termux-packages/docs/BUILD.md

Build Documentation

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

Flow of a Build

Basics

Package build flow is controlled by script build-package.sh and is split into the following stages:

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	termux_error_exit	no	Stop script and output error.
0.2	termux_download	no	Utility function to download any file.
0.3	termux_setup_golang	no	Setup Go Build environment.
0.4	termux_setup_rust	no	Setup Cargo Build.
0.5	termux_setup_ninja	no	Setup Ninja make system.
0.6	termux_setup_meson	no	Setup Meson configure system.
0.7	termux_setup_cmake	no	Setup CMake configure system.
1	termux_step_handle_arguments	no	Handle command line arguments.
2	termux_step_setup_variables	no	Setup essential variables like directory locations and flags.
3	termux_step_handle_buildarch	no	Determines architecture to build for.
4	termux_step_get_repo_files	no	Install dependencies if -i option supplied.
4.1	termux_download_deb	no	Download packages for installation
5	termux_step_start_build	no	Setup directories and files required. Read build.sh for variables.
6	termux_step_extract_package	yes	Download source package.
7	termux_step_post_extract_package	yes	Hook to run commands before host builds.
8	termux_step_handle_host_build	yes	Determine whether a host build is required.
8.1	termux_step_host_build	yes	Conduct a host build.
9	termux_step_setup_toolchain	no	Setup C Toolchain from Android NDK.
10	termux_step_patch_package	no	Patch all *.patch files as specified in the package directory.
11	termux_step_replace_guess_scripts	no	Replace config.sub and config.guess scripts.
12	termux_step_pre_configure	yes	Hook to run commands before configures.
13	termux_step_configure	yes	Determine the configure method.
13.1	termux_step_configure_autotools	no	Run configure by GNU Autotools.
13.2	termux_step_configure_cmake	no	Run cmake.
13.3	termux_step_configure_meson	no	Run meson.
14	termux_step_post_configure	yes	Hook to run commands before make.
15	termux_step_make	yes	Make the package.
16	termux_step_make_install	yes	Install the package.
17	termux_step_post_make_install	yes	Hook before extraction.
18	termux_step_extract_into_massagedir	no with make_install	Extracts installed files.
19	termux_step_massage	no	Remove unusable files and creates subpackages.
20	termux_step_post_massage	yes	Final hook before packaging.
21	termux_step_create_datatar	no	Archive package files.
22	termux_step_create_debfile	no	Create package.
22.1	termux_step_create_debscripts	yes	Create additional Debian package files.
23	termux_step_compare_debfiles	no	Compare packages if -i option is specified.
24	termux_step_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 either in README or INSTALL files. 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 4-6 for each error file.

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

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

Common Porting Problems

• Most programs expect that target is FHS compliant. They have hardcoded paths like /etc, /bin, /usr/share, /tmp which are not available in Termux at standard locations but only in $TERMUX_PREFIX.

• 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 machine's 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).

• Starting from Android 8, a Seccomp was enabled for applications. Seccomp forbids usage of some system calls which results in crash with Bad system call errors.

• Starting from Android 8, programs cannot use tcsetattr() with TCSAFLUSH parameter due to SELinux. Use TCSANOW instead.

• Starting from Android 9, Seccomp began to block setuid()-related system calls. Since Termux is primarily for single-user non-root usage, setuid/setgid functionality is discouraged anyway.

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 have 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.