From 3829cb5c41b8fcc3ab1aca2ba61771508cd560df Mon Sep 17 00:00:00 2001
From: Daniel Leung <daniel.leung@intel.com>
Date: Thu, 1 Nov 2018 09:45:54 -0700
Subject: [PATCH] cmake: parameterized flags to not include standard
 defines/files

Not all compiles/linkers support the GCC flags to not include standard
defines, include files and libraries. So make these parameters such
that the toolchain can define them when supported.

Also, according to documentation, -nostdlib does the same for both
-nostartfiles and -nodefaultlibs. So remove the redundant ones.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
---
 CMakeLists.txt            | 4 +---
 cmake/compiler/gcc.cmake  | 6 ++++++
 cmake/compiler/llvm.cmake | 7 ++++++-
 cmake/dts.cmake           | 3 ++-
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ccff722a319..a282b51163b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -165,8 +165,6 @@ endif()
 
 if(NOT CONFIG_NATIVE_APPLICATION)
 zephyr_ld_options(
-  -nostartfiles
-  -nodefaultlibs
   -nostdlib
   -static
   -no-pie
@@ -748,7 +746,7 @@ function(construct_add_custom_command_for_linker_pass linker_output_name output_
     COMMAND ${CMAKE_C_COMPILER}
     -x assembler-with-cpp
     ${NOSTDINC_F}
-    -undef
+    ${NOSYSDEF_CFLAG}
     -MD -MF ${linker_cmd_file_name}.dep -MT ${BASE_NAME}/${linker_cmd_file_name}
     ${ZEPHYR_INCLUDES}
     ${LINKER_SCRIPT_DEFINES}
diff --git a/cmake/compiler/gcc.cmake b/cmake/compiler/gcc.cmake
index a8b58088873..79f7a7b7ce0 100644
--- a/cmake/compiler/gcc.cmake
+++ b/cmake/compiler/gcc.cmake
@@ -53,6 +53,12 @@ find_program(CMAKE_CXX_COMPILER ${cplusplus_compiler} PATH ${TOOLCHAIN_HOME} NO_
 
 set(NOSTDINC "")
 
+# Note that NOSYSDEF_CFLAG may be an empty string, and
+# set_ifndef() does not work with empty string.
+if(NOT DEFINED NOSYSDEF_CFLAG)
+  set(NOSYSDEF_CFLAG -undef)
+endif()
+
 foreach(file_name include include-fixed)
   execute_process(
     COMMAND ${CMAKE_C_COMPILER} --print-file-name=${file_name}
diff --git a/cmake/compiler/llvm.cmake b/cmake/compiler/llvm.cmake
index 5548353f9bc..d43dbdfa1b7 100644
--- a/cmake/compiler/llvm.cmake
+++ b/cmake/compiler/llvm.cmake
@@ -3,6 +3,12 @@
 
 set(NOSTDINC "")
 
+# Note that NOSYSDEF_CFLAG may be an empty string, and
+# set_ifndef() does not work with empty string.
+if(NOT DEFINED NOSYSDEF_CFLAG)
+  set(NOSYSDEF_CFLAG -undef)
+endif()
+
 foreach(file_name include include-fixed)
   execute_process(
     COMMAND ${CMAKE_C_COMPILER} --print-file-name=${file_name}
@@ -19,4 +25,3 @@ endforeach()
 
 set(CMAKE_REQUIRED_FLAGS -nostartfiles -nostdlib ${isystem_include_flags} -Wl,--unresolved-symbols=ignore-in-object-files)
 string(REPLACE ";" " " CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
-
diff --git a/cmake/dts.cmake b/cmake/dts.cmake
index 2ae55dfe59a..429ea91377a 100644
--- a/cmake/dts.cmake
+++ b/cmake/dts.cmake
@@ -92,7 +92,8 @@ if(CONFIG_HAS_DTS)
     -include ${AUTOCONF_H}
     ${DTC_INCLUDE_FLAG_FOR_DTS}  # include the DTS source and overlays
     -I${ZEPHYR_BASE}/dts/common
-    -undef -D__DTS__
+    ${NOSYSDEF_CFLAG}
+    -D__DTS__
     -P
     -E ${ZEPHYR_BASE}/misc/empty_file.c
     -o ${BOARD}.dts.pre.tmp