Flutter engine build failure using clang 10

[JakeSays]

I am re-building my custom engine build using clang 10 and have encountered the following build errors:

In file included from ../../flutter/lib/ui/window/window.cc:5:
In file included from ../../flutter/lib/ui/window/window.h:16:
../../flutter/lib/ui/window/viewport_metrics.h:54:3: error: definition of implicit copy assignment operator for 'ViewportMetrics' is deprecated because it has a user-declared copy constructor [-Werror,-Wdeprecated-copy]
  ViewportMetrics(const ViewportMetrics& other);
  ^
../../flutter/lib/ui/window/window.cc:190:21: note: in implicit copy assignment operator for 'flutter::ViewportMetrics' first required here
  viewport_metrics_ = metrics;

../../third_party/icu/source/i18n/plurrule.cpp:1664:24: error: implicit conversion from 'int64_t' (aka 'long long') to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-int-float-conversion]
          if (scaled > U_INT64_MAX) {
                     ~ ^~~~~~~~~~~
../../third_party/icu/source/common/unicode/umachine.h:212:33: note: expanded from macro 'U_INT64_MAX'
#     define U_INT64_MAX       ((int64_t)(INT64_C(9223372036854775807)))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As an experiment, adding -Wno-deprecated-copy -Wno-implicit-int-float-conversion to toolchain.ninja allowed the build to complete, and the resulting engine runs fine.

Host arch: x86_64 ubuntu linux 19.10
Target arch: arm-linux-gnueabihf

Output of /p/flutter/f/flutter-build-master/flutter/bin/flutter --local-engine=linux_debug_arm --version below (before rebuild):

Flutter 1.12.13+hotfix.8 • channel v1.12.13-hotfixes • https://github.com/flutter/flutter
Framework • revision 0b8abb4724 (9 weeks ago) • 2020-02-11 11:44:36 -0800
Engine • revision e1e6ced81d
Tools • Dart 2.7.0

Note that the exact same source tree built fine with clang 8, same configuration.

[chinmaygarde]

Would you mind preparing an engine patch for this?

[JakeSays]

I can. I'll try to do it this weekend.