From: Jeff Genovy <29107334+jefgen@users.noreply.github.com>
Date: Wed, 12 Sep 2018 17:17:35 +0000 (-0700)
Subject: ICU-13812 Define U_FALLTHROUGH for GCC 7+ for ICU4C. (#100)
X-Git-Tag: release-63-rc~77
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ddf8ff2b7d345ad7b263d904be761670ec1c51a1;p=icu

ICU-13812 Define U_FALLTHROUGH for GCC 7+ for ICU4C. (#100)

Currently U_FALLTHROUGH is not defined for GCC, meaning that any switch case statements with fall-throughs will generate warnings when building ICU4C.

In GCC 7, they added support for: "_attribute_((fallthrough))" which we can now use for U_FALLTHROUGH, which eliminates many warnings when building with GCC.
---

diff --git a/icu4c/source/common/unicode/platform.h b/icu4c/source/common/unicode/platform.h
index db34613b614..4c1603554fb 100644
--- a/icu4c/source/common/unicode/platform.h
+++ b/icu4c/source/common/unicode/platform.h
@@ -517,6 +517,8 @@ namespace std {
             (__has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough"))
 #       define U_FALLTHROUGH [[clang::fallthrough]]
 #   endif
+#elif defined(__GNUC__) && (__GNUC__ >= 7)
+#   define U_FALLTHROUGH __attribute__((fallthrough))
 #endif
 
 #ifndef U_FALLTHROUGH