# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
# vim: set filetype=python:
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.


# Generates a test program and attempts to compile it. In case of failure, the
# resulting check will return None. If the test program succeeds, it will return
# the output of the test program.
# - `includes` are the includes (as file names) that will appear at the top of
#   the generated test program.
# - `body` is the code that will appear in the main function of the generated
#   test program. `return 0;` is appended to the function body automatically.
# - `language` is the language selection, so that the appropriate compiler is
#   used.
# - `flags` are the flags to be passed to the compiler, in addition to `-c`.
# - `check_msg` is the message to be printed to accompany compiling the test
#   program.
@template
def try_compile(includes=None, body='', language='C++', flags=None, check_msg=None,
                when=None, onerror=lambda: None):
    compiler = {
        'C': c_compiler,
        'C++': cxx_compiler,
    }[language]

    return compiler.try_compile(includes, body, flags, check_msg, when=when, onerror=onerror)


# Checks for the presence of the given header on the target system by compiling
# a test program including that header. The return value of the template is a
# check function returning True if the header is present, and None if it is not.
# The value of this check function is also used to set a variable (with set_define)
# corresponding to the checked header. For instance, HAVE_MALLOC_H will be set in
# defines if check_header if called with 'malloc.h' as input and malloc.h is
# present on the target.
# - `header` is the header, as a file name, to check for.
# - `language` is the language selection, so that the appropriate compiler is
#   used.
# - `flags` are the flags to be passed to the compiler, in addition to `-c`.
# - `includes` are additional includes, as file names, to appear before the
#   header checked for.
# - `when` is a depends function that if present will make performing the check
#   conditional on the value of that function.
@template
def check_header(header, language='C++', flags=None, includes=None, when=None):
    if when is None:
        when = always

    if includes:
        includes = includes[:]
    else:
        includes = []
    includes.append(header)

    have_header = try_compile(includes=includes, language=language, flags=flags,
                              check_msg='for %s' % header, when=when)
    header_var = 'HAVE_%s' % (header.upper()
                                    .replace('-', '_')
                                    .replace('/', '_')
                                    .replace('.', '_'))
    set_define(header_var, have_header)
    return have_header

# A convenience wrapper for check_header for checking multiple headers.
# returns an array of the resulting checks in order corresponding to the
# provided headers.
# - `headers` are the headers to be checked.
# - `kwargs` are keyword arguments passed verbatim to check_header.


@template
def check_headers(*headers, **kwargs):
    checks = []
    for header in headers:
        checks.append(check_header(header, **kwargs))
    return checks


# Determine whether to add a given flag to the given lists of flags for C or
# C++ compilation.
# - `flag` is the flag to test
# - `flags_collection` is a @depends function for a namespace of lists of
#    C/C++ compiler flags to add to.
# - `test_flags` is a list of flags to pass to the compiler instead of merely
#   passing `flag`. This is especially useful for checking warning flags. If
#   this list is empty, `flag` will be passed on its own.
# - `compiler` (optional) is the compiler to test against (c_compiler or
#   cxx_compiler, from toolchain.configure). When omitted, both compilers
#   are tested; the list of flags added to is dependent on the compiler tested.
# - `when` (optional) is a @depends function or option name conditioning
#   when the warning flag is wanted.
# - `check`, when not set, skips checking whether the flag is supported and
#   adds it to the list of flags unconditionally.
@template
def check_and_add_flags(flag, flags_collection, test_flags,
                        compiler=None, when=None, check=True):
    if compiler is not None:
        compilers = (compiler,)
    else:
        compilers = (c_compiler, cxx_compiler)

    if when is None:
        when = always

    results = []

    if test_flags:
        flags = test_flags
    else:
        flags = [flag]

    for c in compilers:
        assert c in (c_compiler, cxx_compiler,
                     host_c_compiler, host_cxx_compiler)
        lang, list_of_flags = {
            c_compiler: ('C', flags_collection.cflags),
            cxx_compiler: ('C++', flags_collection.cxxflags),
            host_c_compiler: ('host C', flags_collection.host_cflags),
            host_cxx_compiler: ('host C++', flags_collection.host_cxxflags),
        }[c]

        @depends(c, when)
        def result(c, when):
            if when and c.type in ('clang', 'gcc'):
                return True

        if check:
            result = c.try_compile(
                flags=flags, when=result,
                check_msg='whether the %s compiler supports %s' % (lang, flag))

        @depends(result, list_of_flags)
        def maybe_add_flag(result, list_of_flags):
            if result:
                list_of_flags.append(flag)

        results.append(result)

    return tuple(results)


@dependable
def warnings_flags():
    return namespace(cflags=[], cxxflags=[], host_cflags=[], host_cxxflags=[])


# Tests whether GCC or clang support the given warning flag, and if it is,
# add it to the list of warning flags for the build.
# - `warning` is the warning flag (e.g. -Wfoo)
# - `compiler` (optional) is the compiler to test against (c_compiler or
#   cxx_compiler, from toolchain.configure). When omitted, both compilers
#   are tested.
# - `when` (optional) is a @depends function or option name conditioning
#   when the warning flag is wanted.
# - `check`, when not set, skips checking whether the flag is supported and
#   adds it to the list of warning flags unconditionally. This is only meant
#   for add_gcc_warning().
@template
def check_and_add_gcc_warning(warning, compiler=None, when=None, check=True):
    # GCC and clang will fail if given an unknown warning option like
    # -Wfoobar. But later versions won't fail if given an unknown negated
    # warning option like -Wno-foobar. So when we are checking for support
    # of a negated warning option, we actually test the positive form, but
    # add the negated form to the flags variable.
    if warning.startswith('-Wno-') and not warning.startswith('-Wno-error='):
        flags = ['-Werror', '-W' + warning[5:]]
    elif warning.startswith('-Werror='):
        flags = [warning]
    else:
        flags = ['-Werror', warning]

    return check_and_add_flags(warning, warnings_flags, flags,
                               compiler=compiler, when=when, check=check)


# Add the given warning to the list of warning flags for the build.
# - `warning` is the warning flag (e.g. -Wfoo)
# - `compiler` (optional) is the compiler to add the flag for (c_compiler or
#   cxx_compiler, from toolchain.configure). When omitted, the warning flag
#   is added for both compilers.
# - `when` (optional) is a @depends function or option name conditioning
#   when the warning flag is wanted.


@template
def add_gcc_warning(warning, compiler=None, when=None):
    check_and_add_gcc_warning(warning, compiler, when, check=False)


# Like the warning checks above, but for general compilation flags.
@dependable
def compilation_flags():
    return namespace(cflags=[], cxxflags=[], host_cflags=[], host_cxxflags=[])


# Tests whether GCC or clang support the given compilation flag; if the flag
# is supported, add it to the list of compilation flags for the build.
# - `flag` is the flag to test
# - `compiler` (optional) is the compiler to test against (c_compiler or
#   cxx_compiler, from toolchain.configure). When omitted, both compilers
#   are tested.
# - `when` (optional) is a @depends function or option name conditioning
#   when the warning flag is wanted.
# - `check`, when not set, skips checking whether the flag is supported and
#   adds it to the list of flags unconditionally. This is only meant for
#   add_gcc_flag().
@template
def check_and_add_gcc_flag(flag, compiler=None, when=None, check=True):
    flags = ['-Werror', flag]

    return check_and_add_flags(flag, compilation_flags, flags,
                               compiler=compiler, when=when, check=check)


# Add the given flag to the list of flags for the build.
# - `flag` is the flag (e.g. -fno-sized-deallocation)
# - `compiler` (optional) is the compiler to add the flag for (c_compiler or
#   cxx_compiler, from toolchain.configure). When omitted, the flag is added
#   for both compilers.
# - `when` (optional) is a @depends function or option name conditioning
#   when the flag is wanted.
@template
def add_gcc_flag(warning, compiler=None, when=None):
    check_and_add_gcc_flag(warning, compiler, when, check=False)