[nrfconnect] Do not link libCHIPShell.a with --whole-archive

libCHIPShell.a is already part of libCHIP.a but the former
had to be linked additionally with --whole-archive flag to
process the shell and init objects defined with SHELL_XXX
and SYS_INIT Zephyr macros and, in turn, register Matter
shell commands properly.

This symbol duplication between the two libraries causes
issues when building Matter with LTO, so replace the current
approach with explicitly pulling in one symbol from
MainLoopZephyr.cpp file.

Signed-off-by: Damian Krolik <damian.krolik@nordicsemi.no>

config/nrfconnect/chip-module/CMakeLists.txt

@@ -200,7 +200,6 @@ matter_generate_args_tmp_file()
 # ==============================================================================
 
 matter_build(chip
-    LIB_SHELL   ${CONFIG_CHIP_LIB_SHELL}
     LIB_TESTS   ${CONFIG_CHIP_BUILD_TESTS}
     DEVICE_INFO_EXAMPLE_PROVIDER ${CONFIG_CHIP_EXAMPLE_DEVICE_INFO_PROVIDER}
     GN_DEPENDENCIES kernel
@@ -225,6 +224,16 @@ if (CONFIG_CHIP_MALLOC_SYS_HEAP_OVERRIDE)
     )
 endif()
 
+if (CONFIG_CHIP_LIB_SHELL)
+    # Force pulling chip::Shell::Engine::RunMainLoop() in the final binary.
+    # Without this workaround, the linker script does not process the shell and
+    # init objects defined in MainLoopZephyr.cpp unless the Matter library or
+    # the Matter shell library is linked using the '--whole-archive' flag.
+    target_link_options(chip INTERFACE
+        -Wl,-u,_ZN4chip5Shell6Engine11RunMainLoopEv
+    )
+endif()
+
 # ==============================================================================
 # Define 'chip-ota-image' target for building CHIP OTA image
 # ==============================================================================

src/lib/shell/MainLoopZephyr.cpp

@@ -91,15 +91,15 @@ int ExecCommandInShellThread(const struct shell * shell, size_t argc, char ** ar
     return error == CHIP_NO_ERROR ? 0 : -ENOEXEC;
 }
 
-int RegisterCommands()
+int RegisterMatterCommands()
 {
     Shell::Engine::Root().RegisterDefaultCommands();
     return 0;
 }
 
 } // namespace
 
-SYS_INIT(RegisterCommands, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
+SYS_INIT(RegisterMatterCommands, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
 SHELL_CMD_ARG_REGISTER(matter, NULL, "Matter commands", ExecCommandInShellThread, 1, CHIP_SHELL_MAX_TOKENS);
 
 namespace chip {

src/platform/Zephyr/SysHeapMalloc.cpp

@@ -64,7 +64,7 @@ LockGuard::~LockGuard()
     }
 }
 
-int initHeap()
+int InitSysHeapMalloc()
 {
     sys_heap_init(&sHeap, sHeapMemory, sizeof(sHeapMemory));
     return 0;
@@ -74,7 +74,7 @@ int initHeap()
 
 // Initialize the heap in the POST_KERNEL phase to make sure that it is ready even before
 // C++ static constructors are called (which happens prior to the APPLICATION initialization phase).
-SYS_INIT(initHeap, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
+SYS_INIT(InitSysHeapMalloc, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
 
 namespace chip {
 namespace DeviceLayer {