Android: what changed

Revision 2 to 3. Removed lines have a minus sign; added lines have a plus sign.

Old	New		Line
1	1		All Articles about Android are listed in [[Portal:Android]].
2	2
3	3		(Android only)
4	4
5	5		## Android target
6	6
7	7		Support for the Android target is present starting from FPC 3.0.
8	8
9	9		Supported CPUs:
10	10
11	11		- ARM (`CPU_TARGET=arm`)
12	12		- x86 (`CPU_TARGET=i386`)
13	13		- MIPS (`CPU_TARGET=mipsel`)
14	14		- ARM64 (`CPU_TARGET=aaarch64`) - in FPC 3.2+
15	15		- x86-64 (`CPU_TARGET=x86_64`) - in FPC 3.2+
16	16		- [[FPC JVM\|JVM]] (not discussed on this page)
17	17
18	18		## Android NDK
19	19
20	20		You need to download and install Android NDK in order to get the cross binutils that compile programs for the android target on your current machine.
21	21
22	22		Download Android NDK using this link: <https://developer.android.com/ndk/downloads/index.html>
23	23
24	24		Extract it to some folder.
25	25
26	26		## Download FPC for Android
27	27
28	28		### Release version
29	29
30	30		If you develop for Android using a Windows machine you can download a setup package which contains cross-compilers for Android (ARM, i386, MIPS). After installation of the cross-compilers you can build binaries for Android without any additional steps.
31	31
32	32		For other host platforms you need to download the FPC sources archive and build a cross-compiler as described below.
33	33
34	34		Download the latest release cross-compilers and FPC sources here: <http://freepascal.org/download.html>
35	35
36	36		### Development version
37	37
38	38		The development (trunk) version of FPC may contain new features or bug fixes compared to the latest release version.
39	39
40	40		Check out the latest trunk sources of FPC using the following command:
41	41
42		-	~~`git clone https://gitlab.com/freepascal.org/fpc/source.git fpcsrc`~~
	42	+	```
	43	+	git clone https://gitlab.com/freepascal.org/fpc/source.git fpcsrc
	44	+	```
43	45
44	46		Now you have the latest compiler sources in the `fpcsrc` sub-folder.
45	47
46	48		## Building cross compiler
47	49
48	50		You need to have a working installation of the latest version of FPC for your host platform in order to create the cross-compiler.
49	51
50	52		This tutorial describes how to build a cross-compiler for the `arm-android` target on Windows. But the tutorial can be applied to any system with small obvious modifications.
51	53
52	54		Use the similar approach to build a `aarch64-android` or `i386-android` or `x86_64-android` or `mipsel-android` cross-compiler.
53	55
54	56		Let's assume the following paths:
55	57
56	58		- Android NDK path: `C:\Program Files\Android SDK\android-ndk-r12b`
57	59		- FPC svn sources path: `C:\Develop\FPC\fpcsrc`
58	60		- The cross-compiler installation path: `C:\Develop\FPC\pp`
59	61
60	62		Add the path to Android binutils to the PATH environment variable. In this tutorial the path is: `C:\Program Files\Android SDK\android-ndk-r12b\toolchains\arm-linux-androideabi-4.9\prebuilt\windows\bin`
61	63
62	64		Open the Command line prompt and `cd` to the root of FPC sources folder: `C:\Develop\FPC\fpcsrc`
63	65
64	66		Execute the following command:
65	67
66		-	~~`make clean crossall crossinstall OS_TARGET=android CPU_TARGET=arm INSTALL_PREFIX=C:\Develop\FPC\pp`~~
	68	+	```
	69	+	make clean crossall crossinstall OS_TARGET=android CPU_TARGET=arm INSTALL_PREFIX=C:\Develop\FPC\pp
	70	+	```
67	71
68	72		After that you should have the cross-compiler and units installed in folder `C:\Develop\FPC\pp` By default all units are built with -O2 optimization switch. Also software FPU emulation is used for ARM CPU by default. If you need to specify different compiler options for building, use the `CROSSOPT` parameter. For example if you wish to build units with hardware FPU support and ARMv7a CPU use the following command:
69	73
70		-	~~`make clean crossall crossinstall OS_TARGET=android CPU_TARGET=arm CROSSOPT="-Cparmv7a -Cfvfpv3" INSTALL_PREFIX=C:\Develop\FPC\pp`~~
	74	+	```
	75	+	make clean crossall crossinstall OS_TARGET=android CPU_TARGET=arm CROSSOPT="-Cparmv7a -Cfvfpv3" INSTALL_PREFIX=C:\Develop\FPC\pp
	76	+	```
71	77
72	78		Now create a new `fpc.cfg` file in folder `C:\Develop\FPC\pp\bin\i386-win32` and paste into it the following text:
73	79
74	80		-FuC:\Develop\FPC\pp\units\$FPCTARGET*
75	81
76	82		#ifdef android
77	83		#ifdef cpuarm
78	84		-FlC:\Program Files\Android SDK\android-ndk-r12b\platforms\android-21\arch-arm\usr\lib
79	85		#endif
80	86		#ifdef cpuaarch64
81	87		-FlC:\Program Files\Android SDK\android-ndk-r12b\platforms\android-21\arch-arm64\usr\lib
82	88		#endif
83	89		#ifdef cpui386
84	90		-FlC:\Program Files\Android SDK\android-ndk-r12b\platforms\android-21\arch-x86\usr\lib
85	91		#endif
86	92		#ifdef cpux86_64
87	93		-FlC:\Program Files\Android SDK\android-ndk-r12b\platforms\android-21\arch-x86_64\usr\lib
88	94		#endif
89	95		#ifdef cpumips32
90	96		-FlC:\Program Files\Android SDK\android-ndk-r12b\platforms\android-21\arch-mips\usr\lib
91	97		#endif
92	98		#endif
93	99
94	100		## Compiling programs
95	101
96	102		Now, when the cross-compiler is ready, you can compile programs for the Android target:
97	103
98		-	~~`C:\Develop\FPC\pp\bin\i386-win32\ppcrossarm -Tandroid testprog.pas`~~
	104	+	```
	105	+	C:\Develop\FPC\pp\bin\i386-win32\ppcrossarm -Tandroid testprog.pas
	106	+	```
99	107
100	108		## Notes
101	109
102	110		- The compiler does NOT define `LINUX` during compilation! It defines `UNIX` and `ANDROID` though.\
103	111		(Background: Android is not completely Linux compatible, e.g. a few syscalls and default library functions e.g. in pthreads, ... are missing, and it generally behaves different in a few ways. This makes the amount of defines manageable by avoiding `if defined(linux) and not defined(android)`. Actually, the list of things that are different is only growing).
104	112
105	113		- Shared libraries do not have `argc/argv` available (i.e. set to 0 or nil) because of Android.
106	114
107	115		- The System unit contains some useful [Android-specific functions](https://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/rtl/android/sysandroidh.inc?view=markup).
108	116
109	117		- The compiler and RTL do special processing for JNI shared libraries. The compiler treats a library as a JNI library only if the library exports the `JNI_OnLoad` function. Therefore, if you are creating a JNI shared library, always export `JNI_OnLoad`, even if it is empty.
110	118
111	119		- For JNI shared libraries standard output and error output are redirected to the Android system log. Therefore you can use `writeln()` to write to the system log.
112	120
113	121		- By default FPC builds PIC enabled shared libraries and executables for the Android target. PIC shared libraries work on any Android version (tested even on Android 1.5). But PIC executables can run only on Android 4.1+. To run executables on older versions of Android you need to disable PIC by passing the `-Cg-` switch to the compiler.
114	122
115	123		## Known issues
116	124
117	125		- Shared libraries compiled with FPC 3.0 does not work on Android 6.0+ and executables does not run on Android 5.0+. Starting from Android 6.0 (Marshmallow), it is required to build PIC compatible shared libraries. Starting from Android 5.0 (Lollipop), it is required to build PIC compatible executables (PIE).**\
118	126		PIC support for the Android target is present starting from FPC 3.0.2.**\
119	127		NOTE: By default FPC 3.0.2+ builds PIC enabled shared libraries and executables for the Android target. PIC shared libraries work on any Android version (tested even on Android 1.5). But PIC executables can run only on Android 4.1+. To run executables on older versions of Android you need to disable PIC by passing the `-Cg-` switch to the compiler.
120	128		- Shared libraries compiled with FPC 3.0.x does not work on Android 8.0+ when an application targets API 26+. This is caused by usage of syscalls which are blocked by SECCOMP starting from Android 8.\
121	129		This issue is fixed in FPC 3.2.
122	130		- If you use the cwstring unit in a JNI shared library, your Java application will hang when loading the library on Android 4.0 or earlier. This also applies to any unit which dynamically loads shared libraries during initialization. See more information below.\
123	131		This issue is fixed in FPC 3.2.
124	132		- The clocale unit is not implemented in FPC 3.0.\
125	133		It is implemented in FPC 3.2.
126	134		- The netdb unit is unusable in FPC 3.0 due to missing configuration of DNS servers.\
127	135		This issue is fixed in FPC 3.2.
128	136		- The `Now` function always returns a GMT time in FPC 3.0.\
129	137		This issue is fixed in FPC 3.2.
130	138		- The following functions return unusable paths in FPC 3.0: `GetTempDir, GetAppConfigDir, GetAppConfigFile, GetUserDir`.\
131	139		This issue is fixed in FPC 3.2.
132	140
133	141		## Freeze during shared library initialization on Android prior 4.1
134	142
135	143		If your shared library contains a unit which performs dynamic loading of other shared libraries using `LoadLibaray()` or `dlopen()`, your library may fail to load on Android 4.0 or earlier. The library loading will freeze in such case. One of the units, which can trigger the issue is cwstring.
136	144
137	145		Due to a bug in Android versions prior to 4.1, the `dlopen()` API function does not support recursive calls. When a shared library is being loaded by JVM, using `dlopen()`, the library initialization is executed, including initialization code of all units in the library. If a unit initialization code calls `dlopen()` - it simply hangs, since the initial `dlopen()` is not finished yet and recursion is not allowed.
138	146
139	147		This issue is fixed in FPC 3.2.0: To workaround this issue the compiler uses the following trick: If a library exports `JNI_OnLoad()`, then no unit initialization is performed during library load. The initialization is called when JVM has loaded the library and then calls `JNI_OnLoad()`.
140	148
141	149		Therefore, if you are creating a JNI shared library, always export `JNI_OnLoad`, even if it is empty.
142	150
143	151		Also you can trigger this bug if you have a JNI shared library, which use other shared library, created using FPC. The loading of this second library may hang. To workaround this, you need to export an empty `JNI_OnLoad()` function in the second library. Then you need to call `JNI_OnLoad()` from the initialization of the first library.
144	152
145	153		## See also
146	154
147	155		- [[Android tutorial]]
148	156		- You can use the [[pas2jni]] utility to easily create JNI shared libraries from your existing code and use it in Android native Java applications.
149	157		- [[Cross compiling]] for cross compiling from Linux, macOS and Windows along with other useful cross-compilation information.
150	158
151	159		## External links
152	160
153	161		- [Tutorial "Lazarus and Android"](http://sourceforge.net/projects/laztoapk/files/Lazarus%20and%20Android.pdf/download) (PDF file)
154	162		- [How to create Android apps with Lazarus](https://pascaldelphilazarus.wordpress.com/2014/06/02/how-to-create-android-apps-with-lazarus/)
155	163		- [How to setup cross-compilation to Android](https://forum.lazarus.freepascal.org/index.php/topic,32553.0.html) (Lazarus Forum)
156	164
157	165		---
158	166		From the Free Pascal wiki, page "Android", as it stood on 2021-11-22 after a change by BeniBela, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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