##############################################
# OpenWrt Makefile for helloworld program
#
#
# Most of the variables used here are defined in
# the include directives below. We just need to
# specify a basic description of the package,
# where to build our program, where to find
# the source files, and where to install the
# compiled program on the router.
#
# Be very careful of spacing in this file.
# Indents should be tabs, not spaces, and
# there should be no trailing whitespace in
# lines that are not commented.
#
##############################################

include $(TOPDIR)/rules.mk

# Name and release number of this package
PKG_NAME:=helloworld
PKG_RELEASE:=1

# This specifies the directory where we're going to build the program.
# The root build directory, $(BUILD_DIR), is by default the build_mipsel
# directory in your OpenWrt SDK directory
PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)

include $(INCLUDE_DIR)/package.mk

# Specify package information for this program.
# The variables defined here should be self explanatory.
define Package/helloworld
    SECTION:=utils
    CATEGORY:=Utilities
    TITLE:=helloworld -- prints a snarky message
endef

define Package/helloworld/description
    If you can't figure out what this program does,
    you're probably brain-dead and need immediate
    medical attention.
endef

define Package/helloworld/conffiles
endef

# Specify what needs to be done to prepare for building the package.
# In our case, we need to copy the source files to the build directory.
# This is NOT the default.  The default uses the PKG_SOURCE_URL and the
# PKG_SOURCE which is not defined here to download the source from the web.
# In order to just build a simple program that we have just written, it is
# much easier to do it this way.
define Build/Prepare
    mkdir -p $(PKG_BUILD_DIR)
    $(CP) ./src/* $(PKG_BUILD_DIR)/
endef

#########################################################################################
# The Build/Compile directive needs to be specified in order to customize compilation
# and linking of our program.  We need to link to uClibc++ and to specify that we
# do NOT want to link to the standard template library.
#
# To do this we define the LIBS variable.  To prevent linking to the standard libraries we
# add "-nodefaultlibs" to the $(LIBS) variable and then specify "-lgcc -lc" to ensure that
# there are no unresolved references to internal GCC library subroutines. Finally
# "-luClibc++" to link to the  uClibc++ library.  Also, we need to specify "-nostdinc++"
# in the compiler flags to tell the compiler that c++ standard template library functions
# and data structures will be linked to in specified external libraries and not the
# standard libraries.
#########################################################################################
define Build/Compile
    $(MAKE) -C $(PKG_BUILD_DIR) \
        LIBS="-nodefaultlibs -lgcc -lc -luClibc++" \
        LDFLAGS="$(EXTRA_LDFLAGS)" \
        CXXFLAGS="$(TARGET_CFLAGS) $(EXTRA_CPPFLAGS) -nostdinc++" \
        $(TARGET_CONFIGURE_OPTS) \
        CROSS="$(TARGET_CROSS)" \
        ARCH="$(ARCH)" \
        $(1);
endef

# Specify where and how to install the program. Since we only have one file,
# the helloworld executable, install it by copying it to the /bin directory on
# the router. The $(1) variable represents the root directory on the router running
# OpenWrt. The $(INSTALL_DIR) variable contains a command to prepare the install
# directory if it does not already exist.  Likewise $(INSTALL_BIN) contains the
# command to copy the binary file from its current location (in our case the build
# directory) to the install directory.
define Package/helloworld/install
    $(INSTALL_DIR) $(1)/bin
    $(INSTALL_BIN) $(PKG_BUILD_DIR)/helloworld $(1)/bin/
endef

#define Build/InstallDev
#endif

# This line executes the necessary commands to compile our program.
# The above define directives specify all the information needed, but this
# line calls BuildPackage which in turn actually uses this information to
# build a package.
$(eval $(call BuildPackage,helloworld))

# Make file
helloworld: helloworld.o
    $(CXX) $(LDFLAGS) helloworld.o -o helloworld $(LIBS)

helloworld.o: helloworld.cpp
    $(CXX) $(CXXFLAGS) -c helloworld.cpp

clean:
    rm *.o helloworld

/****************
* Helloworld.cpp
*****************/
#include <iostream>
#include <string>

using namespace std;

int main()
{
    string s = "Hell! O' world, why won't my c++ code run?\n\n";
    cout << s;
    return 0;
}

#include <iostream.h>
#include <string.h>