symlink python to python3

[lucize]

@commodo Hi, what is the implication of having python symlinked to python3.8, there are some packages that are searching first for python and they find it in host/bin instead of using hostpkg/bin so any modules needed are searched in host/lib and not found

[commodo]

python being symlinked to python3 should only be important on the target; i'm a bit puzzled as to why it could be an issue on the host-side/build

[lucize]

so for mesa I need python3/mako/host python3/mako will install in ~/hostpkg/lib/python3.8/ mesa and xcb-proto are searching for python, they find it in ~/host/bin (python linked to host python3.7) they are happy that there is a python3.7 but when searching for aditional modules (mako) in this case they search for lib of python3.7 /usr/lib not ~/hostpkg/lib/python3.8

hope you understand the issue

[commodo]

maybe try HOST_PYTHON3_PACKAGE_BUILD_DEPENDS:="mako" before

include ../pypi.mk
include $(INCLUDE_DIR)/package.mk
include ../python3-package.mk

installing python3 packages on the host build is always messy; this mechanism was introduced to help with host issues; it should also guarantee that the proper Python3 is being used;

[lucize]

I think that the configure.ac for the apps is outdated, mesa seems to have been patched it on newer sources, but the question still stands for maybe others, it hurts us to have ~/hostpkg/pyhon symlinked to ~hostpkg/python3.8, hostpkg being searched first

[jefferyto]

The host install of the python3 package does not install a python symlink to $(STAGING_DIR_HOSTPKG)/bin. I don't have a code reference to link to here but if you look in your $(STAGING_DIR_HOSTPKG)/bin you will see a python3 symlink pointing to python3.8 but no python symlink.

(If you are thinking of #11793, that added a symlink for the target package, not host install.)

Also, $(STAGING_DIR)/host/bin is ahead of $(STAGING_DIR_HOSTPKG)/bin in the path when compiling packages. You can see this in TARGET_PATH_PKG, which is exported as PATH during package build.

There is a python symlink in $(STAGING_DIR)/host/bin, that links to your system Python.

You have already described this in https://github.com/openwrt/packages/issues/12082#issuecomment-623967829: mesa is using system Python (python in $(STAGING_DIR)/host/bin), that's why it is Python 3.7 and wants to use /usr/lib), but the mako dependency is installed by host Python (python3 in $(STAGING_DIR_HOSTPKG)/bin) and is installed inside buildroot.

The solution is to tell mesa to use host Python; this is usually done by setting the PYTHON environment variable during configure and/or make (e.g. samba4, uwsgi, libgpiod).

[lucize]

yes, but letting it to use the system python would imply that we have to install the python-dev on the system, this is not available on the build bots, as we don't have python2 anymore is not ok for us to have the link for python as it is now for python3 ? the old configure.ac is searching first for python and then for python3 so like #11793 but for the host install

[jefferyto]

The python symlink in $(STAGING_DIR)/host/bin is added by prereq-build.mk, not us. I presume it exists because scripts in the main repo use python to run their own Python scripts; it doesn't exist to support compiling packages.

As I said, the solution is to tell configure to use host Python, not system Python.

[lucize]

is ok for system to be in $(STAGING_DIR)/host/bin , having the host install in $(STAGING_DIR_HOSTPKG)/bin will let autotools to find the correct version (the host python, not system)

[jefferyto]

If host Python is ahead of system Python in the path, a broken host Python would affect main repo builds.

[lucize]

ok, I understand