linux: use libedit instead of libreadline

readline is GPL 3.0 licensed. libedit has a more permissive
license.

This commit teaches the Linux build to use libedit instead of
libreadline.

Due to the change, we get a warning at run-time about the
inability to locate the termcap database. There is still more
work to do here. But at least the GPL 3.0 issue is behind us.

Author: indygreg

README.rst

@@ -223,6 +223,9 @@ On macOS, we statically link a ``libedit`` we compile ourselves. We
 dynamically link against ``libncurses``, which is provided by the
 system, typically in ``/usr/lib``.
 
+On Linux, we statically link a ``libedit`` we compile ourselves, which
+is compiled against a ``libncurses`` we build ourselves.
+
 Distribution Format
 ===================
 

cpython-linux/build-cpython.sh

@@ -28,6 +28,14 @@ mv Setup.local Python-${PYTHON_VERSION}/Modules/Setup.local
 
 pushd Python-${PYTHON_VERSION}
 
+# Python supports using libedit instead of readline. But Modules/readline.c
+# has all of this behind ``#ifdef __APPLE__`` instead of a more specific
+# feature flag. All occurrences of __APPLE__ in that file are related to
+# libedit. So we just replace the content. USE_LIBEDIT comes from our
+# static-modules file.
+# TODO make changes upstream to allow libedit to more easily be used
+sed -i s/__APPLE__/USE_LIBEDIT/g Modules/readline.c
+
 # Most bits look at CFLAGS. But setup.py only looks at CPPFLAGS.
 # So we need to set both.
 CFLAGS="-fPIC -I/tools/deps/include -I/tools/deps/include/ncurses"

cpython-linux/build.py

@@ -551,10 +551,11 @@ def build_cpython(client, image, platform):
         install_tools_archive(container, BUILD / ('bzip2-%s.tar' % platform))
         # TODO build against Berkeley DB to avoid GPLv3.
         install_tools_archive(container, BUILD / ('gdbm-%s.tar' % platform))
+        # TODO support libedit/libreadline toggle
+        install_tools_archive(container, BUILD / ('libedit-%s.tar' % platform))
         install_tools_archive(container, BUILD / ('libffi-%s.tar' % platform))
         install_tools_archive(container, BUILD / ('ncurses-%s.tar' % platform))
         install_tools_archive(container, BUILD / ('openssl-%s.tar' % platform))
-        install_tools_archive(container, BUILD / ('readline-%s.tar' % platform))
         install_tools_archive(container, BUILD / ('sqlite-%s.tar' % platform))
         # tk requires a bunch of X11 stuff.
         #install_tools_archive(container, BUILD / ('tcltk-%s.tar' % platform))

cpython-linux/static-modules

@@ -31,5 +31,5 @@ _uuid _uuidmodule.c -I/tools/deps/include/uuid -luuid
 _xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 ossaudiodev ossaudiodev.c
 pyexpat pyexpat.c expat/xmlparse.c expat/xmlrole.c expat/xmltok.c -DHAVE_EXPAT_CONFIG_H=1 -DXML_POOR_ENTROPY=1 -DUSE_PYEXPAT_CAPI -IModules/expat
-readline readline.c -I/tools/deps/include -I/tools/deps/include/ncurses -L/tools/deps/lib -lreadline -lncurses
+readline readline.c -DUSE_LIBEDIT=1 -I/tools/deps/include -I/tools/deps/include/ncurses -L/tools/deps/lib -ledit -lncurses
 xxlimited xxlimited.c -DPy_LIMITED_API=0x03050000