toolchain.py

# #
# Copyright 2012-2023 Ghent University
#
# This file is part of EasyBuild,
# originally created by the HPC team of Ghent University (http://ugent.be/hpc/en),
# with support of Ghent University (http://ugent.be/hpc),
# the Flemish Supercomputer Centre (VSC) (https://www.vscentrum.be),
# Flemish Research Foundation (FWO) (http://www.fwo.be/en)
# and the Department of Economy, Science and Innovation (EWI) (http://www.ewi-vlaanderen.be/en).
#
# https://github.com/easybuilders/easybuild
#
# EasyBuild is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation v2.
#
# EasyBuild is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with EasyBuild.  If not, see <http://www.gnu.org/licenses/>.
# #
"""
The toolchain module with the abstract Toolchain class.

Creating a new toolchain should be as simple as possible.

Toolchain terminology
---------------------

Toolchain: group of development related utilities (eg compiler) and libraries (eg MPI, linear algebra)
    -> eg tc=Toolchain()


Toolchain options : options passed to the toolchain through the easyconfig file
    -> eg tc.options

Options : all options passed to an executable
    Flags: specific subset of options, typically involved with compilation
        -> eg tc.variables.CFLAGS
    LinkOptions: specific subset of options, typically involved with linking
        -> eg tc.variables.LIBBLAS

TooclchainVariables: list of environment variables that are set when the toolchain is initialised
           and the toolchain options have been parsed.
    -> eg tc.variables['X'] will be available as os.environ['X']

Authors:

* Stijn De Weirdt (Ghent University)
* Kenneth Hoste (Ghent University)
"""
import copy
import os
import stat
import sys
import tempfile

from easybuild.base import fancylogger
from easybuild.tools.build_log import EasyBuildError, dry_run_msg, print_warning
from easybuild.tools.config import build_option, install_path
from easybuild.tools.environment import setvar
from easybuild.tools.filetools import adjust_permissions, find_eb_script, read_file, which, write_file
from easybuild.tools.module_generator import dependencies_for
from easybuild.tools.modules import get_software_root, get_software_root_env_var_name
from easybuild.tools.modules import get_software_version, get_software_version_env_var_name
from easybuild.tools.systemtools import LINUX, get_os_type
from easybuild.tools.toolchain.options import ToolchainOptions
from easybuild.tools.toolchain.toolchainvariables import ToolchainVariables
from easybuild.tools.utilities import nub, trace_msg


_log = fancylogger.getLogger('tools.toolchain', fname=False)

# name/version for dummy toolchain
# if name==DUMMY_TOOLCHAIN_NAME and version==DUMMY_TOOLCHAIN_VERSION, do not load dependencies
# NOTE: use of 'dummy' toolchain is deprecated, replaced by 'system' toolchain (which always loads dependencies)
DUMMY_TOOLCHAIN_NAME = 'dummy'
DUMMY_TOOLCHAIN_VERSION = 'dummy'

SYSTEM_TOOLCHAIN_NAME = 'system'

CCACHE = 'ccache'
F90CACHE = 'f90cache'

RPATH_WRAPPERS_SUBDIR = 'rpath_wrappers'

# available capabilities of toolchains
# values match method names supported by Toolchain class (except for 'cuda')
TOOLCHAIN_CAPABILITY_BLAS_FAMILY = 'blas_family'
TOOLCHAIN_CAPABILITY_COMP_FAMILY = 'comp_family'
TOOLCHAIN_CAPABILITY_CUDA = 'cuda'
TOOLCHAIN_CAPABILITY_LAPACK_FAMILY = 'lapack_family'
TOOLCHAIN_CAPABILITY_MPI_FAMILY = 'mpi_family'
TOOLCHAIN_CAPABILITIES = [
    TOOLCHAIN_CAPABILITY_BLAS_FAMILY,
    TOOLCHAIN_CAPABILITY_COMP_FAMILY,
    TOOLCHAIN_CAPABILITY_CUDA,
    TOOLCHAIN_CAPABILITY_LAPACK_FAMILY,
    TOOLCHAIN_CAPABILITY_MPI_FAMILY,
]


def is_system_toolchain(tc_name):
    """Return whether toolchain with specified name is a system toolchain or not."""
    return tc_name in [DUMMY_TOOLCHAIN_NAME, SYSTEM_TOOLCHAIN_NAME]


def env_vars_external_module(name, version, metadata):
    """
    Determine $EBROOT* and/or $EBVERSION* environment variables that can be set for external module,
    based on the provided name, version and metadata.
    """
    env_vars = {}

    # define $EBROOT env var for install prefix, picked up by get_software_root
    prefix = metadata.get('prefix')
    if prefix is not None:
        # the prefix can be specified in a number of ways
        # * name of environment variable (+ optional relative path to combine it with; format: <name>/<relpath>
        # * filepath (assumed if environment variable is not defined)
        parts = prefix.split(os.path.sep)
        env_var = parts[0]
        if env_var in os.environ:
            prefix = os.environ[env_var]
            rel_path = os.path.sep.join(parts[1:])
            if rel_path:
                prefix = os.path.join(prefix, rel_path, '')

            _log.debug("Derived prefix for software named %s from $%s (rel path: %s): %s",
                       name, env_var, rel_path, prefix)
        else:
            _log.debug("Using specified path as prefix for software named %s: %s", name, prefix)

        env_vars[get_software_root_env_var_name(name)] = prefix

    # define $EBVERSION env var for software version, picked up by get_software_version
    if version is not None:
        env_vars[get_software_version_env_var_name(name)] = version

    return env_vars


class Toolchain(object):
    """General toolchain class"""

    OPTIONS_CLASS = ToolchainOptions
    VARIABLES_CLASS = ToolchainVariables

    NAME = None
    VERSION = None
    SUBTOOLCHAIN = None
    TOOLCHAIN_FAMILY = None

    # list of class 'constants' that should be restored for every new instance of this class
    CLASS_CONSTANTS_TO_RESTORE = None
    CLASS_CONSTANT_COPIES = {}

    # class method
    def _is_toolchain_for(cls, name):
        """see if this class can provide support for toolchain named name"""
        # TODO report later in the initialization the found version
        if name:
            if hasattr(cls, 'NAME') and name == cls.NAME:
                return True
            else:
                return False
        else:
            # is no name is supplied, check whether class can be used as a toolchain
            return hasattr(cls, 'NAME') and cls.NAME

    _is_toolchain_for = classmethod(_is_toolchain_for)

    def __init__(self, name=None, version=None, mns=None, class_constants=None, tcdeps=None, modtool=None,
                 hidden=False):
        """
        Toolchain constructor.

        :param name: toolchain name
        :param version: toolchain version
        :param mns: module naming scheme to use
        :param class_constants: toolchain 'constants' to define
        :param tcdeps: list of toolchain 'dependencies' (i.e., the toolchain components)
        :param modtool: ModulesTool instance to use
        :param hidden: bool indicating whether toolchain is hidden or not
        """
        self.base_init()

        self.dependencies = []
        self.toolchain_dep_mods = []
        self.cached_compilers = set()

        if name is None:
            name = self.NAME
        if name is None:
            raise EasyBuildError("Toolchain init: no name provided")
        self.name = name
        if self.name == DUMMY_TOOLCHAIN_NAME:
            self.log.deprecated("Use of 'dummy' toolchain is deprecated, use 'system' toolchain instead", '5.0',
                                silent=build_option('silent'))
            self.name = SYSTEM_TOOLCHAIN_NAME

        if version is None:
            version = self.VERSION
        if version is None:
            raise EasyBuildError("Toolchain init: no version provided")
        self.version = version

        self.modules = []
        self.vars = None

        self._init_class_constants(class_constants)

        self.tcdeps = tcdeps

        # toolchain instances are created before initiating build options sometimes, e.g. for --list-toolchains
        self.dry_run = build_option('extended_dry_run', default=False)
        hidden_toolchains = build_option('hide_toolchains', default=None) or []
        self.hidden = hidden or (name in hidden_toolchains)

        self.modules_tool = modtool

        self.use_rpath = False

        self.mns = mns
        self.mod_full_name = None
        self.mod_short_name = None
        self.init_modpaths = None
        if not self.is_system_toolchain():
            # sometimes no module naming scheme class instance can/will be provided, e.g. with --list-toolchains
            if self.mns is not None:
                tc_dict = self.as_dict()
                self.mod_full_name = self.mns.det_full_module_name(tc_dict)
                self.mod_short_name = self.mns.det_short_module_name(tc_dict)
                self.init_modpaths = self.mns.det_init_modulepaths(tc_dict)

    def is_system_toolchain(self):
        """Return boolean to indicate whether this toolchain is a system(/dummy) toolchain."""
        return is_system_toolchain(self.name)

    def set_minimal_build_env(self):
        """Set up a minimal build environment, by setting (only) the $CC and $CXX environment variables."""

        # this is only relevant when using a system toolchain,
        # for proper toolchains these variables will get set via the call to set_variables()

        minimal_build_env_raw = build_option('minimal_build_env')

        minimal_build_env = {}
        for key_val in minimal_build_env_raw.split(','):
            parts = key_val.split(':')
            if len(parts) == 2:
                key, val = parts
                minimal_build_env[key] = val
            else:
                raise EasyBuildError("Incorrect mapping in --minimal-build-env value: '%s'", key_val)

        env_vars = {}
        for key, val in minimal_build_env.items():
            # for key environment variables like $CC and $CXX we are extra careful,
            # by making sure the specified command is actually available
            if key in ['CC', 'CXX']:
                warning_msg = None
                if os.path.isabs(val):
                    if os.path.exists(val):
                        self.log.info("Specified path for $%s exists: %s", key, val)
                        env_vars.update({key: val})
                    else:
                        warning_msg = "Specified path '%s' does not exist"
                else:
                    cmd_path = which(val)
                    if cmd_path:
                        self.log.info("Found compiler command %s at %s, so setting $%s in minimal build environment",
                                      val, cmd_path, key)
                        env_vars.update({key: val})
                    else:
                        warning_msg = "'%s' command not found in $PATH" % val

                if warning_msg:
                    print_warning(warning_msg + ", not setting $%s in minimal build environment" % key, log=self.log)
            else:
                # no checking for environment variables other than $CC or $CXX
                env_vars.update({key: val})

        # set specified environment variables, but print a warning
        # if we're redefining anything that was already set to a *different* value
        for key, new_value in env_vars.items():
            curr_value = os.getenv(key)
            if curr_value and curr_value != new_value:
                print_warning("$%s was defined as '%s', but is now set to '%s' in minimal build environment",
                              key, curr_value, new_value)
            setvar(key, new_value)

    def base_init(self):
        """Initialise missing class attributes (log, options, variables)."""
        if not hasattr(self, 'log'):
            self.log = fancylogger.getLogger(self.__class__.__name__, fname=False)

        if not hasattr(self, 'options'):
            self.options = self.OPTIONS_CLASS()

        if not hasattr(self, 'variables'):
            self.variables_init()

    def variables_init(self):
        """Initialise toolchain variables."""
        self.variables = self.VARIABLES_CLASS()
        if hasattr(self, 'LINKER_TOGGLE_START_STOP_GROUP'):
            self.variables.LINKER_TOGGLE_START_STOP_GROUP = self.LINKER_TOGGLE_START_STOP_GROUP
        if hasattr(self, 'LINKER_TOGGLE_STATIC_DYNAMIC'):
            self.variables.LINKER_TOGGLE_STATIC_DYNAMIC = self.LINKER_TOGGLE_STATIC_DYNAMIC

    def _init_class_constants(self, class_constants):
        """Initialise class 'constants'."""
        # make sure self.CLASS_CONSTANTS_TO_RESTORE is initialised
        if class_constants is None:
            self.CLASS_CONSTANTS_TO_RESTORE = []
        else:
            self.CLASS_CONSTANTS_TO_RESTORE = class_constants[:]

        self._copy_class_constants()
        self._restore_class_constants()

    def _copy_class_constants(self):
        """Copy class constants that needs to be restored again when a new instance is created."""
        # this only needs to be done the first time (for this class, taking inheritance into account is key)
        key = self.__class__
        if key not in self.CLASS_CONSTANT_COPIES:
            self.CLASS_CONSTANT_COPIES[key] = {}
            for cst in self.CLASS_CONSTANTS_TO_RESTORE:
                if hasattr(self, cst):
                    self.CLASS_CONSTANT_COPIES[key][cst] = copy.deepcopy(getattr(self, cst))
                else:
                    raise EasyBuildError("Class constant '%s' to be restored does not exist in %s", cst, self)

            self.log.devel("Copied class constants: %s", self.CLASS_CONSTANT_COPIES[key])

    def _restore_class_constants(self):
        """Restored class constants that need to be restored when a new instance is created."""
        key = self.__class__
        for cst in self.CLASS_CONSTANT_COPIES[key]:
            newval = copy.deepcopy(self.CLASS_CONSTANT_COPIES[key][cst])
            if hasattr(self, cst):
                self.log.devel("Restoring class constant '%s' to %s (was: %s)", cst, newval, getattr(self, cst))
            else:
                self.log.devel("Restoring (currently undefined) class constant '%s' to %s", cst, newval)

            setattr(self, cst, newval)

    def get_variable(self, name, typ=str):
        """Get value for specified variable.
        typ: indicates what type of return value is expected"""

        if typ == str:
            res = str(self.variables.get(name, ''))

        elif typ == list:
            if name in self.variables:
                res = self.variables[name].flatten()
            else:
                res = []
        else:
            raise EasyBuildError("get_variable: Don't know how to create value of type %s.", typ)

        return res

    def set_variables(self):
        """Do nothing? Everything should have been set by others
            Needs to be defined for super() relations
        """
        if self.options.option('packed-linker-options'):
            self.log.devel("set_variables: toolchain variables. packed-linker-options.")
            self.variables.try_function_on_element('set_packed_linker_options')
        self.log.devel("set_variables: toolchain variables. Do nothing.")

    def generate_vars(self):
        """Convert the variables in simple vars"""
        self.vars = {}
        for k, v in self.variables.items():
            self.vars[k] = str(v)

    def show_variables(self, offset='', sep='\n', verbose=False):
        """Pretty print the variables"""
        if self.vars is None:
            self.generate_vars()

        var_names = sorted(self.variables.keys())
        res = []
        for v in var_names:
            res.append("%s=%s" % (v, self.variables[v]))
            if verbose:
                res.append("# type %s" % (type(self.variables[v])))
                res.append("# %s" % (self.variables[v].show_el()))
                res.append("# repr %s" % (self.variables[v].__repr__()))

        if offset is None:
            offset = ''
        txt = sep.join(["%s%s" % (offset, x) for x in res])
        self.log.debug("show_variables:\n%s", txt)
        return txt

    def get_software_root(self, names):
        """Try to get the software root for all names"""
        return self._get_software_multiple(names, self._get_software_root)

    def get_software_version(self, names, required=True):
        """Try to get the software version for all names"""
        return self._get_software_multiple(names, self._get_software_version, required=required)

    def _get_software_multiple(self, names, function, required=True):
        """Execute function of each of names"""
        if isinstance(names, (str,)):
            names = [names]
        res = []
        for name in names:
            res.append(function(name, required=required))
        return res

    def _get_software_root(self, name, required=True):
        """Try to get the software root for name"""
        root = get_software_root(name)
        if root is None:
            if required:
                raise EasyBuildError("get_software_root software root for %s was not found in environment", name)
        else:
            self.log.debug("get_software_root software root %s for %s was found in environment", root, name)
        return root

    def _get_software_version(self, name, required=True):
        """Try to get the software version for name"""
        version = get_software_version(name)
        if version is None:
            if required:
                raise EasyBuildError("get_software_version software version for %s was not found in environment", name)
        else:
            self.log.debug("get_software_version software version %s for %s was found in environment", version, name)

        return version

    def as_dict(self, name=None, version=None):
        """Return toolchain specification as a dictionary."""
        if name is None:
            name = self.name
        if version is None:
            version = self.version
        return {
            'name': name,
            'version': version,
            'toolchain': {'name': SYSTEM_TOOLCHAIN_NAME, 'version': ''},
            'versionsuffix': '',
            'parsed': True,  # pretend this is a parsed easyconfig file, as may be required by det_short_module_name
            'hidden': self.hidden,
            'full_mod_name': self.mod_full_name,
            'short_mod_name': self.mod_short_name,
            SYSTEM_TOOLCHAIN_NAME: True,
        }

    def det_short_module_name(self):
        """Determine module name for this toolchain."""
        if self.mod_short_name is None:
            raise EasyBuildError("Toolchain module name was not set yet")
        return self.mod_short_name

    def _toolchain_exists(self):
        """
        Verify if there exists a toolchain by this name and version
        """
        # short-circuit to returning module name for this (non-system) toolchain
        if self.is_system_toolchain():
            self.log.devel("_toolchain_exists: system toolchain always exists, returning True")
            return True
        else:
            if self.mod_short_name is None:
                raise EasyBuildError("Toolchain module name was not set yet")
            # check whether a matching module exists if self.mod_short_name contains a module name
            return self.modules_tool.exist([self.mod_full_name], skip_avail=True)[0]

    def set_options(self, options):
        """ Process toolchain options """
        for opt in options.keys():
            # Only process supported opts
            if opt in self.options:
                self.options[opt] = options[opt]
            else:
                # used to be warning, but this is a severe error imho
                known_opts = ','.join(self.options.keys())
                raise EasyBuildError("Undefined toolchain option %s specified (known options: %s)", opt, known_opts)

    def get_dependency_version(self, dependency):
        """ Generate a version string for a dependency on a module using this toolchain """
        # add toolchain to version string (only for non-system toolchain)
        if self.is_system_toolchain():
            toolchain = ''
        else:
            toolchain = '-%s-%s' % (self.name, self.version)

        # check if dependency is independent of toolchain (i.e. whether is was built with system compiler)
        if SYSTEM_TOOLCHAIN_NAME in dependency and dependency[SYSTEM_TOOLCHAIN_NAME]:
            toolchain = ''

        suffix = dependency.get('versionsuffix', '')

        if 'version' in dependency:
            version = ''.join([dependency['version'], toolchain, suffix])
            self.log.devel("get_dependency_version: version in dependency return %s", version)
            return version
        else:
            toolchain_suffix = ''.join([toolchain, suffix])
            matches = self.modules_tool.available(dependency['name'], toolchain_suffix)
            # Find the most recent (or default) one
            if len(matches) > 0:
                version = matches[-1][-1]
                self.log.devel("get_dependency_version: version not in dependency return %s", version)
                return
            else:
                raise EasyBuildError("No toolchain version for dependency name %s (suffix %s) found",
                                     dependency['name'], toolchain_suffix)

    def _check_dependencies(self, dependencies):
        """ Verify if the given dependencies exist and return them """
        self.log.debug("_check_dependencies: adding toolchain dependencies %s", dependencies)

        # use *full* module name to check existence of dependencies, since the modules may not be available in the
        # current $MODULEPATH without loading the prior dependencies in a module hierarchy
        # (e.g. OpenMPI module may only be available after loading GCC module);
        # when actually loading the modules for the dependencies, the *short* module name is used,
        # see _load_dependencies_modules()
        dep_mod_names = [dep['full_mod_name'] for dep in dependencies]

        # check whether modules exist
        self.log.debug("_check_dependencies: MODULEPATH: %s", os.environ['MODULEPATH'])
        if self.dry_run:
            deps_exist = [True] * len(dep_mod_names)
        else:
            deps_exist = self.modules_tool.exist(dep_mod_names)

        missing_dep_mods = []
        deps = []
        for dep, dep_mod_name, dep_exists in zip(dependencies, dep_mod_names, deps_exist):
            if dep_exists:
                deps.append(dep)
                self.log.devel("_check_dependencies: added toolchain dependency %s", str(dep))
            elif dep['external_module']:
                # external modules may be organised hierarchically,
                # so not all modules may be directly available for loading;
                # we assume here that the required modules are either provided by the toolchain,
                # or are listed earlier as dependency
                # examples from OpenHPC:
                # - openmpi3 module provided by OpenHPC requires that gnu7, gnu8 or intel module is loaded first
                # - fftw module provided by OpenHPC requires that compiler + MPI module are loaded first
                self.log.info("Assuming non-visible external module %s is available", dep['full_mod_name'])
                deps.append(dep)
            else:
                missing_dep_mods.append(dep_mod_name)

        if missing_dep_mods:
            raise EasyBuildError("Missing modules for dependencies (use --robot?): %s", ', '.join(missing_dep_mods))

        return deps

    def add_dependencies(self, dependencies):
        """
        [DEPRECATED] Verify if the given dependencies exist, and return them.

        This method is deprecated.
        You should pass the dependencies to the 'prepare' method instead, via the 'deps' named argument.
        """
        self.log.deprecated("use of 'Toolchain.add_dependencies' method", '4.0')
        self.dependencies = self._check_dependencies(dependencies)

    def is_required(self, name):
        """Determine whether this is a required toolchain element."""
        # default: assume every element is required
        return True

    def definition(self):
        """
        Determine toolchain elements for given Toolchain instance.
        """
        var_suff = '_MODULE_NAME'
        tc_elems = {}
        for var in dir(self):
            if var.endswith(var_suff) and getattr(self, var) is not None:
                tc_elems.update({var[:-len(var_suff)]: getattr(self, var)})

        self.log.debug("Toolchain definition for %s: %s", self.as_dict(), tc_elems)
        return tc_elems

    def is_dep_in_toolchain_module(self, name):
        """Check whether a specific software name is listed as a dependency in the module for this toolchain."""
        return any(map(lambda m: self.mns.is_short_modname_for(m, name), self.toolchain_dep_mods))

    def _simulated_load_dependency_module(self, name, version, metadata, verbose=False):
        """
        Set environment variables picked up by utility functions for dependencies specified as external modules.

        :param name: software name
        :param version: software version
        :param metadata: dictionary with software metadata ('prefix' for software installation prefix)
        """

        self.log.debug("Defining $EB* environment variables for software named %s", name)

        env_vars = env_vars_external_module(name, version, metadata)
        for key in env_vars:
            setvar(key, env_vars[key], verbose=verbose)

    def _load_toolchain_module(self, silent=False):
        """Load toolchain module."""

        tc_mod = self.det_short_module_name()

        if self.dry_run:
            dry_run_msg("Loading toolchain module...\n", silent=silent)

            # load toolchain module, or simulate load of toolchain components if it is not available
            if self.modules_tool.exist([tc_mod], skip_avail=True)[0]:
                self.modules_tool.load([tc_mod])
                dry_run_msg("module load %s" % tc_mod, silent=silent)
            else:
                # first simulate loads for toolchain dependencies, if required information is available
                if self.tcdeps is not None:
                    for tcdep in self.tcdeps:
                        modname = tcdep['short_mod_name']
                        dry_run_msg("module load %s [SIMULATED]" % modname, silent=silent)
                        # 'use '$EBROOTNAME' as value for dep install prefix (looks nice in dry run output)
                        deproot = '$%s' % get_software_root_env_var_name(tcdep['name'])
                        self._simulated_load_dependency_module(tcdep['name'], tcdep['version'], {'prefix': deproot})

                dry_run_msg("module load %s [SIMULATED]" % tc_mod, silent=silent)
                # use name of $EBROOT* env var as value for $EBROOT* env var (results in sensible dry run output)
                tcroot = '$%s' % get_software_root_env_var_name(self.name)
                self._simulated_load_dependency_module(self.name, self.version, {'prefix': tcroot})
        else:
            # make sure toolchain is available using short module name by running 'module use' on module path subdir
            if self.init_modpaths:
                mod_path_suffix = build_option('suffix_modules_path')
                for modpath in self.init_modpaths:
                    modpath = os.path.join(install_path('mod'), mod_path_suffix, modpath)
                    if os.path.exists(modpath):
                        self.modules_tool.prepend_module_path(modpath)

            # load modules for all dependencies
            self.log.debug("Loading module for toolchain: %s", tc_mod)
            trace_msg("loading toolchain module: " + tc_mod)
            self.modules_tool.load([tc_mod])

        # append toolchain module to list of modules
        self.modules.append(tc_mod)

    def _load_dependencies_modules(self, silent=False):
        """Load modules for dependencies, and handle special cases like external modules."""
        dep_mods = [dep['short_mod_name'] for dep in self.dependencies]

        if self.dry_run:
            dry_run_msg("\nLoading modules for dependencies...\n", silent=silent)

            mods_exist = self.modules_tool.exist(dep_mods)

            # load available modules for dependencies, simulate load for others
            for dep, dep_mod_exists in zip(self.dependencies, mods_exist):
                mod_name = dep['short_mod_name']
                if dep_mod_exists:
                    self.modules_tool.load([mod_name])
                    dry_run_msg("module load %s" % mod_name, silent=silent)
                else:
                    dry_run_msg("module load %s [SIMULATED]" % mod_name, silent=silent)
                    # 'use '$EBROOTNAME' as value for dep install prefix (looks nice in dry run output)
                    if not dep['external_module']:
                        deproot = '$%s' % get_software_root_env_var_name(dep['name'])
                        self._simulated_load_dependency_module(dep['name'], dep['version'], {'prefix': deproot})
        else:
            # load modules for all dependencies
            self.log.debug("Loading modules for dependencies: %s", dep_mods)
            self.modules_tool.load(dep_mods)

            if self.dependencies:
                build_dep_mods = [dep['short_mod_name'] for dep in self.dependencies if dep['build_only']]
                if build_dep_mods:
                    trace_msg("loading modules for build dependencies:")
                    for dep_mod in build_dep_mods:
                        trace_msg(' * ' + dep_mod)
                else:
                    trace_msg("(no build dependencies specified)")

                run_dep_mods = [dep['short_mod_name'] for dep in self.dependencies if not dep['build_only']]
                if run_dep_mods:
                    trace_msg("loading modules for (runtime) dependencies:")
                    for dep_mod in run_dep_mods:
                        trace_msg(' * ' + dep_mod)
                else:
                    trace_msg("(no (runtime) dependencies specified)")

        # append dependency modules to list of modules
        self.modules.extend(dep_mods)

        # define $EBROOT* and $EBVERSION* for external modules, if metadata is available
        for dep in [d for d in self.dependencies if d['external_module']]:
            mod_name = dep['full_mod_name']
            metadata = dep['external_module_metadata']
            self.log.debug("Metadata for external module %s: %s", mod_name, metadata)

            names = metadata.get('name', [])
            versions = metadata.get('version', [None] * len(names))
            self.log.debug("Defining $EB* environment variables for external module %s using names %s, versions %s",
                           mod_name, names, versions)

            for name, version in zip(names, versions):
                self._simulated_load_dependency_module(name, version, metadata, verbose=True)

    def _load_modules(self, silent=False):
        """Load modules for toolchain and dependencies."""
        if self.modules_tool is None:
            raise EasyBuildError("No modules tool defined in Toolchain instance.")

        if not self._toolchain_exists() and not self.dry_run:
            raise EasyBuildError("No module found for toolchain: %s", self.mod_short_name)

        if self.is_system_toolchain():
            self.log.info("Loading dependencies using system toolchain...")
            self._load_dependencies_modules(silent=silent)
        else:
            # load the toolchain and dependencies modules
            self.log.debug("Loading toolchain module and dependencies...")
            self._load_toolchain_module(silent=silent)
            self._load_dependencies_modules(silent=silent)

        # include list of loaded modules in dry run output
        if self.dry_run:
            loaded_mods = self.modules_tool.list()
            dry_run_msg("\nFull list of loaded modules:", silent=silent)
            if loaded_mods:
                for i, mod_name in enumerate([m['mod_name'] for m in loaded_mods]):
                    dry_run_msg("  %d) %s" % (i + 1, mod_name), silent=silent)
            else:
                dry_run_msg("  (none)", silent=silent)
            dry_run_msg('', silent=silent)

    def _verify_toolchain(self):
        """Verify toolchain: check toolchain definition against dependencies of toolchain module."""
        # determine direct toolchain dependencies
        mod_name = self.det_short_module_name()
        self.toolchain_dep_mods = dependencies_for(mod_name, self.modules_tool, depth=0)
        self.log.debug("List of toolchain dependencies from toolchain module: %s", self.toolchain_dep_mods)

        # only retain names of toolchain elements, excluding toolchain name
        toolchain_definition = set([e for es in self.definition().values() for e in es if not e == self.name])

        # filter out optional toolchain elements if they're not used in the module
        for elem_name in toolchain_definition.copy():
            if self.is_required(elem_name) or self.is_dep_in_toolchain_module(elem_name):
                continue
            # not required and missing: remove from toolchain definition
            self.log.debug("Removing %s from list of optional toolchain elements.", elem_name)
            toolchain_definition.remove(elem_name)

        self.log.debug("List of toolchain elements from toolchain definition: %s", toolchain_definition)

        if all(map(self.is_dep_in_toolchain_module, toolchain_definition)):
            self.log.info("List of toolchain dependency modules and toolchain definition match!")
        else:
            raise EasyBuildError("List of toolchain dependency modules and toolchain definition do not match "
                                 "(found %s vs expected %s)", self.toolchain_dep_mods, toolchain_definition)

    def symlink_commands(self, paths):
        """
        Create a symlink for each command to binary/script at specified path.

        :param paths: dictionary containing one or mappings, each one specified as a tuple:
                      (<path/to/script>, <list of commands to symlink to the script>)
        """
        symlink_dir = tempfile.mkdtemp()

        # prepend location to symlinks to $PATH
        setvar('PATH', '%s:%s' % (symlink_dir, os.getenv('PATH')))

        for (path, cmds) in paths.values():
            for cmd in cmds:
                cmd_s = os.path.join(symlink_dir, cmd)
                if not os.path.exists(cmd_s):
                    try:
                        os.symlink(path, cmd_s)
                    except OSError as err:
                        raise EasyBuildError("Failed to symlink %s to %s: %s", path, cmd_s, err)

                cmd_path = which(cmd)
                self.log.debug("which(%s): %s -> %s", cmd, cmd_path, os.path.realpath(cmd_path))

            self.log.info("Commands symlinked to %s via %s: %s", path, symlink_dir, ', '.join(cmds))

    def compilers(self):
        """Return list of relevant compilers for this toolchain"""

        if self.is_system_toolchain():
            c_comps = ['gcc', 'g++']
            fortran_comps = ['gfortran']
        else:
            c_comps = [self.COMPILER_CC, self.COMPILER_CXX]
            fortran_comps = [self.COMPILER_F77, self.COMPILER_F90, self.COMPILER_FC]

        return (c_comps, fortran_comps)

    def is_deprecated(self):
        """Return whether or not this toolchain is deprecated."""
        return False

    def reset(self):
        """Reset this toolchain instance."""
        self.variables_init()

    def prepare(self, onlymod=None, deps=None, silent=False, loadmod=True,
                rpath_filter_dirs=None, rpath_include_dirs=None):
        """
        Prepare a set of environment parameters based on name/version of toolchain
        - load modules for toolchain and dependencies
        - generate extra variables and set them in the environment

        :param deps: list of dependencies
        :param onlymod: boolean/string to indicate if the toolchain should only load the environment
                         with module (True) or also set all other variables (False) like compiler CC etc
                         (If string: comma separated list of variables that will be ignored).
        :param silent: keep quiet, or not (mostly relates to extended dry run output)
        :param loadmod: whether or not to (re)load the toolchain module, and the modules for the dependencies
        :param rpath_filter_dirs: extra directories to include in RPATH filter (e.g. build dir, tmpdir, ...)
        :param rpath_include_dirs: extra directories to include in RPATH
        """

        # take into account --sysroot configuration setting
        self.handle_sysroot()

        # do all dependencies have a toolchain version?
        if deps is None:
            deps = []
        self.dependencies = self._check_dependencies(deps)
        if not len(deps) == len(self.dependencies):
            self.log.debug("dep %s (%s)" % (len(deps), deps))
            self.log.debug("tc.dep %s (%s)" % (len(self.dependencies), self.dependencies))
            raise EasyBuildError('Not all dependencies have a matching toolchain version')

        if loadmod:
            self._load_modules(silent=silent)

        if self.is_system_toolchain():

            # define minimal build environment when using system toolchain;
            # this is mostly done to try controlling which compiler commands are being used,
            # cfr. https://github.com/easybuilders/easybuild-framework/issues/3398
            self.set_minimal_build_env()

        else:
            trace_msg("defining build environment for %s/%s toolchain" % (self.name, self.version))

            if not self.dry_run:
                self._verify_toolchain()

            # Generate the variables to be set
            self.set_variables()

            # set the variables
            # onlymod can be comma-separated string of variables not to be set
            if onlymod is True:
                self.log.debug("prepare: do not set additional variables onlymod=%s", onlymod)
                self.generate_vars()
            else:
                self.log.debug("prepare: set additional variables onlymod=%s", onlymod)

                # add LDFLAGS and CPPFLAGS from dependencies to self.vars
                self._add_dependency_variables()
                self.generate_vars()
                self._setenv_variables(onlymod, verbose=not silent)

        # consider f90cache first, since ccache can also wrap Fortran compilers
        for cache_tool in [F90CACHE, CCACHE]:
            if build_option('use_%s' % cache_tool):
                self.prepare_compiler_cache(cache_tool)

        if build_option('rpath'):
            if self.options.get('rpath', True):
                self.prepare_rpath_wrappers(rpath_filter_dirs, rpath_include_dirs)
                self.use_rpath = True
            else:
                self.log.info("Not putting RPATH wrappers in place, disabled via 'rpath' toolchain option")

    def comp_cache_compilers(self, cache_tool):
        """
        Determine list of relevant compilers for specified compiler caching tool.
        :param cache_tool: name of compiler caching tool
        :return: list of names of relevant compilers
        """
        c_comps, fortran_comps = self.compilers()

        if cache_tool == CCACHE:
            # some version of ccache support caching of Fortran compilations,
            # but it doesn't work with Fortran modules (https://github.com/ccache/ccache/issues/342),
            # and support was dropped in recent ccache versions;
            # as a result, we only use ccache for C/C++ compilers
            comps = c_comps
        elif cache_tool == F90CACHE:
            comps = fortran_comps
        else:
            raise EasyBuildError("Uknown compiler caching tool specified: %s", cache_tool)

        # filter out compilers that are already cached;
        # Fortran compilers could already be cached by f90cache when preparing for ccache
        for comp in comps[:]:
            if comp in self.cached_compilers:
                self.log.debug("Not caching compiler %s, it's already being cached", comp)
                comps.remove(comp)

        self.log.info("Using %s for these compiler commands: %s", cache_tool, ', '.join(comps))

        return comps

    def prepare_compiler_cache(self, cache_tool):
        """
        Prepare for using specified compiler caching tool (e.g., ccache, f90cache)

        :param cache_tool: name of compiler caching tool to prepare for
        """
        compilers = self.comp_cache_compilers(cache_tool)
        self.log.debug("Using compiler cache tool '%s' for compilers: %s", cache_tool, compilers)

        # set paths that should be used by compiler caching tool
        comp_cache_path = build_option('use_%s' % cache_tool)
        setvar('%s_DIR' % cache_tool.upper(), comp_cache_path)
        setvar('%s_TEMPDIR' % cache_tool.upper(), tempfile.mkdtemp())

        cache_path = which(cache_tool)
        if cache_path is None:
            raise EasyBuildError("%s binary not found in $PATH, required by --use-ccache", cache_tool)
        else:
            self.symlink_commands({cache_tool: (cache_path, compilers)})

        self.cached_compilers.update(compilers)
        self.log.debug("Cached compilers (after preparing for %s): %s", cache_tool, self.cached_compilers)

    @staticmethod
    def is_rpath_wrapper(path):
        """
        Check whether command at specified location already is an RPATH wrapper script rather than the actual command
        """
        in_rpath_wrappers_dir = os.path.basename(os.path.dirname(os.path.dirname(path))) == RPATH_WRAPPERS_SUBDIR
        # need to use binary mode to read the file, since it may be an actual compiler command (which is a binary file)
        calls_rpath_args = b'rpath_args.py $CMD' in read_file(path, mode='rb')
        return in_rpath_wrappers_dir and calls_rpath_args

    def prepare_rpath_wrappers(self, rpath_filter_dirs=None, rpath_include_dirs=None):
        """
        Put RPATH wrapper script in place for compiler and linker commands

        :param rpath_filter_dirs: extra directories to include in RPATH filter (e.g. build dir, tmpdir, ...)
        """
        if get_os_type() == LINUX:
            self.log.info("Putting RPATH wrappers in place...")
        else:
            raise EasyBuildError("RPATH linking is currently only supported on Linux")

        if rpath_filter_dirs is None:
            rpath_filter_dirs = []

        # always include filter for 'stubs' library directory,
        # cfr. https://github.com/easybuilders/easybuild-framework/issues/2683
        # (since CUDA 11.something the stubs are in $EBROOTCUDA/stubs/lib64)
        lib_stubs_patterns = ['.*/lib(64)?/stubs/?', '.*/stubs/lib(64)?/?']
        for lib_stubs_pattern in lib_stubs_patterns:
            if lib_stubs_pattern not in rpath_filter_dirs:
                rpath_filter_dirs.append(lib_stubs_pattern)

        # directory where all wrappers will be placed
        wrappers_dir = os.path.join(tempfile.mkdtemp(), RPATH_WRAPPERS_SUBDIR)

        # must also wrap compilers commands, required e.g. for Clang ('gcc' on OS X)?
        c_comps, fortran_comps = self.compilers()

        rpath_args_py = find_eb_script('rpath_args.py')
        rpath_wrapper_template = find_eb_script('rpath_wrapper_template.sh.in')

        # figure out list of patterns to use in rpath filter
        rpath_filter = build_option('rpath_filter')
        if rpath_filter is None:
            rpath_filter = ['/lib.*', '/usr.*']
            self.log.debug("No general RPATH filter specified, falling back to default: %s", rpath_filter)
        rpath_filter = ','.join(rpath_filter + ['%s.*' % d for d in rpath_filter_dirs])
        self.log.debug("Combined RPATH filter: '%s'", rpath_filter)

        rpath_include = ','.join(rpath_include_dirs or [])
        self.log.debug("Combined RPATH include paths: '%s'", rpath_include)

        # create wrappers
        for cmd in nub(c_comps + fortran_comps + ['ld', 'ld.gold', 'ld.bfd']):
            # Not all toolchains have fortran compilers (e.g. Clang), in which case they are 'None'
            if cmd is None:
                continue
            orig_cmd = which(cmd)

            if orig_cmd:
                # bail out early if command already is a wrapped;
                # this may occur when building extensions
                if self.is_rpath_wrapper(orig_cmd):
                    self.log.info("%s already seems to be an RPATH wrapper script, not wrapping it again!", orig_cmd)
                    continue

                # determine location for this wrapper
                # each wrapper is placed in its own subdirectory to enable $PATH filtering per wrapper separately
                # avoid '+' character in directory name (for example with 'g++' command), which can cause trouble
                # (see https://github.com/easybuilders/easybuild-easyconfigs/issues/7339)
                wrapper_dir_name = '%s_wrapper' % cmd.replace('+', 'x')
                wrapper_dir = os.path.join(wrappers_dir, wrapper_dir_name)

                cmd_wrapper = os.path.join(wrapper_dir, cmd)

                # make *very* sure we don't wrap around ourselves and create a fork bomb...
                if os.path.exists(cmd_wrapper) and os.path.exists(orig_cmd) and os.path.samefile(orig_cmd, cmd_wrapper):
                    raise EasyBuildError("Refusing the create a fork bomb, which(%s) == %s", cmd, orig_cmd)

                # enable debug mode in wrapper script by specifying location for log file
                if build_option('debug'):
                    rpath_wrapper_log = os.path.join(tempfile.gettempdir(), 'rpath_wrapper_%s.log' % cmd)
                else:
                    rpath_wrapper_log = '/dev/null'

                # complete template script and put it in place
                cmd_wrapper_txt = read_file(rpath_wrapper_template) % {
                    'orig_cmd': orig_cmd,
                    'python': sys.executable,
                    'rpath_args_py': rpath_args_py,
                    'rpath_filter': rpath_filter,
                    'rpath_include': rpath_include,
                    'rpath_wrapper_log': rpath_wrapper_log,
                    'wrapper_dir': wrapper_dir,
                }
                write_file(cmd_wrapper, cmd_wrapper_txt)
                adjust_permissions(cmd_wrapper, stat.S_IXUSR)

                # prepend location to this wrapper to $PATH
                setvar('PATH', '%s:%s' % (wrapper_dir, os.getenv('PATH')))

                self.log.info("RPATH wrapper script for %s: %s (log: %s)", orig_cmd, which(cmd), rpath_wrapper_log)
            else:
                self.log.debug("Not installing RPATH wrapper for non-existing command '%s'", cmd)

    def handle_sysroot(self):
        """
        Extra stuff to be done when alternate system root is specified via --sysroot EasyBuild configuration option.

        * Update $PKG_CONFIG_PATH to include sysroot location to pkg-config files (*.pc).
        """
        sysroot = build_option('sysroot')
        if sysroot:
            # update $PKG_CONFIG_PATH to include sysroot location to pkg-config files (*.pc)
            sysroot_pc_paths = [os.path.join(sysroot, 'usr', libdir, 'pkgconfig') for libdir in ['lib', 'lib64']]

            pkg_config_path = [p for p in os.getenv('PKG_CONFIG_PATH', '').split(os.pathsep) if p]

            for sysroot_pc_path in sysroot_pc_paths:
                if os.path.exists(sysroot_pc_path):
                    # avoid adding duplicate paths
                    if not any(os.path.exists(x) and os.path.samefile(x, sysroot_pc_path) for x in pkg_config_path):
                        pkg_config_path.append(sysroot_pc_path)

            if pkg_config_path:
                setvar('PKG_CONFIG_PATH', os.pathsep.join(pkg_config_path))

    def _add_dependency_variables(self, names=None, cpp=None, ld=None):
        """ Add LDFLAGS and CPPFLAGS to the self.variables based on the dependencies
            names should be a list of strings containing the name of the dependency
        """
        cpp_paths = ['include']
        ld_paths = ['lib']
        if not self.options.get('32bit', None):
            ld_paths.insert(0, 'lib64')

        if cpp is not None:
            for p in cpp:
                if p not in cpp_paths:
                    cpp_paths.append(p)
        if ld is not None:
            for p in ld:
                if p not in ld_paths:
                    ld_paths.append(p)

        if not names:
            deps = self.dependencies
        else:
            deps = [{'name': name} for name in names if name is not None]

        # collect software install prefixes for dependencies
        roots = []
        for dep in deps:
            if dep.get('external_module', False):
                # for software names provided via external modules, install prefix may be unknown
                names = dep['external_module_metadata'].get('name', [])
                roots.extend([root for root in self.get_software_root(names) if root is not None])
            else:
                roots.extend(self.get_software_root(dep['name']))

        for root in roots:
            self.variables.append_subdirs("CPPFLAGS", root, subdirs=cpp_paths)
            self.variables.append_subdirs("LDFLAGS", root, subdirs=ld_paths)

    def _setenv_variables(self, donotset=None, verbose=True):
        """Actually set the environment variables"""

        self.log.devel("_setenv_variables: setting variables: donotset=%s", donotset)
        if self.dry_run:
            dry_run_msg("Defining build environment...\n", silent=not verbose)

        donotsetlist = []
        if isinstance(donotset, str):
            # TODO : more legacy code that should be using proper type
            raise EasyBuildError("_setenv_variables: using commas-separated list. should be deprecated.")
        elif isinstance(donotset, list):
            donotsetlist = donotset

        for key, val in sorted(self.vars.items()):
            if key in donotsetlist:
                self.log.debug("_setenv_variables: not setting environment variable %s (value: %s).", key, val)
                continue

            self.log.debug("_setenv_variables: setting environment variable %s to %s", key, val)
            setvar(key, val, verbose=verbose)

            # also set unique named variables that can be used in Makefiles
            # - so you can have 'CFLAGS = $(EBVARCFLAGS)'
            # -- 'CLFLAGS = $(CFLAGS)' gives  '*** Recursive variable `CFLAGS'
            # references itself (eventually).  Stop' error
            setvar("EBVAR%s" % key, val, verbose=False)

    def get_flag(self, name):
        """Get compiler flag for a certain option."""
        return "-%s" % self.options.option(name)

    def toolchain_family(self):
        """Return toolchain family for this toolchain."""
        return self.TOOLCHAIN_FAMILY

    def comp_family(self):
        """ Return compiler family used in this toolchain (abstract method)."""
        raise NotImplementedError

    def blas_family(self):
        """Return type of BLAS library used in this toolchain, or 'None' if BLAS is not supported."""
        return None

    def lapack_family(self):
        """Return type of LAPACK library used in this toolchain, or 'None' if LAPACK is not supported."""
        return None

    def mpi_family(self):
        """Return type of MPI library used in this toolchain, or 'None' if MPI is not supported."""
        return None

    def banned_linked_shared_libs(self):
        """
        List of shared libraries (names, file names, paths) which are
        not allowed to be linked in any installed binary/library.
        """
        return []

    def required_linked_shared_libs(self):
        """
        List of shared libraries (names, file names, paths) which
        must be linked in all installed binaries/libraries.
        """
        return []

    def cleanup(self):
        """Clean up after using this toolchain"""
        pass