commit 42dd5db90f0cd18e93051e4773df7ae6c636ac23
author Junji Watanabe <jwata@google.com> Mon Feb 03 22:22:42 2025 -0800
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Feb 03 22:22:42 2025 -0800
tree 2b5b23f471af97df348a553e606ec06abde140bf
parent 7132f397c4b29075cbca6d3c215b3a620be9829b

build: Generate gn_logs.txt under build directory for Siso build support

This is necessary to propagate GN variables to Siso.

Bug: 393606976
Change-Id: Iea39d4ca4e55faa8bbaf6a9f4f4c13e57c6a1b4f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/224314
Auto-Submit: Junji Watanabe <jwata@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 7d680b7..197d981 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -113,3 +113,17 @@
   testonly = true
   deps = [ ":all" ]
 }
+
+# GN evaluates each .gn file once per toolchain, so restricting to default
+# toolchain will ensure write_file() is called only once.
+if (current_toolchain == default_toolchain) {
+  import("//build/gn_logs.gni")
+
+  # Write debug logs to gn_logs.txt.
+  _lines = [
+             "Generated during 'gn gen' by //BUILD.gn.",
+             "",
+           ] + build_gn_logs
+
+  write_file("$root_build_dir/gn_logs.txt", _lines)
+}