pw_build: Add pw_cc_binary variant to generate .map files

Bug: b/319746242

Change-Id: I750da45d7cb188d9848f8bd0804367664343da35
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/187710
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ted Pudlik <tpudlik@google.com>
Commit-Queue: Austin Foxley <afoxley@google.com>

6 files changed, 188 insertions, 0 deletions

diff --git a/pw_build/BUILD.bazel b/pw_build/BUILD.bazel
index ed701d706..60adeb7d7 100644
--- a/pw_build/BUILD.bazel
+++ b/pw_build/BUILD.bazel
@@ -14,6 +14,7 @@
 
 load(
     "//pw_build:pigweed.bzl",
+    "pw_cc_binary_with_map",
     "pw_cc_blob_info",
     "pw_cc_blob_library",
     "pw_cc_test",
@@ -59,6 +60,17 @@ pw_cc_test(
     deps = [":test_blob"],
 )
 
+pw_cc_binary_with_map(
+    name = "cc_binary_with_map",
+    srcs = ["empty_main.cc"],
+    # Only enable on platforms that support -Map linker flag
+    target_compatible_with = select({
+        "@platforms//os:macos": ["@platforms//:incompatible"],
+        "@platforms//os:windows": ["@platforms//:incompatible"],
+        "//conditions:default": [],
+    }),
+)
+
 # Bazel produces root-relative file paths without the -ffile-prefix-map option.
 pw_cc_test(
     name = "file_prefix_map_test",
diff --git a/pw_build/BUILD.gn b/pw_build/BUILD.gn
index 4e56015f6..3537c5a26 100644
--- a/pw_build/BUILD.gn
+++ b/pw_build/BUILD.gn
@@ -434,6 +434,11 @@ if (current_toolchain != default_toolchain) {
     visibility = [ ":*" ]
   }
 
+  pw_source_set("empty_main") {
+    sources = [ "empty_main.cc" ]
+    visibility = [ ":*" ]
+  }
+
   pw_test_group("tests") {
     tests = [
       ":cc_blob_library_test",
diff --git a/pw_build/bazel.rst b/pw_build/bazel.rst
index 99c3754dd..a56be9702 100644
--- a/pw_build/bazel.rst
+++ b/pw_build/bazel.rst
@@ -329,6 +329,23 @@ Example
 
    }  // namespace my::stuff
 
+pw_cc_binary_with_map
+---------------------
+The ``pw_cc_binary_with_map`` rule can be used to build a binary like
+``cc_binary`` does but also generate a .map file from the linking step.
+
+.. code-block::
+
+   pw_cc_binary_with_map(
+     name = "test",
+     srcs = ["empty_main.cc"],
+   )
+
+This should result in a ``test.map`` file generated next to the ``test`` binary.
+
+Note that it's only partially compatible with the ``cc_binary`` interface and
+certain things are not implemented like make variable substitution.
+
 Miscellaneous utilities
 -----------------------
 
diff --git a/pw_build/bazel_internal/pigweed_internal.bzl b/pw_build/bazel_internal/pigweed_internal.bzl
index b8b4afb67..be3756c77 100644
--- a/pw_build/bazel_internal/pigweed_internal.bzl
+++ b/pw_build/bazel_internal/pigweed_internal.bzl
@@ -47,6 +47,7 @@ def compile_cc(
         deps,
         includes = [],
         defines = [],
+        local_defines = [],
         user_compile_flags = []):
     """Compiles a list C++ source files.
 
@@ -57,6 +58,7 @@ def compile_cc(
         deps: Dependencies to link with
         includes: List of include paths
         defines: List of preprocessor defines to use
+        local_defines: List of preprocessor defines to use only on this unit.
         user_compile_flags: Extra compiler flags to pass when compiling.
 
     Returns:
@@ -79,6 +81,7 @@ def compile_cc(
         srcs = srcs,
         includes = includes,
         defines = defines,
+        local_defines = local_defines,
         public_hdrs = hdrs,
         user_compile_flags = user_compile_flags,
         compilation_contexts = compilation_contexts,
@@ -104,3 +107,60 @@ def compile_cc(
         compilation_context = compilation_context,
         linking_context = linking_context,
     )]
+
+# From cc_helper.bzl. Feature names for static/dynamic linking.
+linker_mode = struct(
+    LINKING_DYNAMIC = "dynamic_linking_mode",
+    LINKING_STATIC = "static_linking_mode",
+)
+
+def link_cc(
+        ctx,
+        linking_contexts,
+        linkstatic,
+        stamp,
+        user_link_flags = [],
+        additional_outputs = []):
+    """Links a binary and allows custom linker output.
+
+    Args:
+        ctx: Rule context
+        linking_contexts: Dependencies to link with
+        linkstatic: True if binary should be linked statically.
+        stamp: Stamp behavior for linking.
+        user_link_flags: Extra linker flags to pass when linking
+        additional_outputs: Extra files generated by link
+
+    Returns:
+      DefaultInfo of output files
+    """
+    cc_toolchain = find_cpp_toolchain(ctx)
+    features = ctx.features
+    linking_mode = linker_mode.LINKING_STATIC
+    if not linkstatic:
+        linking_mode = linker_mode.LINKING_DYNAMIC
+    features.append(linking_mode)
+    feature_configuration = cc_common.configure_features(
+        ctx = ctx,
+        cc_toolchain = cc_toolchain,
+        requested_features = features,
+        unsupported_features = ctx.disabled_features,
+    )
+
+    linking_outputs = cc_common.link(
+        name = ctx.label.name,
+        actions = ctx.actions,
+        stamp = stamp,
+        feature_configuration = feature_configuration,
+        cc_toolchain = cc_toolchain,
+        linking_contexts = linking_contexts,
+        user_link_flags = user_link_flags,
+        output_type = "executable",
+        additional_outputs = additional_outputs,
+    )
+
+    output_files = depset(
+        [linking_outputs.executable] + additional_outputs,
+        transitive = [],
+    )
+    return [DefaultInfo(files = output_files)]
diff --git a/pw_build/empty_main.cc b/pw_build/empty_main.cc
new file mode 100644
index 000000000..6ef9d5c99
--- /dev/null
+++ b/pw_build/empty_main.cc
@@ -0,0 +1,15 @@
+// Copyright 2024 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+int main() { return 0; }
diff --git a/pw_build/pigweed.bzl b/pw_build/pigweed.bzl
index 13472308b..49b23727a 100644
--- a/pw_build/pigweed.bzl
+++ b/pw_build/pigweed.bzl
@@ -19,6 +19,7 @@ load("@rules_cc//cc:action_names.bzl", "C_COMPILE_ACTION_NAME")
 load(
     "//pw_build/bazel_internal:pigweed_internal.bzl",
     _compile_cc = "compile_cc",
+    _link_cc = "link_cc",
 )
 
 # Used by `pw_cc_test`.
@@ -282,6 +283,84 @@ pw_cc_blob_library = rule(
     toolchains = use_cpp_toolchain(),
 )
 
+def _pw_cc_binary_with_map_impl(ctx):
+    [_, cc_info] = _compile_cc(
+        ctx,
+        ctx.files.srcs,
+        [],
+        deps = ctx.attr.deps + [ctx.attr.link_extra_lib, ctx.attr.malloc],
+        includes = ctx.attr.includes,
+        defines = ctx.attr.defines,
+        local_defines = ctx.attr.local_defines,
+    )
+
+    map_file = ctx.actions.declare_file(ctx.label.name + ".map")
+    map_flags = ["-Wl,-Map=" + map_file.path]
+
+    return _link_cc(
+        ctx,
+        [cc_info.linking_context],
+        ctx.attr.linkstatic,
+        ctx.attr.stamp,
+        user_link_flags = ctx.attr.linkopts + map_flags,
+        additional_outputs = [map_file],
+    )
+
+pw_cc_binary_with_map = rule(
+    implementation = _pw_cc_binary_with_map_impl,
+    doc = """Links a binary like cc_binary does but generates a linker map file
+    and provides it as an output after the executable in the DefaultInfo list
+    returned by this rule.
+
+    This rule makes an effort to somewhat mimic cc_binary args and behavior but
+    doesn't fully support all options currently. Make variable substitution and
+    tokenization handling isn't implemented by this rule on any of it's attrs.
+
+    Args:
+        ctx: Rule context.
+    """,
+    attrs = {
+        "srcs": attr.label_list(
+            allow_files = True,
+            doc = "The list of C and C++ files that are processed to create the target.",
+        ),
+        "deps": attr.label_list(
+            providers = [CcInfo],
+            doc = "The list of other libraries to be linked in to the binary target.",
+        ),
+        "malloc": attr.label(
+            default = "@bazel_tools//tools/cpp:malloc",
+            doc = "Override the default dependency on malloc.",
+        ),
+        "link_extra_lib": attr.label(
+            default = "@bazel_tools//tools/cpp:link_extra_lib",
+            doc = "Control linking of extra libraries.",
+        ),
+        "linkstatic": attr.bool(
+            doc = "True if binary should be link statically",
+        ),
+        "includes": attr.string_list(
+            doc = "List of include dirs to add to the compile line.",
+        ),
+        "defines": attr.string_list(
+            doc = "List of defines to add to the compile line.",
+        ),
+        "local_defines": attr.string_list(
+            doc = "List of defines to add to the compile line.",
+        ),
+        "linkopts": attr.string_list(
+            doc = "Add these flags to the C++ linker command.",
+        ),
+        "stamp": attr.int(
+            default = -1,
+            doc = "Whether to encode build information into the binary.",
+        ),
+    },
+    provides = [DefaultInfo],
+    fragments = ["cpp"],
+    toolchains = use_cpp_toolchain(),
+)
+
 def _preprocess_linker_script_impl(ctx):
     cc_toolchain = find_cpp_toolchain(ctx)
     output_script = ctx.actions.declare_file(ctx.label.name + ".ld")