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Cross-build _curses failed if host ncurses headers and target ncurses headers have different layouts #72377
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In changeset 919259054621 (from bpo-12567) and 707761d59a4a (from bpo-15268), /usr/include/ncursesw was added to include paths in setup.py and configure.ac. This is wrong and breaks cross-compiling. For example, if host has /usr/include/ncursesw/ncurses.h and target has $SYSROOT/include/ncurses.h, the build fails. An example can be found in [1]. My patch removes all references to /usr/include/ncursesw and uses a robust detection, which is suitable for both native builds and cross builds. Added the authors of aforementioned changesets. [1] https://s3.amazonaws.com/archive.travis-ci.org/jobs/159936249/log.txt |
Hmmm, I don't know why Rietveld failed to recognize changes in configure. Maybe it's because I've modified the patch file manually? |
looks good to me, thanks for working on this. |
Now, Cygwin platform is able to build core interpreter on default branch. But the curses module has been failed to build. Therefore I tried to build curses module on Cygwin (Vista x86) using this patch. And it has been succeeded. |
Hmm it's surprising for me that an irrelevant patch fixes issues on Cygwin. Does test_curses pass? |
test_curses has been skipped almost. the skip reason has been written "cygwin's curses mostly just hangs" in test case class. |
A clean patch without changes in ./configure. autoreconf necessary |
the upstream ncurses has the ncursesw subdirinclude name, so you apparently can assume that this directory name is fixed *iff* it exists, however the ncursesw installation can be found in <prefix>/include instead. Can your changes cope with that? second issue is that you apparently don't do the changes for term.h (and possibly for other headers in other places as well, I only looked at the diff), so you mix ncursesw and ncurses headers. So you have to make these changes in all other places as well. Third issue is that you can't make these changes for third party extensions, if there are any relying on the ncurses/ncursesw distinction. fyi, "all" ncursesw headers are: /usr/include/ncursesw/curses.h |
term.h is included only if ncurses is missing and the system (SysV) curses is used, so I didn't change it. See below: #ifdef __sgi
#include <term.h>
#endif
#ifdef HAVE_NCURSES_H
#include <ncurses.h>
#else
#include <curses.h>
#ifdef HAVE_TERM_H
/* for tigetstr, which is not declared in SysV curses */
#include <term.h>
#endif
#endif
Did you mean 3rd party extensions that include py_curses.h may get broken with this patch? IMO they shouldn't include this as it's CPython's implementation detail and shouldn't be used outside Modules/_cursesmodule.c and Modules/_curses_panel.c
This is what I want to solve at the first place - make _curses compatible with different configurations. In configure.ac, there's a line: AC_CHECK_HEADERS(curses.h ncurses.h ncursesw/ncurses.h ncurses/ncurses.h panel.h ncursesw/panel.h ncurses/panel.h)
Did you mean there's no need to check panel.h? I'll try to update the patch. There's something missing from this patch: if ncurses is built with --enable-reentrant, the library and include paths get an additional 't'. For example, the library name becomes libncursestw.so and includedir becomes $prefix/include/ncursestw. Note that 't' comes before 'w' as ncurses's configure.in handles --enable-widec before --enable-reentrant. I skip such cases as --enable-reentrant is not compatible with Modules/_cursesmodule.c yet (bpo-25720). I'd like to postpone it until bpo-25720 is resolved as it does not make sense to detect incompatible header paths. |
The only change that is needed here is to not include /usr/include/ncursesw in setup.py when cross compiling to ensure that the headers of the build platform are not included. When cross compiling Python, it is the responsability of the packager to set the appropriate CPPFLAGS and LDFLAGS upon invoking configure, so that the curses headers are included and the curses libraries are linked at build time. |
No. Lots of codes in _cursesmodule.c need to know whether it's ncursesw, ncurses, or SysV's curses. For example: (segments below are from unpatched codebase) #if !defined(__hpux) || defined(HAVE_NCURSES_H)
/* On HP/UX 11, these are of type cchar_t, which is not an
integral type. If this is a problem on more platforms, a
configure test should be added to determine whether ACS_S1
is of integral type. */
SetDictInt("ACS_S1", (ACS_S1));
SetDictInt("ACS_S9", (ACS_S9));
SetDictInt("ACS_DIAMOND", (ACS_DIAMOND));
SetDictInt("ACS_CKBOARD", (ACS_CKBOARD));
SetDictInt("ACS_DEGREE", (ACS_DEGREE));
SetDictInt("ACS_PLMINUS", (ACS_PLMINUS));
SetDictInt("ACS_BULLET", (ACS_BULLET));
SetDictInt("ACS_LARROW", (ACS_LARROW));
SetDictInt("ACS_RARROW", (ACS_RARROW));
SetDictInt("ACS_DARROW", (ACS_DARROW));
SetDictInt("ACS_UARROW", (ACS_UARROW));
SetDictInt("ACS_BOARD", (ACS_BOARD));
SetDictInt("ACS_LANTERN", (ACS_LANTERN));
SetDictInt("ACS_BLOCK", (ACS_BLOCK));
#endif And static int
PyCurses_ConvertToCchar_t(PyCursesWindowObject *win, PyObject *obj,
chtype *ch
#ifdef HAVE_NCURSESW
, wchar_t *wch
#endif
) So detecting ncurses's actual include path is necessary. |
This patch does not add /usr/include/ncursesw to the include directories search paths when cross compiling. Restoring the original title. @Chi Hsuan Yen |
no, this is a very wrong simplification. Both gcc and clang offer a method to search for header files and libraries in a target specific location. Please use these options. |
AFAIK there is no target specific location when cross compiling. What are those cross compilation target specific locations according to you ? |
Please open a new issue for the detection of the curses paths. The current issue is about the failure to cross compile _curses when /usr/include/ncursesw is added to these paths. See the original post and the original title. |
@xdegaye: no-path-to-ncursesw.patch fixes a problem yet introducing a new one. With that patch auto-detection of ncurses include files are broken. Now users have to specify the path manually even for native builds. |
This does not make sense, the patch does not change anything for the native builds. |
Sorry I didn't read your patch carefully and it's surprising for me that you didn't remove/modify this line in configure.ac: CPPFLAGS="$CPPFLAGS -I/usr/include/ncursesw" With this line left there, feature detections for _curses are broken as ./configure check against native (/usr/include) headers, whose results make little sense for cross-builds. |
Hum, I did miss that line in configure.ac, thanks for pointing that out. |
New changeset 8c78d844d6f0 by Xavier de Gaye in branch '3.6': New changeset bdf92b4e02f2 by Xavier de Gaye in branch 'default': |
As ncurses-related modules in Python alreadu build fine for Android, I consider the issue resolved. |
no, please don't assume that if it builds for one cross build variant, that it builds for all. re-opening. |
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