cmake: Toolchain abstraction: Introduce toolchain_cc_warning_extended

This is placeholder for extended warning flags, likely to change between
toolchains.

The intent here is to abstract Zephyr's dependence on toolchains,
thus allowing for easier porting to other, perhaps commercial,
toolchains and/or usecases.

No functional change expected.

Signed-off-by: Danny Oerndrup <daor@demant.com>

CMakeLists.txt

@@ -251,6 +251,8 @@ if(W MATCHES "3")
   toolchain_cc_warning_dw_3()
 endif()
 
+# @Intent Add extended, more specific, toolchain warning flags
+toolchain_cc_warning_extended()
 
 # Allow the user to inject options when calling cmake, e.g.
 # 'cmake -DEXTRA_CFLAGS="-Werror -Wno-deprecated-declarations" ..'
@@ -274,29 +276,9 @@ zephyr_compile_options(${COMPILER_OPT_AS_LIST})
 
 # TODO: Include arch compiler options at this point.
 
-if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
-  zephyr_cc_option(
-    #FIXME: need to fix all of those
-    -Wno-sometimes-uninitialized
-    -Wno-shift-overflow
-    -Wno-missing-braces
-    -Wno-self-assign
-    -Wno-address-of-packed-member
-    -Wno-unused-function
-    -Wno-initializer-overrides
-    -Wno-section
-    -Wno-unknown-warning-option
-    -Wno-unused-variable
-    -Wno-format-invalid-specifier
-    -Wno-gnu
-    # comparison of unsigned expression < 0 is always false
-    -Wno-tautological-compare
-    )
-else() # GCC assumed
-  zephyr_cc_option(
-    -Wno-unused-but-set-variable
-    -fno-reorder-functions
-    )
+if(NOT CMAKE_C_COMPILER_ID STREQUAL "Clang")
+  # GCC assumed
+  zephyr_cc_option(-fno-reorder-functions)
 
   if(NOT ${ZEPHYR_TOOLCHAIN_VARIANT} STREQUAL "xcc")
     zephyr_cc_option(-fno-defer-pop)

cmake/compiler/clang/target.cmake

@@ -79,7 +79,7 @@ include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_optimizations.cmake)
 include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_cpp.cmake)
 include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_asm.cmake)
 include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_baremetal.cmake)
-include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_warnings.cmake)
+include(${ZEPHYR_BASE}/cmake/compiler/${COMPILER}/target_warnings.cmake)
 
 macro(toolchain_cc_security_fortify)
   # No op, clang doesn't understand fortify at all

cmake/compiler/clang/target_warnings.cmake

@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: Apache-2.0
+
+# See root CMakeLists.txt for description and expectations of this macro
+
+macro(toolchain_cc_warning_base)
+
+  zephyr_compile_options(
+    -Wall
+    -Wformat
+    -Wformat-security
+    -Wno-format-zero-length
+    -Wno-main
+  )
+
+  zephyr_cc_option(-Wno-pointer-sign)
+
+  # Prohibit void pointer arithmetic. Illegal in C99
+  zephyr_cc_option(-Wpointer-arith)
+
+endmacro()
+
+macro(toolchain_cc_warning_dw_1)
+
+  zephyr_compile_options(
+    -Wextra
+    -Wunused
+    -Wno-unused-parameter
+    -Wmissing-declarations
+    -Wmissing-format-attribute
+    -Wold-style-definition
+    )
+  zephyr_cc_option(
+    -Wmissing-prototypes
+    -Wmissing-include-dirs
+    -Wunused-but-set-variable
+    -Wno-missing-field-initializers
+    )
+
+endmacro()
+
+macro(toolchain_cc_warning_dw_2)
+
+  zephyr_compile_options(
+    -Waggregate-return
+    -Wcast-align
+    -Wdisabled-optimization
+    -Wnested-externs
+    -Wshadow
+    )
+  zephyr_cc_option(
+    -Wlogical-op
+    -Wmissing-field-initializers
+    )
+
+endmacro()
+
+macro(toolchain_cc_warning_dw_3)
+
+  zephyr_compile_options(
+    -Wbad-function-cast
+    -Wcast-qual
+    -Wconversion
+    -Wpacked
+    -Wpadded
+    -Wpointer-arith
+    -Wredundant-decls
+    -Wswitch-default
+    )
+  zephyr_cc_option(
+    -Wpacked-bitfield-compat
+    -Wvla
+    )
+
+endmacro()
+
+macro(toolchain_cc_warning_extended)
+
+  zephyr_cc_option(
+    #FIXME: need to fix all of those
+    -Wno-sometimes-uninitialized
+    -Wno-shift-overflow
+    -Wno-missing-braces
+    -Wno-self-assign
+    -Wno-address-of-packed-member
+    -Wno-unused-function
+    -Wno-initializer-overrides
+    -Wno-section
+    -Wno-unknown-warning-option
+    -Wno-unused-variable
+    -Wno-format-invalid-specifier
+    -Wno-gnu
+    # comparison of unsigned expression < 0 is always false
+    -Wno-tautological-compare
+    )
+
+endmacro()

cmake/compiler/gcc/target_warnings.cmake

@@ -72,3 +72,11 @@ macro(toolchain_cc_warning_dw_3)
     )
 
 endmacro()
+
+macro(toolchain_cc_warning_extended)
+
+  zephyr_cc_option(
+    -Wno-unused-but-set-variable
+    )
+
+endmacro()