+target_link_libraries(llext_edk_build_props PUBLIC app)

scripts/schemas/build-schema.yml

@@ -85,13 +85,13 @@ mapping:
       llext-edk:
         type: map
         mapping:
-          cflags:
+          file:
+            type: str
+          remove-cflags:
             type: seq
             sequence:
               - type: str
-          file:
-            type: str
-          include-dirs:
+          append-cflags:
             type: seq
             sequence:
               - type: str

tests/misc/llext-edk/CMakeLists.txt

@@ -2,11 +2,17 @@
 
 cmake_minimum_required(VERSION 3.20.0)
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+
+# verify information from dependencies is available to extensions
+add_library(dependency INTERFACE)
+target_compile_definitions(dependency INTERFACE GLOBAL_OPT="set")
+
 project(llext_edk_test LANGUAGES C)
 
 target_sources(app PRIVATE src/main.c src/foo.c)
 zephyr_include_directories(include)
 zephyr_include_directories(${ZEPHYR_BASE}/boards/native/common)
+target_link_libraries(app PUBLIC dependency)
 
 if(EXTENSION_DIR)
     target_include_directories(app PRIVATE ${EXTENSION_DIR})

tests/misc/llext-edk/extension/src/main.c

@@ -9,9 +9,14 @@
 
 #include <app_api.h>
 
+#ifndef GLOBAL_OPT
+#define GLOBAL_OPT "MISSING"
+#endif
+
 int start(int bar)
 {
 	printk("foo(%d) is %d\n", bar, foo(bar));
+	printk("GLOBAL_OPT is %s\n", GLOBAL_OPT);
 	return 0;
 }
 EXPORT_SYMBOL(start);

tests/misc/llext-edk/pytest/test_edk.py

@@ -115,6 +115,7 @@ def test_edk(unlaunched_dut: DeviceAdapter):
                 assert "Calling extension from user" in lines
                 assert "foo(42) is 1764" in lines
                 assert "foo(43) is 1849" in lines
+                assert "GLOBAL_OPT is set" in lines
 
             finally:
                 unlaunched_dut.close()