Hello. I think https://github.com/python/cpython/pull/23142 changed the behavior of distutils.sysconfig.parse_makefile().

A downstream Fedora report with an affected petsc package: https://bugzilla.redhat.com/show_bug.cgi?id=1959088


Reproducers (DeprecationWarnings removed for readability):


$ cat makefile
ALL: lib

DIRS = ssls asls # isls rscs
LOCDIR = src/tao/complementarity/impls/

include ${PETSC_DIR}/lib/petsc/conf/variables
include ${PETSC_DIR}/lib/petsc/conf/rules
include ${PETSC_DIR}/lib/petsc/conf/test


$ python3.9
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['ssls', 'asls']

$ python3.10
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['ssls', 'asls', '#', 'isls', 'rscs']



And:

$ cat makefile
-include ../../../../petscdir.mk
ALL: lib

LIBBASE  = libpetscksp
DIRS     = cr bcgs bcgsl cg cgs gmres cheby rich lsqr preonly tcqmr tfqmr \
           qcg bicg minres symmlq lcd ibcgs python gcr fcg tsirm fetidp hpddm
LOCDIR   = src/ksp/ksp/impls/

include ${PETSC_DIR}/lib/petsc/conf/variables
include ${PETSC_DIR}/lib/petsc/conf/rules
include ${PETSC_DIR}/lib/petsc/conf/test

$ python3.9
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['cr', 'bcgs', 'bcgsl', 'cg', 'cgs', 'gmres', 'cheby', 'rich', 'lsqr', 'preonly', 'tcqmr', 'tfqmr', 'qcg', 'bicg', 'minres', 'symmlq', 'lcd', 'ibcgs', 'python', 'gcr', 'fcg', 'tsirm', 'fetidp', 'hpddm']

$ python3.10
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['cr', 'bcgs', 'bcgsl', 'cg', 'cgs', 'gmres', 'cheby', 'rich', 'lsqr', 'preonly', 'tcqmr', 'tfqmr', '\\']


And:

$ cat makefile
-include ../../../../petscdir.mk
ALL: lib

LIBBASE  = libpetscksp
DIRS     = jacobi none sor shell bjacobi mg eisens asm ksp composite redundant spai is pbjacobi vpbjacobi ml\
           mat hypre tfs fieldsplit factor galerkin cp wb python \
           chowiluviennacl chowiluviennaclcuda rowscalingviennacl rowscalingviennaclcuda saviennacl saviennaclcuda\
           lsc redistribute gasm svd gamg parms bddc kaczmarz telescope patch lmvm hmg deflation hpddm hara
LOCDIR   = src/ksp/pc/impls/

include ${PETSC_DIR}/lib/petsc/conf/variables
include ${PETSC_DIR}/lib/petsc/conf/rules
include ${PETSC_DIR}/lib/petsc/conf/test

$ python3.9
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['jacobi', 'none', 'sor', 'shell', 'bjacobi', 'mg', 'eisens', 'asm', 'ksp', 'composite', 'redundant', 'spai', 'is', 'pbjacobi', 'vpbjacobi', 'ml', 'mat', 'hypre', 'tfs', 'fieldsplit', 'factor', 'galerkin', 'cp', 'wb', 'python', 'chowiluviennacl', 'chowiluviennaclcuda', 'rowscalingviennacl', 'rowscalingviennaclcuda', 'saviennacl', 'saviennaclcuda', 'lsc', 'redistribute', 'gasm', 'svd', 'gamg', 'parms', 'bddc', 'kaczmarz', 'telescope', 'patch', 'lmvm', 'hmg', 'deflation', 'hpddm', 'hara']

$ python3.10
>>> from distutils.sysconfig import parse_makefile
>>> makevars = parse_makefile('makefile')
>>> makevars.get('DIRS','').split()
['jacobi', 'none', 'sor', 'shell', 'bjacobi', 'mg', 'eisens', 'asm', 'ksp', 'composite', 'redundant', 'spai', 'is', 'pbjacobi', 'vpbjacobi', 'ml\\']