Compiling FreeRTOS with GCC, app code with G++ - c++

Question

I've got a Stellaris Launchpad board with a Cortex M4F on it. I want to use FreeRTOS on the board with some of my own C++ code. FreeRTOS, however, is written in C so will not compile with G++; I've tried.
I read somewhere that I should compile FreeRTOS with gcc, then compile my application code with g++, then pull them together using the linker. This makes sense, but I'm really struggling with how to put this behaviour down in a Makefile. I found this Makefile which just confused me more.
Currently, I'm just using the Makefile distributed with the FreeRTOS example in the Stellaris demos, but that's set up for C code only. This question is asking something similar to what I'm after, but I can't wrap my head around how to compile FreeRTOS with GCC and the rest of my code with G++.
FreeRTOS apparently wraps it's code in extern "C" { } directives but attempting using G++ still fails when compiling the FreeRTOS codebase.
I don't like posting large amounts of code on SO, but the more information the better I suppose. The Stellaris demos have a common makedefs file:
# Get the operating system name. If this is Cygwin, the .d files will be
# munged to convert c: into /cygdrive/c so that "make" will be happy with the
# auto-generated dependencies.
os:=${shell uname -s}
# The compiler to be used.
ifndef COMPILER
COMPILER=gcc
endif
# Definitions for using GCC.
ifeq (${COMPILER}, g++)
# Get the prefix for the tools to use. Use arm-stellaris-eabi if it exists,
# otherwise fall back to arm-none-eabi.
PREFIX=${shell type arm-stellaris-eabi-gcc > /dev/null 2>&1 && \
echo arm-stellaris-eabi || echo arm-none-eabi}
# The command for calling the compiler.
CC=${PREFIX}-${COMPILER}
# The location of the C compiler
# ARMGCC_ROOT is used by some makefiles that need to know where the compiler
# is installed. It is not used further for normal stellarisware apps
ARMGCC_ROOT:=${shell dirname '${shell sh -c "which ${CC}"}'}/..
# Determine the compiler CPU/FPU options based on the processor variant.
ifndef VARIANT
CPU=-mcpu=cortex-m3
FPU=
else
ifeq (${VARIANT}, cm3)
CPU=-mcpu=cortex-m3
FPU=
else
ifeq (${VARIANT}, cm4f)
CPU=-mcpu=cortex-m4
FPU=-mfpu=fpv4-sp-d16 -mfloat-abi=softfp
else
$(error Unknown processor variant ${VARIANT}!)
endif
endif
endif
# The flags passed to the assembler.
AFLAGS=-mthumb \
${CPU} \
${FPU} \
-MD
# The flags passed to the compiler.
CFLAGS=-mthumb \
${CPU} \
${FPU} \
-Os \
-ffunction-sections \
-fdata-sections \
-MD \
-Wall \
-pedantic \
-DPART_${PART} \
-c
# The command for calling the library archiver.
AR=${PREFIX}-ar
# The command for calling the linker.
LD=${PREFIX}-ld
# The flags passed to the linker.
LDFLAGS=--gc-sections
# Get the location of libgcc.a from the GCC front-end.
LIBGCC=${shell ${CC} ${CFLAGS} -print-libgcc-file-name}
# Get the location of libc.a from the GCC front-end.
LIBC=${shell ${CC} ${CFLAGS} -print-file-name=libc.a}
# Get the location of libm.a from the GCC front-end.
LIBM=${shell ${CC} ${CFLAGS} -print-file-name=libm.a}
# The command for extracting images from the linked executables.
OBJCOPY=${PREFIX}-objcopy
# Tell the compiler to include debugging information if the DEBUG environment
# variable is set.
ifdef DEBUG
CFLAGS+=-g -D DEBUG
endif
# Add the tool specific CFLAGS.
CFLAGS+=${CFLAGSgcc}
# Add the include file paths to AFLAGS and CFLAGS.
AFLAGS+=${patsubst %,-I%,${subst :, ,${IPATH}}}
CFLAGS+=${patsubst %,-I%,${subst :, ,${IPATH}}}
# The rule for building the object file from each C source file.
${COMPILER}${SUFFIX}/%.o: %.c
#if [ 'x${VERBOSE}' = x ]; \
then \
echo " CC ${<}"; \
else \
echo ${CC} ${CFLAGS} -D${COMPILER} -o ${#} ${<}; \
fi
#${CC} ${CFLAGS} -D${COMPILER} -o ${#} ${<}
ifneq ($(findstring CYGWIN, ${os}), )
#sed -i -r 's/ ([A-Za-z]):/ \/cygdrive\/\1/g' ${#:.o=.d}
endif
# The rule for building the object file from each assembly source file.
${COMPILER}${SUFFIX}/%.o: %.S
#if [ 'x${VERBOSE}' = x ]; \
then \
echo " AS ${<}"; \
else \
echo ${CC} ${AFLAGS} -D${COMPILER} -o ${#} -c ${<}; \
fi
#${CC} ${AFLAGS} -D${COMPILER} -o ${#} -c ${<}
ifneq ($(findstring CYGWIN, ${os}), )
#sed -i -r 's/ ([A-Za-z]):/ \/cygdrive\/\1/g' ${#:.o=.d}
endif
# The rule for creating an object library.
${COMPILER}${SUFFIX}/%.a:
#if [ 'x${VERBOSE}' = x ]; \
then \
echo " AR ${#}"; \
else \
echo ${AR} -cr ${#} ${^}; \
fi
#${AR} -cr ${#} ${^}
# The rule for linking the application.
${COMPILER}${SUFFIX}/%.axf:
#if [ 'x${SCATTERgcc_${notdir ${#:.axf=}}}' = x ]; \
then \
ldname="${ROOT}/${COMPILER}/standalone.ld"; \
else \
ldname="${SCATTERgcc_${notdir ${#:.axf=}}}"; \
fi; \
if [ 'x${VERBOSE}' = x ]; \
then \
echo " LD ${#} ${LNK_SCP}"; \
else \
echo ${LD} -T $${ldname} \
--entry ${ENTRY_${notdir ${#:.axf=}}} \
${LDFLAGSgcc_${notdir ${#:.axf=}}} \
${LDFLAGS} -o ${#} $(filter %.o %.a, ${^}) \
'${LIBM}' '${LIBC}' '${LIBGCC}'; \
fi; \
${LD} -T $${ldname} \
--entry ${ENTRY_${notdir ${#:.axf=}}} \
${LDFLAGSgcc_${notdir ${#:.axf=}}} \
${LDFLAGS} -o ${#} $(filter %.o %.a, ${^}) \
'${LIBM}' '${LIBC}' '${LIBGCC}'
#${OBJCOPY} -O binary ${#} ${#:.axf=.bin}
endif
The above file is included by the Makefile itself (below):
# Defines the part type that this project uses.
PART=LM4F120H5QR
# Set the processor variant.
VARIANT=cm4f
# The base directory for StellarisWare.
ROOT=../lib
COMPILER=gcc
# Include the common make definitions.
include ${ROOT}/makedefs
# Where to find source files that do not live in this directory.
VPATH=${ROOT}/FreeRTOS/Source/portable/GCC/ARM_CM4F
VPATH+=${ROOT}/FreeRTOS/Source/portable/MemMang/
VPATH+=${ROOT}/FreeRTOS/Source
VPATH+=${ROOT}/drivers
VPATH+=${ROOT}/utils
# Where to find header files that do not live in the source directory.
IPATH=.
IPATH+=..
IPATH+=${ROOT}
IPATH+=${ROOT}/FreeRTOS/Source/portable/GCC/ARM_CM4F
IPATH+=${ROOT}/FreeRTOS
IPATH+=${ROOT}/FreeRTOS/Source/include
IPATH+=${ROOT}
# The default rule, which causes the FreeRTOS example to be built.
all: ${COMPILER}
all: ${COMPILER}/freertos_demo.axf
# The rule to clean out all the build products.
clean:
#rm -rf ${COMPILER} ${wildcard *~}
# The rule to create the target directory.
${COMPILER}:
#mkdir -p ${COMPILER}
# Rules for building the FreeRTOS example.
${COMPILER}/freertos_demo.axf: ${COMPILER}/buttons.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/freertos_demo.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/heap_2.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/led_task.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/list.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/port.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/queue.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/rgb.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/startup_${COMPILER}.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/switch_task.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/tasks.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/uartstdio.o
${COMPILER}/freertos_demo.axf: ${COMPILER}/ustdlib.o
${COMPILER}/freertos_demo.axf: ${ROOT}/driverlib/${COMPILER}-cm4f/libdriver-cm4f.a
${COMPILER}/freertos_demo.axf: freertos_demo.ld
SCATTERgcc_freertos_demo=freertos_demo.ld
ENTRY_freertos_demo=ResetISR
CFLAGSgcc=-DTARGET_IS_BLIZZARD_RA1
# Include the automatically generated dependency files.
ifneq (${MAKECMDGOALS},clean)
-include ${wildcard ${COMPILER}/*.d} __dummy__
endif
Some of my directory structure is as follows:
Projects/
lib/
FreeRTOS/
driverlib/
drivers/
inc/
utils/
makedefs
TestProject/
loads.cpp
of.cpp
files.h
here.h
Makefile
If I'm correct in saying that FreeRTOS must be compiled with GCC, then linked with my C++ project code, how can I modify my current Makefile to do that? I want a reasonably generic solution so I can re-use it in other projects, but I don't know much about the C/C++ build process or Makefiles, hence me asking this (lengthy) question. I don't want/mean to sound like I'm asking a "do this for me" question, but I really cannot work out how to do this despite searching on Google and on SO.

Answer 1

I don't use FreeRTOS with C++ myself, but it has been discussed many times on the FreeRTOS forum and there are a few C++ frameworks in the FreeRTOS Interactive site.