How to stop CMake appending C compiler flags - makefile

Question

I converted an old style makefile to a CMake CMakeLists.txt file so that I can load a project into JetBrain's new CLion IDE.
I thought it would be easy, but I'm stuck at the point of CMake appending some custom compiler flags to the compilation command which cause a compilation error. I don't have enough knowledge of CMake to solve this issue.
Here is the original makefile.
# makefile
# Main Filename to be compiled
MAINFILE = TestProgram
# Paths
DRIVE := C:
COMPILERROOT := $(DRIVE)/GNUHC11
COMPILERPATH := $(COMPILERROOT)/bin
GELROOT := $(DRIVE)/library/gel-hc1x-1.6.1
GELINCLUDESDIR := $(GELROOT)/include
# Compiler, Linker, Object Copy, and Object Dump path
CC := $(COMPILERPATH)/m6811-elf-gcc # compiler
OC := $(COMPILERPATH)/m6811-elf-objcopy # object copy
OD := $(COMPILERPATH)/m6811-elf-objdump # object dump
# Includes
GELINCLUDES += -I$(GELINCLUDESDIR) -I$(GELINCLUDESDIR)/asm-m68hc11/arch-32k
# Compiler Flags
CFLAGS += -Os # turn on optimizer
CFLAGS += -mshort # consider type int to be 16 bits
CFLAGS += -Wl,-m,m68hc11elfb # build for elf file and use memory.x for memory map
CFLAGS += -I. $(GELINCLUDES) # Add current dir and gel library for includes
CFLAGS += -Dmc6811 # Add define to define the processor architecture for gel includes
# C Source codes to be compiled
SRC1 = $(MAINFILE).c
SRC2 = Interrupts.c
SRC3 = Utilities.c
# C Header files dependencies
HDR1 = $(MAINFILE).h
HDR2 = Interrupts.h
HDR3 = Utilities.h
SRCS = $(SRC1) $(SRC2) $(SRC3)
HDRS = $(HDR1) $(HDR2) $(HDR3)
# Elf file to be generated
ELF1 = $(SRC1:.c=.elf)
# Generate Bin file for programming & Assembly dump
$(MAINFILE).bin : $(ELF1)
$(OC) -O binary $(ELF1) $(MAINFILE).bin
$(OD) -xDC --section=.text --section=.vectors $(ELF1) >$(MAINFILE).dump
# Full compile and link
$(ELF1) : $(SRCS) $(HDRS)
$(CC) $(CFLAGS) -o $(ELF1) $(SRCS)
clean ::
del *.dump
del *.elf
del *.bin
And here is my attempt at the CMakeLists.txt file.
cmake_minimum_required(VERSION 2.8.4)
# program names
set(HC11C m6811-elf-gcc.exe)
set(OBJCOPY m6811-elf-objcopy.exe)
set(OBJDUMP m6811-elf-objdump.exe)
# Important project paths
set(LIB_INC_PATH "C:/library/gel-hc1x-1.6.1/include"
"C:/library/gel-hc1x-1.6.1/include/asm-m68hc11/arch-32k")
set(HC11C_PATH "C:/GNUHC11/bin")
# Sets the compiler
# Needs to come before the project function
set(CMAKE_SYSTEM_NAME Generic)
set(CMAKE_C_COMPILER "${HC11C_PATH}/${HC11C}")
set(MAIN_FILE "TestProgram")
project(${MAIN_FILE})
# Files to be compiled
set(BASE_PATH "${${PROJECT_NAME}_SOURCE_DIR}")
set(INC_PATH "${BASE_PATH}")
set(SRC_PATH "${BASE_PATH}")
set(SRC_FILES "${SRC_PATH}/${MAIN_FILE}.c"
"${SRC_PATH}/Interrupts.c"
"${SRC_PATH}/Utilities.c")
# Attempt to clear the other spurious compiler flags that I don't want,
# and which cause a compiler arguments error.
# This doesn't seem to work - the defaults still appear.
set(CMAKE_C_FLAGS_DEBUG "")
set(CMAKE_C_FLAGS_RELEASE "")
set(CMAKE_C_FLAGS_RELWITHDEBINFO "")
set(CMAKE_C_FLAGS_MINSIZEREL "")
# Compiler flags
set(CWARN "-Wl,-m,m68hc11elfb") # build for elf file and use memory.x for memory map
set(CTUNING "-mshort") # consider type int to be 16 bits
set(COPT "-Os") # turn on optimizer
set(CDEFS "-Dmc6811") # Add define to define the processor architecture for gel includes
set(CFILES "${MAIN_FILE}.c Interrupts.c Utilities.c")
set(CFLAGS "${CDEFS} ${COPT} ${CWARN} ${CTUNING} ${CFILES}")
set(CMAKE_C_FLAGS "${CFLAGS}")
# Project setup
include_directories(${INC_PATH} ${LIB_INC_PATH})
add_executable(${MAIN_FILE} ${SRC_FILES})
set_target_properties(${MAIN_FILE} PROPERTIES OUTPUT_NAME "${MAIN_FILE}.elf")
# Compiling targets
add_custom_target(main ALL ${OBJCOPY} -O binary "${MAIN_FILE}.elf" "${MAIN_FILE}.bin" DEPENDS ${MAIN_FILE})
add_custom_target(dump ALL ${OBJDUMP} -xDC --section=.text --section=.vectors "${MAIN_FILE}.elf" > "${MAIN_FILE}.dump" DEPENDS main)
set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES "${MAIN_FILE}.dump;${MAIN_FILE}.elf;${MAIN_FILE}.bin")
# Config logging
message("* ")
message("* Project Name:\t${PROJECT_NAME}")
message("* Project Source:\t${SRC_PATH}")
message("* Project Include:\t${INC_PATH}")
message("* Library Include:\t${LIB_INC_PATH}")
message("* ")
message("* Project Source Files:\t${SRC_FILES}")
message("* MAIN_FILE variable:\t${MAIN_FILE}")
message("* ")
message("* C Flags:\t${CMAKE_C_FLAGS}")
message("* ")
Here is the generated compilation command:
C:\GNUHC11\bin\m6811-elf-gcc.exe "-xc" "-Dmc6811" "-Os" "-Wl,-m,m68hc11elfb" "-mshort" "TestProgram.c" "Interrupts.c" "Utilities.c" "-IC:\\DEVELO~1\\source" "-IC:\\library\\gel-hc1x-1.6.1\\include" "-IC:\\library\\gel-hc1x-1.6.1\\include\\asm-m68hc11\\arch-32k" "-v" "-dD" "-E" "-D___CIDR_IGNORE_DEFINITIONS_START"
It would work but for the auto appended "-E" compiler flag at the end which I don't want. The other appended flags "-v" "-dD" and '-D___CIDR..." are also unwanted but do not cause a compilation error like "-E" does. How can I turn these appended flags off?
Thanks in advance for any help.

Answer 1

It seems you are cross-compiling, so the preferred cmake configuration is a bit different than normal.
See http://www.vtk.org/Wiki/CMake_Cross_Compiling for details, pay attention to the "toolchain file".
I have no idea regarding the auto-appended flags.
You can also have a look at the generated CMakeCache.txt file, either with any editor, from CLion itself, or with cmake-gui.
Remember that CLion copies your CMakeLists.txt in a funky temporary directory and runs cmake off the temporary directory, if you want to look at CMakeCache.txt by hand.
What I suggest is to put aside CLion while you are debugging the CMakeLists.txt, and just use cmake or cmake-gui directly from the shell.
Don't give up, both cmake and CLion are two very good programs IMHO :-)

Answer 2

There doesn't seem to be too much information on this one, but I also ran into this issue. In cmake if you do something like
target_compile_options(game PRIVATE /W4 /WX /wd4100 /wd4200 /wd4201 /FAs /EHsc /Gh /GH)
this will add those options for all compilers in that target.
You can use a generator if you want to add language specific options, so I changed it to:
target_compile_options(game PRIVATE
$<$<COMPILE_LANGUAGE:C>:/W4 /WX /wd4100 /wd4200 /wd4201 /FAs /EHsc /Gh /GH>)
which works.