docs: update BUILD.md
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Leonid Pliushch
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docs/BUILD.md
114
docs/BUILD.md
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@ -6,25 +6,34 @@ This document is intended to describe how to build a package.
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### Basics
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Package build flow is controlled by script [build-package.sh](../build-package.sh) and is split into the following stages:
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Package build flow is controlled by script [build-package.sh](../build-package.sh)
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and is split into the following stages:
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1. Read `packages/$PKG/build.sh` to obtain package metadata (e.g. version, description, dependencies), URLs for source code and steps to build package.
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1. Read `packages/$PKG/build.sh` to obtain package metadata (e.g. version,
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description, dependencies), URLs for source code and steps to build package.
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2. Extract the archives with source code into `$HOME/.termux-build/$PKG/src`. This step is not performed when `TERMUX_PKG_SKIP_SRC_EXTRACT` is set.
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2. Extract the archives with source code into `$HOME/.termux-build/$PKG/src`.
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This step is not performed when `TERMUX_PKG_SKIP_SRC_EXTRACT` is set.
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3. Build package for the host. This step is performed only when `TERMUX_PKG_HOSTBUILD` is set.
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3. Build package for the host. This step is performed only when
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`TERMUX_PKG_HOSTBUILD` is set.
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4. Set up a standalone Android NDK toolchain and patch NDK sysroot from patches located in [ndk-patches](../ndk-patches) directory. This step performed only one time per each architecture.
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4. Set up a standalone Android NDK toolchain and patch NDK sysroot from patches
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located in [ndk-patches](../ndk-patches) directory. This step performed only
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one time per each architecture.
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5. Search for patches in `packages/$TERMUX_PKG_NAME/*.patch` and apply them.
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6. Build the package under directory `$HOME/.termux-build/$PKG/build`. If `TERMUX_PKG_BUILD_IN_SRC` is set, then build will be done in directory `$HOME/.termux-build/$PKG/src`.
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6. Build the package under directory `$HOME/.termux-build/$PKG/build`. If
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`TERMUX_PKG_BUILD_IN_SRC` is set, then build will be done in directory `$HOME/.termux-build/$PKG/src`.
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7. Install built stuff into `$TERMUX_PREFIX`.
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8. Find modified files in `$TERMUX_PREFIX` and extract them into `$HOME/.termux-build/$PKG/massage`.
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8. Find modified files in `$TERMUX_PREFIX` and extract them into
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`$HOME/.termux-build/$PKG/massage`.
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9. Perform "massage" on files in `$HOME/.termux-build/$PKG/massage`. For example, split files between subpackages.
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9. Perform "massage" on files in `$HOME/.termux-build/$PKG/massage`. For example,
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split files between subpackages.
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10. Create a debian archive file that is ready for distribution.
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@ -74,15 +83,18 @@ Package build flow is controlled by script [build-package.sh](../build-package.s
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Order specifies function sequence. 0 order specifies utility functions.
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Suborder specifies a function triggered by the main function. Functions with different suborders are not executed simultaneously.
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Suborder specifies a function triggered by the main function. Functions with
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different suborders are not executed simultaneously.
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For more detailed descriptiom on each step, you can read [build-package.sh](../build-package.sh)
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## Normal Build Process
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Remarks: Software Developers should provide build instructions either in README or INSTALL files. Otherwise good luck trying how to build :joy:.
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Remarks: Software Developers should provide build instructions either in README
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or INSTALL files. Otherwise good luck trying how to build :joy:.
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Follow the instructions until you get a working build. If a build succeeds after any step, skip the remaining steps.
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Follow the instructions until you get a working build. If a build succeeds after
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any step, skip the remaining steps.
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1. Create a `build.sh` file using the [sample package template](sample/build.sh).
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@ -90,45 +102,66 @@ Follow the instructions until you get a working build. If a build succeeds after
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3. Run `./build-package.sh $PKG` to see what errors are found.
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4. If any steps complain about an error line, first copy the file to another directory.
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4. If any steps complain about an error line, first copy the file to another
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directory.
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5. Edit the original file.
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6. When tests succeed for the file, create a patch by `diff -u <original> <new> > packages/<pkg>/<filename>.patch`
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6. When tests succeed for the file, create a patch by
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`diff -u <original> <new> > packages/<pkg>/<filename>.patch`
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7. Repeat steps 4-6 for each error file.
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8. If extra configuration or make arguments are needed, specify in `build.sh` as shown in sample package.
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8. If extra configuration or make arguments are needed, specify in `build.sh`
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as shown in sample package.
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9. (optional but appreciated) Test the package by yourself.
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## Common Porting Problems
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- Most programs expect that target is [FHS](https://uk.wikipedia.org/wiki/Filesystem_Hierarchy_Standard) compliant. They have hardcoded paths like `/etc`, `/bin`, `/usr/share`, `/tmp` which are not available in Termux at standard locations but only in `$TERMUX_PREFIX`.
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- Most programs expect that target is [FHS](https://uk.wikipedia.org/wiki/Filesystem_Hierarchy_Standard)
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compliant. They have hardcoded paths like `/etc`, `/bin`, `/usr/share`, `/tmp`
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which are not available in Termux at standard locations but only in `$TERMUX_PREFIX`.
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- 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.
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- The Android bionic libc does not have iconv and gettext/libintl functionality
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built in. A `libandroid-support` package contains these and may be used by all
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packages.
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- "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.
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- "error: z: no archive symbol table (run ranlib)" usually means that the build
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machine's libz is used instead of the one for cross-compilation due to the
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builder library -L path being setup incorrectly.
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- rindex(3) does not exist, but strrchr(3) is preferred anyway.
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- <sys/termios.h> does not exist, but <termios.h> is the standard location.
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- <sys/termios.h> does not exist, but <termios.h> is the standard
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location.
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- <sys/fcntl.h> does not exist, but <fcntl.h> is the standard location.
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- <sys/fcntl.h> does not exist, but <fcntl.h> is the standard
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location.
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- <sys/timeb.h> does not exist (removed in POSIX 2008), but ftime(3) can be replaced with gettimeofday(2).
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- <sys/timeb.h> does not exist (removed in POSIX 2008), but ftime(3) can
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be replaced with gettimeofday(2).
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- <glob.h> does not exist, but is available through the `libandroid-glob` package.
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- <glob.h> does not exist, but is available through the `libandroid-glob`
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package.
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- SYSV shared memory is not supported by the kernel. A `libandroid-shmem` package, which emulates SYSV shared memory on top of the [ashmem](http://elinux.org/Android_Kernel_Features#ashmem) shared memory system, is available. Use it with `LDFLAGS+=" -landroid-shmem`.
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- SYSV shared memory is not supported by the kernel. A `libandroid-shmem`
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package, which emulates SYSV shared memory on top of the [ashmem](http://elinux.org/Android_Kernel_Features#ashmem)
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shared memory system, is available. Use it with `LDFLAGS+=" -landroid-shmem`.
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- SYSV semaphores is not supported by the kernel. Use unnamed POSIX semaphores instead (named semaphores are unimplemented).
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- SYSV semaphores are not supported by the kernel. Use unnamed POSIX semaphores
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instead (named semaphores are unimplemented).
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- Starting from Android 8, a [Seccomp](https://android-developers.googleblog.com/2017/07/seccomp-filter-in-android-o.html) was enabled for applications. Seccomp forbids usage of some system calls which results in crash with `Bad system call` errors.
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- Starting from Android 8, a [Seccomp](https://android-developers.googleblog.com/2017/07/seccomp-filter-in-android-o.html)
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was enabled for applications. Seccomp forbids usage of some system calls
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which results in crash with `Bad system call` errors.
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- Starting from Android 8, programs cannot use `tcsetattr()` with `TCSAFLUSH` parameter due to SELinux. Use `TCSANOW` instead.
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- Starting from Android 8, programs cannot use `tcsetattr()` with `TCSAFLUSH`
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parameter due to SELinux. Use `TCSANOW` instead.
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- Starting from Android 9, [Seccomp](https://android-developers.googleblog.com/2017/07/seccomp-filter-in-android-o.html) began to block `setuid()`-related system calls. Since Termux is primarily for single-user non-root usage, setuid/setgid functionality is discouraged anyway.
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- Starting from Android 9, [Seccomp](https://android-developers.googleblog.com/2017/07/seccomp-filter-in-android-o.html)
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began to block `setuid()`-related system calls. Since Termux is primarily for
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single-user non-root usage, setuid/setgid functionality is discouraged anyway.
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### dlopen() and RTLD_* flags
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@ -139,13 +172,15 @@ RTLD_NOW=2; RTLD_LAZY=1; RTLD_LOCAL=0; RTLD_GLOBAL=0x00100; RTLD_NOLOAD=4; // 64
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```
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These differs from glibc ones in that
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1. They differ in value from glibc ones, so cannot be hardcoded in files (DLFCN.py in python does this)
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1. They differ in value from glibc ones, so cannot be hardcoded in files
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(DLFCN.py in python does this)
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2. They are missing some values (`RTLD_BINDING_MASK`, ...)
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### Android Dynamic Linker
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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:
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The Android dynamic linker is located at `/system/bin/linker` (32-bit) or
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`/system/bin/linker64` (64-bit). Here are source links to different versions of the linker:
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- [Android 5.0 linker](https://android.googlesource.com/platform/bionic/+/lollipop-mr1-release/linker/linker.cpp)
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@ -155,16 +190,29 @@ The Android dynamic linker is located at `/system/bin/linker` (32-bit) or `/syst
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Some notes about the linker:
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- The linker warns about unused [dynamic section entries](https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-42444.html) with a `WARNING: linker: $BINARY: unused DT entry: type ${VALUE_OF_d_tag}` message.
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- The linker warns about unused [dynamic section entries](https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-42444.html)
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with a `WARNING: linker: $BINARY: unused DT entry: type ${VALUE_OF_d_tag}`
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message.
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- The supported types of dynamic section entries have increased over time.
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- The Termux build system uses [termux-elf-cleaner](https://github.com/termux/termux-elf-cleaner) to strip away unused ELF entries causing the above mentioned linker warnings.
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- The Termux build system uses [termux-elf-cleaner](https://github.com/termux/termux-elf-cleaner)
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to strip away unused ELF entries causing the above mentioned linker warnings.
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- Symbol versioning is supported only as of Android 6.0, so is stripped away.
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- `DT_RPATH`, the list of directories where the linker should look for shared libraries is not supported, so is stripped away.
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- `DT_RPATH`, the list of directories where the linker should look for shared
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libraries is not supported, so is stripped away.
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- `DT_RUNPATH`, the same as above but looked at after `LD_LIBRARY_PATH`, is supported only from Android 7.0, so is stripped away.
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- `DT_RUNPATH`, the same as above but looked at after `LD_LIBRARY_PATH`, is
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supported only from Android 7.0, so is stripped away.
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- 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](https://github.com/android-ndk/ndk/issues/201) for more information.
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- Symbol visibility when opening shared libraries using `dlopen()` works
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differently. On a normal linker, when an executable linking against a shared
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library libA dlopen():s another shared library libB, the symbols of libA are
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exposed to libB without libB needing to link against libA explicitly. This
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does not work with the Android linker, which can break plug-in systems where
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the main executable dlopen():s a plug-in which doesn't explicitly link against
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some shared libraries already linked to by the executable.
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See [the relevant NDK issue](https://github.com/android-ndk/ndk/issues/201)
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for more information.
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