%poky; ] > You can use the SDK toolchain directly with Makefile, Autotools, and Eclipse-based projects. This chapter covers the first two, while the "Developing Applications Using Eclipse" Chapter covers the latter.

Once you have a suitable cross-development toolchain installed, it is very easy to develop a project outside of the OpenEmbedded build system. This section presents a simple "Helloworld" example that shows how to set up, compile, and run the project.

Follow these steps to create a simple GNU Autotools-based project: Create Your Directory: Create a clean directory for your project and then make that directory your working location: $ mkdir $HOME/helloworld $ cd $HOME/helloworld Populate the Directory: Create hello.c, Makefile.am, and configure.ac files as follows: For hello.c, include these lines: #include <stdio.h> main() { printf("Hello World!\n"); } For Makefile.am, include these lines: bin_PROGRAMS = hello hello_SOURCES = hello.c For configure.ac, include these lines: AC_INIT(hello,0.1) AM_INIT_AUTOMAKE([foreign]) AC_PROG_CC AC_PROG_INSTALL AC_OUTPUT(Makefile) Source the Cross-Toolchain Environment Setup File: As described earlier in the manual, installing the cross-toolchain creates a cross-toolchain environment setup script in the directory that the SDK was installed. Before you can use the tools to develop your project, you must source this setup script. The script begins with the string "environment-setup" and contains the machine architecture, which is followed by the string "poky-linux". Here is an example that sources a script from the default SDK installation directory that uses the 32-bit Intel x86 Architecture and the &DISTRO_NAME; Yocto Project release: $ source /opt/poky/&DISTRO;/environment-setup-i586-poky-linux Generate the Local aclocal.m4 Files and Create the configure Script: The following GNU Autotools generate the local aclocal.m4 files and create the configure script: $ aclocal $ autoconf Generate Files Needed by GNU Coding Standards: GNU coding standards require certain files in order for the project to be compliant. This command creates those files: $ touch NEWS README AUTHORS ChangeLog Generate the Configure File: This command generates the configure: $ automake -a Cross-Compile the Project: This command compiles the project using the cross-compiler. The CONFIGURE_FLAGS environment variable provides the minimal arguments for GNU configure: $ ./configure ${CONFIGURE_FLAGS} Make and Install the Project: These two commands generate and install the project into the destination directory: $ make $ make install DESTDIR=./tmp Verify the Installation: This command is a simple way to verify the installation of your project. Running the command prints the architecture on which the binary file can run. This architecture should be the same architecture that the installed cross-toolchain supports. $ file ./tmp/usr/local/bin/hello Execute Your Project: To execute the project in the shell, simply enter the name. You could also copy the binary to the actual target hardware and run the project there as well: $ ./hello As expected, the project displays the "Hello World!" message.

For an Autotools-based project, you can use the cross-toolchain by just passing the appropriate host option to configure.sh. The host option you use is derived from the name of the environment setup script found in the directory in which you installed the cross-toolchain. For example, the host option for an ARM-based target that uses the GNU EABI is armv5te-poky-linux-gnueabi. You will notice that the name of the script is environment-setup-armv5te-poky-linux-gnueabi. Thus, the following command works to update your project and rebuild it using the appropriate cross-toolchain tools: $ ./configure --host=armv5te-poky-linux-gnueabi \ --with-libtool-sysroot=sysroot_dir If the configure script results in problems recognizing the --with-libtool-sysroot=sysroot-dir option, regenerate the script to enable the support by doing the following and then run the script again: $ libtoolize --automake $ aclocal -I ${OECORE_TARGET_SYSROOT}/usr/share/aclocal [-I dir_containing_your_project-specific_m4_macros] $ autoconf $ autoheader $ automake -a

For Makefile-based projects, the cross-toolchain environment variables established by running the cross-toolchain environment setup script are subject to general make rules. To illustrate this, consider the following four cross-toolchain environment variables: CC=i586-poky-linux-gcc -m32 -march=i586 --sysroot=/opt/poky/&DISTRO;/sysroots/i586-poky-linux LD=i586-poky-linux-ld --sysroot=/opt/poky/&DISTRO;/sysroots/i586-poky-linux CFLAGS=-O2 -pipe -g -feliminate-unused-debug-types CXXFLAGS=-O2 -pipe -g -feliminate-unused-debug-types Now, consider the following three cases: Case 1 - No Variables Set in the Makefile: Because these variables are not specifically set in the Makefile, the variables retain their values based on the environment. Case 2 - Variables Set in the Makefile: Specifically setting variables in the Makefile during the build results in the environment settings of the variables being overwritten. Case 3 - Variables Set when the Makefile is Executed from the Command Line: Executing the Makefile from the command-line results in the variables being overwritten with command-line content regardless of what is being set in the Makefile. In this case, environment variables are not considered unless you use the "-e" flag during the build: $ make -e file If you use this flag, then the environment values of the variables override any variables specifically set in the Makefile. For information on the variables set up by the cross-toolchain environment setup script, see the "Running the Extensible SDK Environment Setup Script" section.