[Buildroot] Question about passing the right TARGET_CC and TARGET_LD to .c and .cpp Makefile in same project

[Arnout Vandecappelle <arnout@mind.be>]

On 02/05/15 18:18, Nils K?hler wrote:
> Hello,
> 
> I have a problem to compile .c and .cpp sources together in one project.
> For .c files everything is fine. but with .cpp i run into problems. It compiles
> witout any error, but will not run on target.
> The executeble itselv is present, but linked against host. I can run the
> executeble on the host but not on the target.
> 
> I have googeled a lot but actually i found no way to solve the problem.
> 
> I monitored two problems to build my .cpp executebles of a project named connect:
> 
>     1. Problem
>         For a multi input file .cpp application the host g++ is used, instead of
> the TARGET_CC, it seems that TARGET_CC is not passed correctly into the makefile
> see below [1. Problem]

 The c++ compiler is TARGET_CXX, not TARGET_CC. So you should also add
CXX=$(TARGET_CXX) in your package.mk file. Or better yet, use
$(TARGET_CONFIGURE_OPTS) which contains everything.

> 
>     2. Problem
>         In case of linking the parts together LD="" Libary path is emty see
> below [2. Problem]
> 
>     The pure .c program the project is compiling fine with right lib and gcc, it
> also runs on the target.
> 
> [Cmmented part output of a make run]
> 
> [1. Problem]
> g++  -Wall -Wextra -m32 -g -rdynamic -pedantic -Wshadow -fbounds-check
> -fstack-protector-all  -c -o util.o util.cpp
> g++  -Wall -Wextra -m32 -g -rdynamic -pedantic -Wshadow -fbounds-check
> -fstack-protector-all  -c -o tally.o tally.cpp
> g++ -Wall -Wextra -m32 -g -rdynamic -pedantic -Wshadow -fbounds-check
> -fstack-protector-all -o tally tally.o util.o
> 
> [2. Problem]
> #    /usr/bin/make -j2
> CXX"/home/koehler/s/br/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-g++"
> LD="" -C /home/koehler/s/br/buildroot/out
> put/build/connect-1.0 tally
> 
> 
> [Normal .c program in same project compiles fine and run on target too]
> #    /usr/bin/make -j2
> CC="/home/koehler/s/br/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-gcc"
> LD="/home/koehler/s/br/buildroot/output/h
> ost/usr/bin/i586-buildroot-linux-uclibc-ld" -C
> /home/koehler/s/br/buildroot/output/build/connect-1.0 gpi_mon

 This output is completely inconsistent with the files you show below: there is
no CXX anywhere below, there is no 'tally' or 'gpi_mon' target being called. If
you ask questions, please try to be as accurate as possible.

> 
> 
> Does anyone have an idear for me how to solve this issue?
> 
> Regards
> 
> NIls
> 
> 
> ----------------------------------------------------------------------------------
> Here are the part of the buildroot makefile I use:
> 
> connect.mk for CONNECT Package:
> 
> define CONNECT_BUILD_CMDS
>     $(MAKE) CC="$(TARGET_CC)" LD="$(TARGET_LD)" -C $(@D) all

 Replace with
	$(TARGET_MAKE_ENV) $(MAKE) $(TARGET_CONFIGURE_OPTS) -C $(@D) \
		tally gpi_mon

(TARGET_MAKE_ENV adds the host utilities to $PATH - not really needed in your
case, but good practice).

 The all target will attempt to build the modules but without
$(LINUX_MAKE_FLAGS), that's bound to give you trouble.

>     $(MAKE) -C $(LINUX_DIR) $(LINUX_MAKE_FLAGS) M=$(@D) modules_install

 This should be in the INSTALL_CMDS; here you should put the same line but with
modules instead of modules_install

> endef
> 
> define CONNECT_INSTALL_TARGET_CMDS
>     $(INSTALL) -D -m 0755 $(@D)/tally $(TARGET_DIR)/bin/tally
>     $(INSTALL) -D -m 0755 $(@D)/gpi_mon $(TARGET_DIR)/bin/gpi_mon
> endef
> 
> define CONNECT_DEVICES
>     /dev/debug  c  666  0  0  42  0  -  -  -
> endef
> 
> $(eval $(generic-package))
> 
> ------------------------------------------------------------------------------------
> 
> 
> And the Makefile for my sourcecode:
> # source makefile
> ccflags-y+=-DUSE_PLATFORM_DEVICE
> ccflags-y+=-Wall -rdynamic -Wshadow -fbounds-check
> 
> # Executebles and objects
> EXEC = gpi_mon tally
> OBJS = tally.o util.o
> 
> #dependencies CPP program
> tally: tally.o util.o
> tally.o: defines.h tally.h tally.cpp
> util.o: defines.h tally.h util.cpp
> 
> #dependencies C program
> gpi_mon.o: defines.h gpi_mon.c
> 
> KERNELDIR ?=
> /home/koehler/s/br/buildroot/output/build/linux-$(BR2_LINUX_KERNEL_VERSION)
> 
> 
> all: modules program
> 
> modules:
>     $(MAKE) -C $(KERNELDIR) M=$$PWD modules
> 
> modules_install:
>     $(MAKE) -C $(KERNELDIR) M=$$PWD modules_install
> 
> program: $(EXEC)
>     $(CC) $(LDFLAGS) -o $@ $(OBJS) $(LDLIBS)

 You're using the C compiler here to link together the C++ object files, does
that work? And you're not even building gpi_mon when doing 'make all'...


 Regards,
 Arnout


> 
> clean:
>     rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions modules.order
> Module.symvers dio *.tmp tally gpi_mon
> 
> ----------------------------------------------------------------------------------------------------
> 
> I use buildroot actual git rep last pull:
> koehler at koehler-laptop-ubuntu-final:~/s/br/buildroot$ git log
> commit 94856075660dab56249fbe3452b34e489c2a79c5
> Author: Peter Korsgaard <peter@korsgaard.com>
> Date:   Mon Apr 27 00:10:53 2015 +0200
> 
> Linux Kernel 3.18.12
> 
> 
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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