1# Copyright 2020 The Pigweed Authors
2#
3# Licensed under the Apache License, Version 2.0 (the "License"); you may not
4# use this file except in compliance with the License. You may obtain a copy of
5# the License at
6#
7#     https://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12# License for the specific language governing permissions and limitations under
13# the License.
14
15import("//build_overrides/pigweed.gni")
16
17import("$dir_pw_build/exec.gni")
18import("$dir_pw_build/target_types.gni")
19import("$dir_pw_toolchain/generate_toolchain.gni")
20
21# Preprocess a linker script and turn it into a target.
22#
23# In lieu of direct GN support for linker scripts, this template makes it
24# possible to run the C Preprocessor on a linker script file so defines can
25# be properly evaluated before the linker script is passed to the dir_pw_build
26#
27# TODO(pwbug/53): This template serves as a stand-in until native GN support for
28# linker scripts is added.
29#
30# Args:
31#  linker_script: The linker script to send through the C preprocessor.
32#
33#  defines: Preprocessor defines to apply when running the C preprocessor.
34#
35#  cflags: Flags to pass to the C compiler.
36#
37#  inputs: Files that, when changed, should trigger a re-build of the linker
38#    script. linker_script is implicitly added to this by the template.
39#
40# Example:
41#
42#   pw_linker_script("generic_linker_script") {
43#     defines = [
44#       "PW_HEAP_SIZE=1K",
45#       "PW_NOINIT_SIZE=512"
46#     ]
47#     linker_script = "basic_script.ld"
48#   }
49#
50template("pw_linker_script") {
51  assert(
52      defined(invoker.linker_script) && invoker.linker_script != "",
53      "$target_name did not set `linker_script` to refer to a valid linker " +
54          "script. This variable is required for linker script targets.")
55
56  _final_linker_script = "${target_gen_dir}/${target_name}_final.ld"
57
58  # This action invokes the C compiler provided by the target to preprocess the
59  # linker script.
60  pw_exec("${target_name}_preprocess") {
61    program = pw_toolchain_SCOPE.cxx
62    inputs = [ invoker.linker_script ]
63    args = [
64      # Run compiler in preprocessor-only mode.
65      "-E",
66
67      # Do not generate linemarkers in output.
68      "-P",
69
70      # Do not discard comments.
71      "-C",
72
73      # Treat the following file as a C file.
74      "-x",
75      "c",
76      rebase_path(invoker.linker_script),
77    ]
78
79    # Include any explicitly listed c flags.
80    if (defined(invoker.cflags)) {
81      args += cflags
82    }
83
84    # Add defines.
85    if (defined(invoker.defines)) {
86      foreach(compiler_define, invoker.defines) {
87        args += [ "-D${compiler_define}" ]
88      }
89    }
90
91    # Set output file.
92    args += [
93      "-o",
94      rebase_path(_final_linker_script),
95    ]
96    outputs = [ _final_linker_script ]
97  }
98
99  # This config adds a the linker script produced by the preprocess action to
100  # the linker flags.
101  config("${target_name}_config") {
102    inputs = [ invoker.linker_script ]
103    if (!defined(invoker.ldflags)) {
104      ldflags = []
105    }
106    ldflags += [ "-T" + rebase_path(_final_linker_script) ]
107  }
108
109  # The target that adds the linker script config to this library and everything
110  # that depends on it.
111  pw_source_set(target_name) {
112    inputs = [ _final_linker_script ]
113    if (defined(invoker.inputs)) {
114      inputs += invoker.inputs
115    }
116    all_dependent_configs = [ ":${target_name}_config" ]
117    deps = [ ":${target_name}_preprocess" ]
118  }
119}
120