clang has -Wimplicit-fallthrough and [[clang::fallthrough]]. Lets use them! <http://clang.llvm.org/docs/LanguageExtensions.html#the-clang-fallthrough-attribute> The clang::fallthrough attribute is used along with the -Wimplicit-fallthrough argument to annotate intentional fall-through between switch labels. It can only be applied to a null statement placed at a point of execution between any statement and the next switch label. It is common to mark these places with a specific comment, but this attribute is meant to replace comments with a more strict annotation, which can be checked by the compiler. This attribute doesn’t change semantics of the code and can be used wherever an intended fall-through occurs. It is designed to mimic control-flow statements like break;, so it can be placed in most places where break; can, but only if there are no statements on the execution path between it and the next switch label.
Created attachment 222242 [details] [PATCH] Proposed Fix - FALLTHROUGH Any reason not to add this? This adds it to WTF and enables for WTF. I haven't looked at other projects yet (JSC, WebCore, ...)
Attachment 222242 [details] did not pass style-queue: ERROR: Source/WTF/wtf/Compiler.h:160: Extra space before [ [whitespace/braces] [5] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:235: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:236: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:289: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:290: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:291: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:292: More than one command on the same line [whitespace/newline] [4] Total errors found: 15 in 4 files If any of these errors are false positives, please file a bug against check-webkit-style.
Created attachment 222243 [details] [PATCH] Proposed Fix Now with a ChangeLog.
Attachment 222243 [details] did not pass style-queue: ERROR: Source/WTF/wtf/Compiler.h:160: Extra space before [ [whitespace/braces] [5] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:235: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:236: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:289: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:290: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:291: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:292: More than one command on the same line [whitespace/newline] [4] Total errors found: 15 in 5 files If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 222243 [details] [PATCH] Proposed Fix View in context: https://bugs.webkit.org/attachment.cgi?id=222243&action=review > Source/WTF/wtf/Compiler.h:159 > +#if !defined(FALLTHROUGH) && COMPILER_SUPPORTS(FALLTHROUGH_WARNINGS) > +#if COMPILER(CLANG) Should just be a single #if with another && in it. > Source/WTF/wtf/Compiler.h:165 > +#define FALLTHROUGH do { } while (false) Can this just be defined to nothing? I wouldn’t think it needs to be a statement (see my comments below about semicolons). > Source/WTF/wtf/dtoa/fast-dtoa.cc:257 > + FALLTHROUGH; Does this really require a semicolon after it? That doesn’t seem quite right to me, but maybe that’s how the clang feature works? I don’t think we should keep the "// else fallthrough" comments since we are adding the FALLTHROUGH macros, which say the same thing.
There is an advantage to defining the macro without a semicolon. Clang detects if is a macro with the exact text of the fall through extension. So when it emits a warning it suggests using the macro in the build warning: With: #define FALLTHROUGH [[clang::fallthrough]] CompileC wtf/dtoa/fast-dtoa.cc /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough] case 29: ^ /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: note: insert 'FALLTHROUGH;' to silence this warning case 29: ^ > FALLTHROUGH; /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: note: insert 'break;' to avoid fall-through case 29: ^ break; 1 error generated. However, if the macro is not an exact match, e.g. includes a semicolon, the warning doesn't mention the macro at all: #define FALLTHROUGH [[clang::fallthrough]]; CompileC wtf/dtoa/fast-dtoa.cc /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough] case 29: ^ /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: note: insert '[[clang::fallthrough]];' to silence this warning case 29: ^ > [[clang::fallthrough]]; /Users/pecoraro/Code/webkit/Source/WTF/wtf/dtoa/fast-dtoa.cc:258:13: note: insert 'break;' to avoid fall-through case 29: ^ break; 1 error generated.
Created attachment 222245 [details] [PATCH] For Landing
Attachment 222245 [details] did not pass style-queue: ERROR: Source/WTF/wtf/Compiler.h:159: Extra space before [ [whitespace/braces] [5] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:234: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:235: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:236: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:256: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:257: More than one command on the same line in if [whitespace/parens] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: A case label should not be indented, but line up with its switch statement. [whitespace/indent] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:288: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:289: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:290: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:291: More than one command on the same line [whitespace/newline] [4] ERROR: Source/WTF/wtf/unicode/UTF8.cpp:292: More than one command on the same line [whitespace/newline] [4] Total errors found: 15 in 5 files If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 222245 [details] [PATCH] For Landing Clearing flags on attachment: 222245 Committed r162793: <http://trac.webkit.org/changeset/162793>
All reviewed patches have been landed. Closing bug.