1235717 - (Wunreachable-code) Enable clang's -Wunreachable-code warnings

Status: RESOLVED FIXED

(Firefox Build System :: General, defect)

Description

[Chris Peterson [:cpeterson]]

Attachment: configure_Wunreachable-code.patch

mozilla-central is (almost! :) free of the following clang -Wunreachable-code warnings:

  -Wunreachable-code
  -Wunreachable-code-loop-increment
  -Wunreachable-code-return

Unfortunately, there are still hundreds of -Wunreachable-code-break warnings in the IDL bindings' generated code. clang's meta warning flag -Wunreachable-code-aggressive enables all of the above warnings.

  https://github.com/llvm-mirror/clang/blob/73e51e88d5ed202c6c828d88371f2d694fd9826a/include/clang/Basic/DiagnosticGroups.td#L516

gcc removed support for its -Wunreachable-code warning flag back in 2010 (gcc 4.5) because it produced different results for different -O optimization levels:

  https://gcc.gnu.org/ml/gcc-help/2011-05/msg00362.html

MSVC has an optional warning for unreachable code (C4702), but it is impractical because there are unreachable code warnings in VS2013's own standard library header files.

  https://msdn.microsoft.com/en-us/library/c26da40e.aspx

Here is a green Try build with -Wunreachable-code enabled:

  https://treeherder.mozilla.org/#/jobs?repo=try&revision=7892fcd8ca78

Comment 1

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/c35d01078dad

Comment 2

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/c35d01078dad