4.3. Advanced Rule Files

The previous example on how to create a rule file sometimes works as shown above. But most of the time source archives are not that simple. In this section we want to give the user a more detailed selection how the package will be built.

Adding Static Configure Parameters

The configure scripts of various source archives provide additional parameters to enable or disable features, or to configure them in a specific way.

We assume the configure script of our foo example (refer to section Rule File Creation) supports two additional parameters:

  • –enable-debug: Make the program more noisy. It’s disabled by default.
  • –with-bar: Also build the special executable bar. Building this executable is also disabled by default.

We now want to forward these options to the configure script when it runs in the prepare stage. To do so, we must again open the rule file with our favourite editor and navigate to the prepare stage entry.

PTXdist uses the variable FOO_CONF_OPT as the list of parameters to be given to configure.

Currently this variable is commented out and defined to:

# FOO_CONF_OPT := $(CROSS_AUTOCONF_USR)

The variable CROSS_AUTOCONF_USR is predefined by PTXdist and contains all basic parameters to instruct configure to prepare for a cross compile environment.

To use the two additional mentioned configure parameters, we comment in this line and supplement this expression as follows:

FOO_CONF_OPT := \
    $(CROSS_AUTOCONF_USR) \
    --enable-debug \
    --with-bar

Note

We recommend to use this format with each parameter on a line of its own. This format is easier to read and a diff shows more exactly any change.

To do a fast check if this addition was successful, we run:

$ ptxdist print FOO_CONF_OPT
--prefix=/usr --sysconfdir=/etc --host=arm-v5te-linux-gnueabi --build=i686-host-linux-gnu --enable-debug --with-bar

Note

It depends on the currently selected platform and its architecture what content this variable will have. The content shown above is an example for a target.

Or re-build the package with the new settings:

$ ptxdist drop foo prepare
$ ptxdist targetinstall foo

Adding Dynamic Configure Parameters

Sometimes it makes sense to add this kind of parameters on demand only; especially a parameter like --enable-debug. To let the user decide if this parameter is to be used or not, we must add a menu entry. So, let’s expand our menu. Here is its current content:

## SECTION=project_specific

config FOO
        tristate
        prompt "foo"
        help
          FIXME

We’ll add two menu entries, one for each optional parameter we want to add on demand to the configure parameters:

## SECTION=project_specific

config FOO
       tristate
       prompt "foo"
       help
         FIXME

if FOO
config FOO_DEBUG
       bool
       prompt "add debug noise"

config FOO_BAR
       bool
       prompt "build bar"

endif

Important

Always follow the rule to extend the base name by a suboption name as the trailing part of the variable name. This gives PTXdist the ability to detect a change in the package’s settings (via menuconfig) to force its rebuild on demand.

To make usage of the new menu entries, we must check them in the rule file and add the correct parameters:

#
# autoconf
#
FOO_CONF_OPT := \
    $(CROSS_AUTOCONF_USR) \
    --$(call ptx/endis, PTXCONF_FOO_DEBUG)-debug \
    --$(call ptx/wwo, PTXCONF_FOO_BAR)-bar

Important

Please note the leading PTXCONF_ for each define. While Kconfig is using FOO_BAR, the rule file must use PTXCONF_FOO_BAR instead.

Note

Refer Rule File Macro Reference for further details about these special kind of option macros (e.g. ptx/...).

It is a good practice to always add both settings, e.g. --disable-debug even if this is the default case. Sometimes configure tries to guess something and the binary result might differ depending on the build order. For example some kind of package would also build some X related tools, if X libraries are found. In this case it depends on the build order, if the X related tools are built or not. All the autocheck features are problematic here. So, if we do not want configure to guess its settings we must disable everything we do not want.

To support this process, PTXdist supplies a helper script, located at /path/to/ptxdist/scripts/configure-helper.py that compares the configure output with the settings from FOO_CONF_OPT:

$ /opt/ptxdist-2017.06.0/scripts/configure-helper.py -p libsigrok
--- rules/libsigrok.make
+++ libsigrok-0.5.0
@@ -4,3 +4,74 @@
    --libdir=/usr/lib
    --build=x86_64-host-linux-gnu
    --host=arm-v7a-linux-gnueabihf
+   --enable-warnings=min|max|fatal|no
+   --disable-largefile
+   --enable-all-drivers
+   --enable-agilent-dmm
[...]
+   --enable-ruby
+   --enable-java
+   --without-libserialport
+   --without-libftdi
+   --without-libusb
+   --without-librevisa
+   --without-libgpib
+   --without-libieee1284
+   --with-jni-include-path=DIR-LIST

In this example, many configure options from libsigrok (marked with +) are not yet present in LIBSIGROK_CONF_OPT and must be added, possibly also by providing more dynamic options in the package definition.

If some parts of a package are built on demand only, they must also be installed on demand only. Besides the prepare stage, we also must modify our targetinstall stage:

    @$(call install_copy, foo, 0, 0, 0755, $(FOO_DIR)/foo, /usr/bin/foo)

ifdef PTXCONF_FOO_BAR
    @$(call install_copy, foo, 0, 0, 0755, $(FOO_DIR)/bar, /usr/bin/bar)
endif

    @$(call install_finish, foo)
    @$(call touch)

Now we can play with our new menu entries and check if they are working as expected:

$ ptxdist menuconfig
$ ptxdist targetinstall foo

Whenever we change a FOO related menu entry, PTXdist should detect it and re-build the package when a new build is started.

Managing External Compile Time Dependencies

While running the prepare stage, it could happen that it fails due to a missing external dependency.

For example:

checking whether zlib exists....failed

In this example, our new package depends on the compression library zlib. PTXdist comes with a target zlib. All we need to do in this case is to declare that our new package foo depends on zlib. This kind of dependency is managed in the menu file of our new package by simply adding the select ZLIB line. After this addition our menu file looks like:

## SECTION=project_specific

config FOO
       tristate
       select ZLIB
       prompt "foo"
       help
         FIXME

if FOO
config FOO_DEBUG
       bool
       prompt "add debug noise"

config FOO_BAR
       bool
       prompt "build bar"

endif

PTXdist now builds the zlib first and our new package thereafter.

Refer Controlling Package Dependencies in more Detail for more specific dependency description.

Managing External Compile Time Dependencies on Demand

It is good practice to add only those dependencies that are really required for the current configuration of the package. If the package provides the features foo and bar and its configure provides switches to enable/disable them independently, we can also add dependencies on demand. Let’s assume feature foo needs the compression library libz and bar needs the XML2 library libxml2. These libraries are only required at run-time if the corresponding feature is enabled. To add these dependencies on demand, the menu file looks like:

## SECTION=project_specific

config FOO
       tristate
       select ZLIB if FOO_FOO
       select LIBXML2 if FOO_BAR
       prompt "foo"
       help
         FIXME

if FOO
config FOO_DEBUG
       bool
       prompt "add debug noise"

config FOO_FOO
       bool
       prompt "build foo"

config FOO_BAR
       bool
       prompt "build bar"

endif

Important

Do not add these select statements to the corresponding menu entry. They must belong to the main menu entry of the package to ensure that the calculation of the dependencies between the packages is done in a correct manner.

Managing External Runtime Dependencies

Some packages are building all of their components and also installing them into the target’s sysroot. But only their targetinstall stage decides which parts are copied to the root filesystem. So, compiling and linking of our package will work, because everything required is found in the target’s sysroot.

In our example there is a hidden dependency to the math library libm. Our new package was built successfully, because the linker was able to link our binaries against the libm from the toolchain. But in this case the libm must also be available in the target’s root filesystem to fulfill the run-time dependency: We have to force PTXdist to install libm. libm is part of the glibc package, but is not installed by default (to keep the root filesystem small). So, it does not help to select the GLIBC symbol, to get a libm at run-time.

The correct solution here is to add a select LIBC_M to our menu file. With all the additions above it now looks like:

## SECTION=project_specific

config FOO
       tristate
       select ZLIB if FOO_FOO
       select LIBXML2 if FOO_BAR
       select LIBC_M
       prompt "foo"
       help
         FIXME

if FOO
config FOO_DEBUG
       bool
       prompt "add debug noise"

config FOO_FOO
       bool
       prompt "build foo"

config FOO_BAR
       bool
       prompt "build bar"

endif

Note

There are other packages around, that do not install everything by default. If our new package needs something special, we must take a look into the menu of the other package how to force the required components to be installed and add the corresponding selects to our own menu file. In this case it does not help to enable the required parts in our project configuration, because this has no effect on the build order!

Managing Plain Makefile Packages

Many packages are still coming with a plain Makefile. The user has to adapt it to make it work in a cross compile environment as well. PTXdist can also handle this kind of packages. We only have to specify a special prepare and compile stage.

Such packages often have no special need for any kind of preparation. In this we must instruct PTXdist to do nothing in the prepare stage:

FOO_CONF_TOOL := NO

To compile the package, we can use make’s feature to overwrite variables used in the Makefile. With this feature we can still use the original Makefile but with our own (cross compile) settings.

Most of the time the generic compile rule can be used, only a few settings are required. For a well defined Makefile it is sufficient to set up the correct cross compile environment for the compile stage:

FOO_MAKE_ENV := $(CROSS_ENV)

make will be called in this case with:

$(FOO_MAKE_ENV) $(MAKE) -C $(FOO_DIR) $(FOO_MAKE_OPT)

So, in the rule file only the two variables FOO_MAKE_ENV and FOO_MAKE_OPT must be set, to forward the required settings to the package’s buildsystem. If the package cannot be built in parallel, we can also add the FOO_MAKE_PAR := NO. YES is the default.

Managing CMake/QMake/Meson Packages

Building packages that use cmake, qmake or meson is much like building packages with an autotools based buildsystem. We need to specify the configuration tool:

FOO_CONF_TOOL := cmake

or

FOO_CONF_TOOL := qmake

or respectively

FOO_CONF_TOOL := meson

And provide the correct configuration options. The syntax is different so PTXdist provides additional macros to simplify configurable features. For cmake the configuration options typically look like this:

FOO_CONF_OPT := \
    $(CROSS_CMAKE_USR) \
    -DBUILD_TESTS:BOOL=OFF \
    -DENABLE_BAR:BOOL=$(call ptx/onoff, PTXCONF_FOO_BAR)

For qmake the configuration options typically look like this:

FOO_CONF_OPT := \
    $(CROSS_QMAKE_OPT) \
    PREFIX=/usr

And for meson the configuration options typically look like this:

FOO_CONF_OPT := \
    $(CROSS_MESON_USR) \
    -Dbar=$(call ptx/truefalse,PTXCONF_FOO_BAR)

Please note that currently only host and target cmake/meson packages and only target qmake packages are supported.

Managing Python Packages

As with any other package, the correct configuration tool must be selected for Python packages:

FOO_CONF_TOOL := python

Note

For Python3 packages the value must be python3.

No Makefiles are used when building Python packages so the usual make and make install for the compile and install stages cannot be used. PTXdist will call python setup.py build and python setup.py install instead.

Note

FOO is still the name of our example package. It must be replaced by the real package name.