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1# pylint: disable=g-bad-file-header
2# Copyright 2016 The Bazel Authors. All rights reserved.
3#
4# Licensed under the Apache License, Version 2.0 (the "License");
5# you may not use this file except in compliance with the License.
6# You may obtain a copy of the License at
7#
8#    http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS,
12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15
16"""
17Returns the current `CcToolchainInfo`.
18
19* When https://github.com/bazelbuild/bazel/issues/7260 is **not** flipped, current
20  C++ toolchain is selected using the legacy mechanism (`--crosstool_top`,
21  `--cpu`, `--compiler`). For that to work the rule needs to declare an
22  `_cc_toolchain` attribute, e.g.
23
24    foo = rule(
25        implementation = _foo_impl,
26        attrs = {
27            "_cc_toolchain": attr.label(
28                default = Label(
29                    "@rules_cc//cc:current_cc_toolchain", # copybara-use-repo-external-label
30                ),
31            ),
32        },
33    )
34
35* When https://github.com/bazelbuild/bazel/issues/7260 **is** flipped, current
36  C++ toolchain is selected using the toolchain resolution mechanism
37  (`--platforms`). For that to work the rule needs to declare a dependency on
38  C++ toolchain type:
39
40    foo = rule(
41        implementation = _foo_impl,
42        toolchains = [
43            "@rules_cc//cc:toolchain_type", # copybara-use-repo-external-label
44        ],
45    )
46
47We advise to depend on both `_cc_toolchain` attr and on the toolchain type for
48the duration of the migration. After
49https://github.com/bazelbuild/bazel/issues/7260 is flipped (and support for old
50Bazel version is not needed), it's enough to only keep the toolchain type.
51"""
52
53def find_cc_toolchain(ctx):
54    """
55Returns the current `CcToolchainInfo`.
56
57    Args:
58      ctx: The rule context for which to find a toolchain.
59
60    Returns:
61      A CcToolchainInfo.
62    """
63
64    # Check the incompatible flag for toolchain resolution.
65    if hasattr(cc_common, "is_cc_toolchain_resolution_enabled_do_not_use") and cc_common.is_cc_toolchain_resolution_enabled_do_not_use(ctx = ctx):
66        if not "@bazel_tools//tools/cpp:toolchain_type" in ctx.toolchains:
67            fail("In order to use find_cc_toolchain, your rule has to depend on C++ toolchain. See find_cc_toolchain.bzl docs for details.")
68        toolchain_info = ctx.toolchains["@bazel_tools//tools/cpp:toolchain_type"]
69        if hasattr(toolchain_info, "cc_provider_in_toolchain") and hasattr(toolchain_info, "cc"):
70            return toolchain_info.cc
71        return toolchain_info
72
73    # Fall back to the legacy implicit attribute lookup.
74    if hasattr(ctx.attr, "_cc_toolchain"):
75        return ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]
76
77    # We didn't find anything.
78    fail("In order to use find_cc_toolchain, your rule has to depend on C++ toolchain. See find_cc_toolchain.bzl docs for details.")
79
80def find_cpp_toolchain(ctx):
81    """Deprecated, use `find_cc_toolchain` instead.
82
83    Args:
84      ctx: See `find_cc_toolchain`.
85
86    Returns:
87      A CcToolchainInfo.
88    """
89    return find_cc_toolchain(ctx)
90