Hello!
I'm slowly enabling -Wimplicit-fallthrough on projects in the Mac / iOS ports.
<http://trac.webkit.org/changeset/162793>
<http://clang.llvm.org/docs/LanguageExtensions.html#the-clang-fallthrough-attribute>
This means that if you write any switch statements with implicit fallthroughs
it will produce build errors in projects with the warning enabled.
If you're writing a switch with a fallthrough, use the "FALLTHROUGH;"
annotation (which expands to [[clang::fallthrough]];) to appease the warning.
The intent of this warning is to catch at compile time any accidental switch
fallthroughs, and therefore explicitly annotate everywhere a fallthrough was
intended.
Thanks,
- JoePeck
--
For example. Here is a switch with an implicit fallthrough but no compiler
recognized annotation:
switch (input) {
case 1:
output -= 5;
// fallthrough
default:
output += 5;
}
When the warning is enabled you will see a build error like:
main.cpp:9:5: warning: unannotated fall-through between switch labels
[-Wimplicit-fallthrough]
default:
^
main.cpp:9:5: note: insert 'FALLTHROUGH;' to silence this warning
default:
^
FALLTHROUGH;
main.cpp:9:5: note: insert 'break;' to avoid fall-through
default:
^
break;
Use "FALLTHROUGH;" to annotate the fallthrough and build without errors:
switch (input) {
case 1:
output -= 5;
FALLTHROUGH;
default:
output += 5;
}
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