termux-packages/docs/BUILD.md

Build Documentation

This document is intended to describe how to build a package.

Flow of a Build

Basics

1. Sets up a patched stand-alone Android NDK toolchain if necessary.

2. Reads packages/$PKG/build.sh to find out where to find the source code of the package and how to build it.

3. Extracts the source in $HOME/.termux-build/$PKG/src.

4. Applies all patches in packages/$PKG/*.patch.

5. Builds the package under $HOME/.termux-build/$PKG/ (either in the build/ directory there or in the src/ directory if the package is specified to build in the src dir) and installs it to $PREFIX.

6. Extracts modified files in $PREFIX into $HOME/.termux-build/$PKG/massage and massages the files there for distribution (removes some files, splits it up in sub-packages, modifies elf files).

7. Creates a deb package file for distribution in debs/.

Details Table

Order	Function Name	Overridable	Description
0.1	error_exit	no	Stop script and output error.
0.2	download	no	Utility function to download any file.
0.3	setup_golang	no	Setup Go Build environment.
0.4	setup_rust	no	Setup Cargo Build.
0.5	setup_ninja	no	Setup Ninja make system.
0.6	setup_meson	no	Setup Meson configure system.
0.7	setup_cmake	no	Setup CMake configure system.
1	handle_arguments	no	Handle command line arguments.
2	setup_variables	no	Setup essential variables like directory locations and flags.
3	handle_buildarch	no	Determines architecture to build for.
4	get_repo_files	no	Install dependencies if -i option supplied.
4.1	download_deb	no	Download packages for installation
5	start_build	no	Setup directories and files required. Read build.sh for variables.
6	extract_package	yes	Download source package.
7	post_extract_package	yes	Hook to run commands before host builds.
8	handle_host_build	yes	Determine whether a host build is required.
8.1	host_build	yes	Conduct a host build.
9	setup_toolchain	no	Setup C Toolchain from Android NDK.
10	patch_package	no	Patch all *.patch files as specified in the package directory.
11	replace_guess_scripts	no	Replace config.sub and config.guess scripts.
12	pre_configure	yes	Hook to run commands before configures.
13	configure	yes	Determine the configure method.
13.1	configure_autotools	no	Run configure by GNU Autotools.
13.2	configure_cmake	no	Run cmake.
13.3	configure_meson	no	Run meson.
14	post_configure	yes	Hook to run commands before make.
15	make	yes	Make the package.
16	make_install	yes	Install the package.
17	post_make_install	yes	Hook before extraction.
18	extract_into_massagedir	No with make_install	Extracts installed files.
19	massage	no	Remove unusable files and creates subpackages.
20	post_massage	yes	Final hook before packaging.
21	create_datatar	no	Archive package files.
22	create_debfile	no	Create package.
22.1	create_debscripts	yes	Create additional Debian package files.
23	compare_debfiles	no	Compare packages if -i option is specified.
24	finish_build	no	Notification of finish.

Order specifies function sequence. 0 order specifies utility functions.

Suborder specifies a function triggered by the main function. Functions with different suborders are not executed simultaneously.

For more detailed descriptiom on each step, you can read build-package.sh

Normal Build Process

Remarks: Software Developers should provide build instructions. Otherwise good luck trying how to build 😂.

Follow the instructions until you get a working build. If a build succeeds after any step, skip the remaining steps.

1. Create a build.sh file using the sample package template.

2. Create a subpackage.sh for each subpackage using the sample package template.

3. Run ./build-package.sh $PKG to see what errors are found.

4. If any steps complain about an error line, first copy the file to another directory.

5. Edit the original file.

6. When tests succeed for the file, create a patch by diff -u <original> <new> > packages/<pkg>/<filename>.patch

7. Repeat steps 2-4 for each error file.

8. If extra configuration or make arguments are needed, specify in build.sh as shown in sample package.

9. If there are subpackages, include them in subpackage.sh.

10. (optional but appreciated) Test the package by yourself.

Common Porting Problems

• The Android bionic libc does not have iconv and gettext/libintl functionality built in. A libandroid-support package contains these and may be used by all packages.

• "error: z: no archive symbol table (run ranlib)" usually means that the build machines libz is used instead of the one for cross compilation, due to the builder library -L path being setup incorrectly.

• rindex(3) does not exist, but strrchr(3) is preferred anyway.

• <sys/termios.h> does not exist, but <termios.h> is the standard location.

• <sys/fcntl.h> does not exist, but <fcntl.h> is the standard location.

• <sys/timeb.h> does not exist (removed in POSIX 2008), but ftime(3) can be replaced with gettimeofday(2).

• <glob.h> does not exist, but is available through the libandroid-glob package.

• SYSV shared memory is not supported by the kernel. A libandroid-shmem package, which emulates SYSV shared memory on top of the ashmem shared memory system, is available. Use it with LDFLAGS+=" -landroid-shmem.

• SYSV semaphores is not supported by the kernel. Use unnamed POSIX semaphores instead (named semaphores are unimplemented).

dlopen() and RTLD_* flags

<dlfcn.h> declares

	RTLD_NOW=0; RTLD_LAZY=1; RTLD_LOCAL=0; RTLD_GLOBAL=2;       RTLD_NOLOAD=4; // 32-bit
	RTLD_NOW=2; RTLD_LAZY=1; RTLD_LOCAL=0; RTLD_GLOBAL=0x00100; RTLD_NOLOAD=4; // 64-bit

These differs from glibc ones in that

1. They differ in value from glibc ones, so cannot be hardcoded in files (DLFCN.py in python does this)

2. They are missing some values (RTLD_BINDING_MASK, ...)

Android Dynamic Linker

The Android dynamic linker is located at /system/bin/linker (32-bit) or /system/bin/linker64 (64-bit). Here are source links to different versions of the linker:

• Android 5.0 linker

• Android 6.0 linker

• Android 7.0 linker

Some notes about the linker:

• The linker warns about unused dynamic section entries with a WARNING: linker: $BINARY: unused DT entry: type ${VALUE_OF_d_tag} message.

• The supported types of dynamic section entries has increased over time.

• The Termux build system uses termux-elf-cleaner to strip away unused ELF entries causing the above mentioned linker warnings.

• Symbol versioning is supported only as of Android 6.0, so is stripped away.

• DT_RPATH, the list of directories where the linker should look for shared libraries, is not supported, so is stripped away.

• DT_RUNPATH, the same as above but looked at after LD_LIBRARY_PATH, is supported only from Android 7.0, so is stripped away.

• Symbol visibility when opening shared libraries using dlopen() works differently. On a normal linker, when an executable linking against a shared library libA dlopen():s another shared library libB, the symbols of libA are exposed to libB without libB needing to link against libA explicitly. This does not work with the Android linker, which can break plug-in systems where the main executable dlopen():s a plug-in which doesn't explicitly link against some shared libraries already linked to by the executable. See the relevant NDK issue for more information.