Mailman 3 Undefined dlopen When Building Module On Android - Python-Dev

Undefined dlopen When Building Module On Android

Cyd Haselton

19 Jan 2015 19 Jan '15

8:21 p.m.

Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know. I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc) I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error. If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again. If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors. Let me know if you need me to provide additional information. Any help would be greatly appreciated. Cyd

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Cyd Haselton

20 Jan 20 Jan

4:53 a.m.

On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...

Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors.

Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is) 16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.pyc", O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0 *snip call to libc intercepted by libfakechroot* 16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied) See attached for remainder

Cyd Haselton

22 Jan 22 Jan

4:13 a.m.

On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...

On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...
Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors.

Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.pyc", O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed?

Guido van Rossum

4:23 a.m.

Maybe try a list focused on Android development? Few people in the Python core development community have any Android experience. But the issues and context you offer seem to be related to the Android world, not to Python. (dlopen is used by a lot of systems, not just Python.) On Wed, Jan 21, 2015 at 2:43 PM, Cyd Haselton wrote:

...

On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...
Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors.

Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513

open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.pyc",

...
O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed? _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido%40python.org

-- --Guido van Rossum (python.org/~guido)

Brett Cannon

8:03 p.m.

A mobile SIG is being formed, but it doesn't have a mailing list yet, else that would be a good place to ask this question. On Wed Jan 21 2015 at 5:54:39 PM Guido van Rossum wrote:

...

Maybe try a list focused on Android development? Few people in the Python core development community have any Android experience. But the issues and context you offer seem to be related to the Android world, not to Python. (dlopen is used by a lot of systems, not just Python.)

On Wed, Jan 21, 2015 at 2:43 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...
Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors.

Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513

open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.pyc",

...
O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed?

_______________________________________________

...
Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev

Unsubscribe:

...
https://mail.python.org/mailman/options/python-dev/guido%40python.org

-- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/ brett%40python.org

Cyd Haselton

23 Jan 23 Jan

10:20 p.m.

I guess I'll keep waiting...given the zero responses I've gotten from the android side. :-(. In the meantime...in case anyone is interested... since I have the working binary, I executed it and went through each command in setup.py to see what throws the 'undefined reference to dlopen' error. Turns out that the distutils module is the culprit...specifically distutils.core. On Thu, Jan 22, 2015 at 8:33 AM, Brett Cannon wrote:

...

A mobile SIG is being formed, but it doesn't have a mailing list yet, else that would be a good place to ask this question.

On Wed Jan 21 2015 at 5:54:39 PM Guido van Rossum wrote:

...
Maybe try a list focused on Android development? Few people in the Python core development community have any Android experience. But the issues and context you offer seem to be related to the Android world, not to Python. (dlopen is used by a lot of systems, not just Python.)

On Wed, Jan 21, 2015 at 2:43 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...
Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other errors.

Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513

open("/data/data/jackpal.androidterm/kbox2/bld/python/Python-2.7.8/Lib/distutils/unixccompiler.pyc", O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed?

_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev

Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido%40python.org

-- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/brett%40python.org

Frank, Matthew I

25 Jan 25 Jan

4:38 a.m.

Android's dlopen() works slightly differently than the normal Unix dlopen() in at least two different ways. I haven't seen your particular problem, but that's probably because I'm cross-building CPython (building everything I need on a Linux machine, and then copying the install directory to the Android machine.) (1) When building for Android you need to explicitly include the "-ldl" flag on the command line for the link step. (In Linux the dlopen() routine is included in libc, so "-ldl" is not necessary). I suspect that some part of your distutils was not linked correctly. (Since I'm cross-building I've never run distutils on the Android side, which is probably why I've not seen this.) Your best bet would be to run under a debugger and figure out which line of C code in which .so file is throwing the error. Then going back to the build scripts and looking at how that .so file is getting linked. (For an example of someone else having a similar problem see for example, http://stackoverflow.com/questions/25846927/git-built-on-android-throws-unde...). (2) The other possibility has to do with a quirk in Android's dlopen() implementation. On most legacy Unix systems (including Linux) when you dlopen() a library Z then all the already loaded libraries A, B, C, ... are searched for any dependences of Z (even if Z was not explicitly linked against any of A, B, C,...). On Android (perhaps for security reasons) that's not true, if Z depends on A, then you need to have "-lA" when you link Z. An example (and patch) for this problem is http://bugs.python.org/issue21668. -Matt

...

-----Original Message----- From: Cyd Haselton [mailto:chaselton@gmail.com] Sent: Friday, January 23, 2015 10:50 AM To: Brett Cannon Cc: Guido van Rossum; Python-Dev Subject: Re: [Python-Dev] Undefined dlopen When Building Module On Android

I guess I'll keep waiting...given the zero responses I've gotten from the android side. :-(.

In the meantime...in case anyone is interested... since I have the working binary, I executed it and went through each command in setup.py to see what throws the 'undefined reference to dlopen' error. Turns out that the distutils module is the culprit...specifically distutils.core.

On Thu, Jan 22, 2015 at 8:33 AM, Brett Cannon wrote:

...
A mobile SIG is being formed, but it doesn't have a mailing list yet, else that would be a good place to ask this question.

On Wed Jan 21 2015 at 5:54:39 PM Guido van Rossum wrote:

...
Maybe try a list focused on Android development? Few people in the Python core development community have any Android experience. But the issues and context you offer seem to be related to the Android world, not to

Python.

...
(dlopen is used by a lot of systems, not just Python.)

On Wed, Jan 21, 2015 at 2:43 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote:

...
Hello, I'm struggling with a build issue on Android; I've posted to the general python list with no result, so I'm re-posting here in hopes that someone can help. If this is the wrong place feel free to let me know.

I'm attempting to build Python 2.7.8 on my Android device; I'm using an environment that simulates a Linux filesystem within the Android terminal using a port of fakechroot. Within that environment I've ported and/or bootstrapped a number of Linux utilities (curl, git, openssl, gcc)

I run ./configure, then make, and the executable and library are built. The problem occurs when build_ext is run; the newly built python executable builds, then links _struct, and immediately afterwards I get an 'undefined reference to dlopen' error.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='c dl m' -f, the 'undefined reference to dlopen' error is thrown again.

If I run ./python setup.py --verbose -library-dirs /path/to/lib --libraries='-lc -ldl -lm' -f the build continues past _struct...even though ld throws the expected 'unable to find -l-lc' and other

errors.

...
...
...
Let me know if you need me to provide additional information. Any help would be greatly appreciated.

Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python- 2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513

open("/data/data/jackpal.androidterm/kbox2/bld/python/Python- 2.7.8/Lib/distutils/unixccompiler.pyc", O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed?

_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev

Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido%40python.or g

-- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/brett%40python.org

Cyd Haselton

5:07 a.m.

Replies in body of message for clarity: On Sat, Jan 24, 2015 at 5:08 PM, Frank, Matthew I wrote:

...

Android's dlopen() works slightly differently than the normal Unix dlopen() in at least two different ways. I haven't seen your particular problem, but that's probably because I'm cross-building CPython (building everything I need on a Linux machine, and then copying the install directory to the Android machine.)

Yeah...I have a Linux machine but it currently resides as a gunzipped tarball on an external drive...I lack the space to decompress and use it for building purposes.

...

(1) When building for Android you need to explicitly include the "-ldl" flag on the command line for the link step. (In Linux the dlopen() routine is included in libc, so "-ldl" is not necessary). I suspect that some part of your distutils was not linked correctly. (Since I'm cross-building I've never run distutils on the Android side, which is probably why I've not seen this.) Your best bet would be to run under a debugger and figure out which line of C code in which .so file is throwing the error. Then going back to the build scripts and looking at how that .so file is getting linked. (For an example of someone else having a similar problem see for example, http://stackoverflow.com/questions/25846927/git-built-on-android-throws-unde...).

Funny you should reference that post as I'm the one who started it; I ported git, which required curl and openssl ports, a while ago and...as I think I mentioned in that post...I had to go back and re-port openssl, making sure to throw in -ldl wherever possible. Python (which I'm building in the same environment in which I built openssl, git and curl) is a different beast altogether. Environment variables that make it to the Makefile don't make it into the modules built by setup.py, which is run by distutils, which I wasn't aware was built alongside Python until you mentioned it just now. Then there are the modules in Setup...which are built or not...seemingly independently of whether or not the line specifying the module is commented out or not; the hack workaround is to put every module that should be excluded in setup.py...even if it is commented out in Setup. Obviously I'm still trying to get a handle on the Python build process.

...

(2) The other possibility has to do with a quirk in Android's dlopen() implementation. On most legacy Unix systems (including Linux) when you dlopen() a library Z then all the already loaded libraries A, B, C, ... are searched for any dependences of Z (even if Z was not explicitly linked against any of A, B, C,...). On Android (perhaps for security reasons) that's not true, if Z depends on A, then you need to have "-lA" when you link Z. An example (and patch) for this problem is http://bugs.python.org/issue21668.

Thanks for the bit of info above...very useful. I've included -lc -ldl in the requisite places in Setup, and setup.py...although it's entirely possible I've not added it to places that need it given that I'm still struggling to understand the build process. Right now I'm at the point where running configure && make finishes successfully but throws warnings during the module build and import process. Running make install fails completely with the same 'undefined reference to dlopen' because, for some reason, make install requires the sharedmods target to be rebuilt again, which fails because setup.py fails when importing distutils.core. Why it doesn't do the same when running make is beyond me. Cyd

Cyd Haselton

8:24 a.m.

Closer. make && make install ran successfully; however running the newly installed binary results in the same error. On Sat, Jan 24, 2015 at 5:08 PM, Frank, Matthew I wrote:

...

Android's dlopen() works slightly differently than the normal Unix dlopen() in at least two different ways. I haven't seen your particular problem, but that's probably because I'm cross-building CPython (building everything I need on a Linux machine, and then copying the install directory to the Android machine.)

(1) When building for Android you need to explicitly include the "-ldl" flag on the command line for the link step. (In Linux the dlopen() routine is included in libc, so "-ldl" is not necessary). I suspect that some part of your distutils was not linked correctly. (Since I'm cross-building I've never run distutils on the Android side, which is probably why I've not seen this.) Your best bet would be to run under a debugger and figure out which line of C code in which .so file is throwing the error. Then going back to the build scripts and looking at how that .so file is getting linked. (For an example of someone else having a similar problem see for example, http://stackoverflow.com/questions/25846927/git-built-on-android-throws-unde...).

(2) The other possibility has to do with a quirk in Android's dlopen() implementation. On most legacy Unix systems (including Linux) when you dlopen() a library Z then all the already loaded libraries A, B, C, ... are searched for any dependences of Z (even if Z was not explicitly linked against any of A, B, C,...). On Android (perhaps for security reasons) that's not true, if Z depends on A, then you need to have "-lA" when you link Z. An example (and patch) for this problem is http://bugs.python.org/issue21668.

-Matt

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-----Original Message----- From: Cyd Haselton [mailto:chaselton@gmail.com] Sent: Friday, January 23, 2015 10:50 AM To: Brett Cannon Cc: Guido van Rossum; Python-Dev Subject: Re: [Python-Dev] Undefined dlopen When Building Module On Android

I guess I'll keep waiting...given the zero responses I've gotten from the android side. :-(.

In the meantime...in case anyone is interested... since I have the working binary, I executed it and went through each command in setup.py to see what throws the 'undefined reference to dlopen' error. Turns out that the distutils module is the culprit...specifically distutils.core.

On Thu, Jan 22, 2015 at 8:33 AM, Brett Cannon wrote:

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A mobile SIG is being formed, but it doesn't have a mailing list yet, else that would be a good place to ask this question.

On Wed Jan 21 2015 at 5:54:39 PM Guido van Rossum wrote:

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Maybe try a list focused on Android development? Few people in the Python core development community have any Android experience. But the issues and context you offer seem to be related to the Android world, not to

Python.

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(dlopen is used by a lot of systems, not just Python.)

On Wed, Jan 21, 2015 at 2:43 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 5:23 PM, Cyd Haselton wrote:

...
On Mon, Jan 19, 2015 at 8:51 AM, Cyd Haselton wrote: > Hello, > I'm struggling with a build issue on Android; I've posted to the > general python list with no result, so I'm re-posting here in > hopes that someone can help. If this is the wrong place feel > free to let me know. > > I'm attempting to build Python 2.7.8 on my Android device; I'm > using an environment that simulates a Linux filesystem within the > Android terminal using a port of fakechroot. Within that > environment I've ported and/or bootstrapped a number of Linux > utilities (curl, git, openssl, gcc) > > I run ./configure, then make, and the executable and library are > built. The problem occurs when build_ext is run; the newly built > python executable builds, then links _struct, and immediately > afterwards I get an 'undefined reference to dlopen' error. > > If I run ./python setup.py --verbose -library-dirs /path/to/lib > --libraries='c dl m' -f, the 'undefined reference to dlopen' > error is thrown again. > > If I run ./python setup.py --verbose -library-dirs /path/to/lib > --libraries='-lc -ldl -lm' -f the build continues past > _struct...even though ld throws the expected 'unable to find -l-lc' and other

errors.

...
...
> > Let me know if you need me to provide additional information. > Any help would be greatly appreciated. > > Cyd

Additionally I took a strace of the error producing command. The following is (hopefully) a relevant portion minus the various 'no such file' lines before the correct lib is found (which it always is)

16513 open("/data/data/jackpal.androidterm/kbox2/bld/python/Python- 2.7.8/Lib/distutils/unixccompiler.py", O_RDONLY|O_LARGEFILE) = 3 16513

open("/data/data/jackpal.androidterm/kbox2/bld/python/Python- 2.7.8/Lib/distutils/unixccompiler.pyc", O_RDONLY|O_LARGEFILE) = 4 16513 vfork() = 16525 16513 wait4(16525, 16525 open("/data/data/jackpal.androidterm/kbox2/bin/sh", O_RDONLY|O_LARGEFILE) = 3 16525 execve("/data/data/jackpal.androidterm/kbox2/bin/sh", ["sh", "-c", "gcc --sysroot=/usr/gcc-4.9.2/sysroot -print-multiarch > build/temp.linux-armv7l-2.7/multiarch 2> /dev/null"], [/* 58 vars */]) = 0

*snip call to libc intercepted by libfakechroot*

16525 open("/system/lib/libc.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/system/lib/libm.so", O_RDONLY|O_LARGEFILE|0x80000) = 3 16525 open("/dev/__properties__", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|0x80000) = 3 16525 open("build/temp.linux-armv7l-2.7/multiarch", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 open("/data/data/jackpal.androidterm/kbox2/dev/null", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3 16525 fork() = 16526 16525 wait4(-1, 16526 open("/acct/uid/10186/tasks", O_RDWR|O_CREAT|O_LARGEFILE, 0666) = -1 EACCES (Permission denied)

See attached for remainder

Should I be posting this issue elsewhere? Is more information needed?

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Undefined dlopen When Building Module On Android

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