gcc/

* common.opt (Wimplicit-fallthrough) Turn into alias to
	-Wimplicit-fallthrough=3.  Remove EnabledBy.
	(Wimplicit-fallthrough=): New option.
	* gimplify.c (warn_implicit_fallthrough_r): Use
	OPT_Wimplicit_fallthrough_ instead of OPT_Wimplicit_fallthrough.
	* doc/invoke.texi (-Wimplicit-fallthrough): Document as alias
	to -Wimplicit-fallthrough=3.
	(-Wimplicit-fallthrough=): Document.
gcc/c-family/
	* c.opt (Wextra): Add as C/C++/ObjC/ObjC++ option.
	(Wimplicit-fallthrough=): Enable for these languages by -Wextra.
	* c-opts.c (sanitize_cpp_opts): Initialize
	cpp_opts->cpp_warn_implicit_fallthrough.
gcc/testsuite/
	* c-c++-common/Wimplicit-fallthrough-25.c: New test.
	* c-c++-common/Wimplicit-fallthrough-26.c: New test.
	* c-c++-common/Wimplicit-fallthrough-27.c: New test.
	* c-c++-common/Wimplicit-fallthrough-28.c: New test.
	* c-c++-common/Wimplicit-fallthrough-29.c: New test.
	* c-c++-common/Wimplicit-fallthrough-30.c: New test.
	* c-c++-common/Wimplicit-fallthrough-31.c: New test.
	* c-c++-common/Wimplicit-fallthrough-32.c: New test.
	* c-c++-common/Wimplicit-fallthrough-33.c: New test.
libcpp/
	* include/cpplib.h (struct cpp_options): Add
	cpp_warn_implicit_fallthrough.
	* init.c (cpp_create_reader): Initialize it to 0.
	* lex.c (fallthrough_comment_p): Handle different
	cpp_warn_implicit_fallthrough levels.  Whitespace fixes.

From-SVN: r241013

gcc/ChangeLog

@@ -1,3 +1,14 @@
+2016-10-12  Jakub Jelinek  <jakub@redhat.com>
+
+	* common.opt (Wimplicit-fallthrough) Turn into alias to
+	-Wimplicit-fallthrough=3.  Remove EnabledBy.
+	(Wimplicit-fallthrough=): New option.
+	* gimplify.c (warn_implicit_fallthrough_r): Use
+	OPT_Wimplicit_fallthrough_ instead of OPT_Wimplicit_fallthrough.
+	* doc/invoke.texi (-Wimplicit-fallthrough): Document as alias
+	to -Wimplicit-fallthrough=3.
+	(-Wimplicit-fallthrough=): Document.
+
 2016-10-11  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* config/sparc/sparc.c (emit_scc_insn): Remove direct support for EQ

gcc/c-family/ChangeLog

@@ -1,3 +1,10 @@
+2016-10-12  Jakub Jelinek  <jakub@redhat.com>
+
+	* c.opt (Wextra): Add as C/C++/ObjC/ObjC++ option.
+	(Wimplicit-fallthrough=): Enable for these languages by -Wextra.
+	* c-opts.c (sanitize_cpp_opts): Initialize
+	cpp_opts->cpp_warn_implicit_fallthrough.
+
 2016-10-11  Marek Polacek  <polacek@redhat.com>
 
 	* c-common.c (warning_candidate_p): Change the return type to bool

gcc/c-family/c-opts.c

@@ -1279,6 +1279,11 @@ sanitize_cpp_opts (void)
   if (flag_working_directory == -1)
     flag_working_directory = (debug_info_level != DINFO_LEVEL_NONE);
 
+  if (warn_implicit_fallthrough < 5)
+    cpp_opts->cpp_warn_implicit_fallthrough = warn_implicit_fallthrough;
+  else
+    cpp_opts->cpp_warn_implicit_fallthrough = 0;
+
   if (cpp_opts->directives_only)
     {
       if (cpp_warn_unused_macros)

gcc/c-family/c.opt

@@ -462,6 +462,10 @@ Werror-implicit-function-declaration
 C ObjC RejectNegative Warning Alias(Werror=, implicit-function-declaration)
 This switch is deprecated; use -Werror=implicit-function-declaration instead.
 
+Wextra
+C ObjC C++ ObjC++ Warning
+; in common.opt
+
 Wfloat-conversion
 C ObjC C++ ObjC++ Var(warn_float_conversion) Warning LangEnabledBy(C ObjC C++ ObjC++,Wconversion)
 Warn for implicit type conversions that cause loss of floating point precision.
@@ -536,6 +540,10 @@ Wimplicit
 C ObjC Var(warn_implicit) Warning LangEnabledBy(C ObjC,Wall)
 Warn about implicit declarations.
 
+Wimplicit-fallthrough=
+LangEnabledBy(C ObjC C++ ObjC++,Wextra,3,0)
+; in common.opt
+
 Wdouble-promotion
 C ObjC C++ ObjC++ Var(warn_double_promotion) Warning
 Warn about implicit conversions from \"float\" to \"double\".

gcc/common.opt

@@ -602,7 +602,10 @@ Common Var(warn_hsa) Init(1) Warning
 Warn when a function cannot be expanded to HSAIL.
 
 Wimplicit-fallthrough
-Common Var(warn_implicit_fallthrough) Warning EnabledBy(Wextra)
+Common Alias(Wimplicit-fallthrough=,3,0) Warning
+
+Wimplicit-fallthrough=
+Common Var(warn_implicit_fallthrough) RejectNegative Joined UInteger Warning
 Warn when a switch case falls through.
 
 Winline

gcc/doc/invoke.texi

@@ -273,8 +273,8 @@ Objective-C and Objective-C++ Dialects}.
 -Wformat-security  -Wformat-signedness  -Wformat-y2k -Wframe-address @gol
 -Wframe-larger-than=@var{len} -Wno-free-nonheap-object -Wjump-misses-init @gol
 -Wignored-qualifiers  -Wignored-attributes  -Wincompatible-pointer-types @gol
--Wimplicit  -Wimplicit-fallthrough  -Wimplicit-function-declaration @gol
--Wimplicit-int @gol
+-Wimplicit  -Wimplicit-fallthrough  -Wimplicit-fallthrough=@var{n} @gol
+-Wimplicit-function-declaration  -Wimplicit-int @gol
 -Winit-self  -Winline  -Wno-int-conversion  -Wint-in-bool-context @gol
 -Wno-int-to-pointer-cast -Winvalid-memory-model -Wno-invalid-offsetof @gol
 -Winvalid-pch -Wlarger-than=@var{len} @gol
@@ -3734,7 +3734,7 @@ name is still supported, but the newer name is more descriptive.)
 @gccoptlist{-Wclobbered  @gol
 -Wempty-body  @gol
 -Wignored-qualifiers @gol
--Wimplicit-fallthrough @gol
+-Wimplicit-fallthrough=3 @gol
 -Wmissing-field-initializers  @gol
 -Wmissing-parameter-type @r{(C only)}  @gol
 -Wold-style-declaration @r{(C only)}  @gol
@@ -4106,6 +4106,12 @@ This warning is enabled by @option{-Wall}.
 @item -Wimplicit-fallthrough
 @opindex Wimplicit-fallthrough
 @opindex Wno-implicit-fallthrough
+@option{-Wimplicit-fallthrough} is the same as @option{-Wimplicit-fallthrough=3}
+and @option{-Wno-implicit-fallthrough} is the same as
+@option{-Wimplicit-fallthrough=0}.
+
+@item -Wimplicit-fallthrough=@var{n}
+@opindex Wimplicit-fallthrough=
 Warn when a switch case falls through.  For example:
 
 @smallexample
@@ -4126,7 +4132,7 @@ switch (cond)
 
 This warning does not warn when the last statement of a case cannot
 fall through, e.g. when there is a return statement or a call to function
-declared with the noreturn attribute.  @option{-Wimplicit-fallthrough}
+declared with the noreturn attribute.  @option{-Wimplicit-fallthrough=}
 also takes into account control flow statements, such as ifs, and only
 warns when appropriate.  E.g.@:
 
@@ -4169,9 +4175,23 @@ switch (cond)
 C++17 provides a standard way to suppress the @option{-Wimplicit-fallthrough}
 warning using @code{[[fallthrough]];} instead of the GNU attribute.  In C++11
 or C++14 users can use @code{[[gnu::fallthrough]];}, which is a GNU extension.
-Instead of the these attributes, it is also possible to add a "falls through"
+Instead of the these attributes, it is also possible to add a fallthrough
 comment to silence the warning.  The whole body of the C or C++ style comment
-should match one of the following regular expressions:
+should match the given regular expressions listed below.  The option argument
+@var{n} specifies what kind of comments are accepted:
+
+@itemize @bullet
+
+@item @option{-Wimplicit-fallthrough=0} disables the warning altogether.
+
+@item @option{-Wimplicit-fallthrough=1} matches @code{.*} regular
+expression, any comment is used as fallthrough comment.
+
+@item @option{-Wimplicit-fallthrough=2} case insensitively matches
+@code{.*falls?[ \t-]*thr(ough|u).*} regular expression.
+
+@item @option{-Wimplicit-fallthrough=3} case sensitively matches one of the
+following regular expressions:
 
 @itemize @bullet
 
@@ -4179,17 +4199,37 @@ should match one of the following regular expressions:
 
 @item @code{@@fallthrough@@}
 
-@item @code{lint -fallthrough ?}
+@item @code{lint -fallthrough[ \t]*}
 
-@item @code{[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?}
+@item @code{[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?@*FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?}
 
-@item @code{[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s | |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?}
+@item @code{[ \t.!]*(Else,? |Intentional(ly)? )?@*Fall((s | |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?}
 
-@item @code{[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s | |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?}
+@item @code{[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?@*fall(s | |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?}
 
 @end itemize
 
-and the comment needs to be followed after optional whitespace and other comments
+@item @option{-Wimplicit-fallthrough=4} case sensitively matches one of the
+following regular expressions:
+
+@itemize @bullet
+
+@item @code{-fallthrough}
+
+@item @code{@@fallthrough@@}
+
+@item @code{lint -fallthrough[ \t]*}
+
+@item @code{[ \t]*FALLTHR(OUGH|U)[ \t]*}
+
+@end itemize
+
+@item @option{-Wimplicit-fallthrough=5} doesn't recognize any comments as
+fallthrough comments, only attributes disable the warning.
+
+@end itemize
+
+The comment needs to be followed after optional whitespace and other comments
 by @code{case} or @code{default} keywords or by a user label that preceeds some
 @code{case} or @code{default} label.
 
@@ -4206,7 +4246,7 @@ switch (cond)
 @end group
 @end smallexample
 
-This warning is enabled by @option{-Wextra}.
+The @option{-Wimplicit-fallthrough=3} warning is enabled by @option{-Wextra}.
 
 @item -Wignored-qualifiers @r{(C and C++ only)}
 @opindex Wignored-qualifiers

gcc/gimplify.c

@@ -1918,7 +1918,7 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
 	    else if (gimple_code (prev) == GIMPLE_LABEL
 		     && (label = gimple_label_label (as_a <glabel *> (prev)))
 		     && (l = find_label_entry (&labels, label)))
-	      warned_p = warning_at (l->loc, OPT_Wimplicit_fallthrough,
+	      warned_p = warning_at (l->loc, OPT_Wimplicit_fallthrough_,
 				     "this statement may fall through");
 	    else if (!gimple_call_internal_p (prev, IFN_FALLTHROUGH)
 		     /* Try to be clever and don't warn when the statement
@@ -1926,7 +1926,7 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
 		     && gimple_stmt_may_fallthru (prev)
 		     && gimple_has_location (prev))
 	      warned_p = warning_at (gimple_location (prev),
-				     OPT_Wimplicit_fallthrough,
+				     OPT_Wimplicit_fallthrough_,
 				     "this statement may fall through");
 	    if (warned_p)
 	      inform (gimple_location (next), "here");

gcc/testsuite/ChangeLog

@@ -1,3 +1,15 @@
+2016-10-12  Jakub Jelinek  <jakub@redhat.com>
+
+	* c-c++-common/Wimplicit-fallthrough-25.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-26.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-27.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-28.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-29.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-30.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-31.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-32.c: New test.
+	* c-c++-common/Wimplicit-fallthrough-33.c: New test.
+
 2016-10-11  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc.target/sparc/setcc-4.c: Adjust.

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-25.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wextra" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-26.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-27.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=1" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-28.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=2" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-29.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=3" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-30.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=4" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-31.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=5" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-warning "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-32.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough=0" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-33.c

@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-Wno-implicit-fallthrough" } */
+
+void bar (int);
+
+void
+foo (int i)
+{
+  switch (i)
+    {
+    case 1:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (1);
+    case 2:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (2);
+      /* Some comment.  */
+    case 3:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (3);
+      /* Here we really do want to fALl   tHRoUgh and we mean it!  */
+    case 4:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (4);
+      /* Intentionally fall through.  */
+    case 5:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (5);
+      /* FALLTHROUGH */
+    case 6:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (6);
+      __attribute__((fallthrough));
+    case 7:			/* { dg-bogus "this statement may \[fla\]* through" "" { target *-*-* } .+1 } */
+      bar (7);
+    default:
+      break;
+    }
+}

libcpp/ChangeLog

@@ -1,3 +1,11 @@
+2016-10-12  Jakub Jelinek  <jakub@redhat.com>
+
+	* include/cpplib.h (struct cpp_options): Add
+	cpp_warn_implicit_fallthrough.
+	* init.c (cpp_create_reader): Initialize it to 0.
+	* lex.c (fallthrough_comment_p): Handle different
+	cpp_warn_implicit_fallthrough levels.  Whitespace fixes.
+
 2016-10-08  Jakub Jelinek  <jakub@redhat.com>
 
 	* lex.c (fallthrough_comment_p): Accept Else, fallthrough.

libcpp/include/cpplib.h

@@ -395,6 +395,9 @@ struct cpp_options
      explicitly undefined.  */
   unsigned char warn_builtin_macro_redefined;
 
+  /* Different -Wimplicit-fallthrough= levels.  */
+  unsigned char cpp_warn_implicit_fallthrough;
+
   /* Nonzero means we should look for header.gcc files that remap file
      names.  */
   unsigned char remap;

libcpp/init.c

@@ -189,6 +189,7 @@ cpp_create_reader (enum c_lang lang, cpp_hash_table *table,
   CPP_OPTION (pfile, warn_dollars) = 1;
   CPP_OPTION (pfile, warn_variadic_macros) = 1;
   CPP_OPTION (pfile, warn_builtin_macro_redefined) = 1;
+  CPP_OPTION (pfile, cpp_warn_implicit_fallthrough) = 0;
   /* By default, track locations of tokens resulting from macro
      expansion.  The '2' means, track the locations with the highest
      accuracy.  Read the comments for struct

libcpp/lex.c

@@ -2040,6 +2040,64 @@ static bool
 fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
 {
   const unsigned char *from = comment_start + 1;
+
+  switch (CPP_OPTION (pfile, cpp_warn_implicit_fallthrough))
+    {
+      /* For both -Wimplicit-fallthrough=0 and -Wimplicit-fallthrough=5 we
+	 don't recognize any comments.  The latter only checks attributes,
+	 the former doesn't warn.  */
+    case 0:
+    default:
+      return false;
+      /* -Wimplicit-fallthrough=1 considers any comment, no matter what
+	 content it has.  */
+    case 1:
+      return true;
+    case 2:
+      /* -Wimplicit-fallthrough=2 looks for (case insensitive)
+	 .*falls?[ \t-]*thr(u|ough).* regex.  */
+      for (; (size_t) (pfile->buffer->cur - from) >= sizeof "fallthru" - 1;
+	   from++)
+	{
+	  /* Is there anything like strpbrk with upper boundary, or
+	     memchr looking for 2 characters rather than just one?  */
+	  if (from[0] != 'f' && from[0] != 'F')
+	    continue;
+	  if (from[1] != 'a' && from[1] != 'A')
+	    continue;
+	  if (from[2] != 'l' && from[2] != 'L')
+	    continue;
+	  if (from[3] != 'l' && from[3] != 'L')
+	    continue;
+	  from += sizeof "fall" - 1;
+	  if (from[0] == 's' || from[0] == 'S')
+	    from++;
+	  while (*from == ' ' || *from == '\t' || *from == '-')
+	    from++;
+	  if (from[0] != 't' && from[0] != 'T')
+	    continue;
+	  if (from[1] != 'h' && from[1] != 'H')
+	    continue;
+	  if (from[2] != 'r' && from[2] != 'R')
+	    continue;
+	  if (from[3] == 'u' || from[3] == 'U')
+	    return true;
+	  if (from[3] != 'o' && from[3] != 'O')
+	    continue;
+	  if (from[4] != 'u' && from[4] != 'U')
+	    continue;
+	  if (from[5] != 'g' && from[5] != 'G')
+	    continue;
+	  if (from[6] != 'h' && from[6] != 'H')
+	    continue;
+	  return true;
+	}
+      return false;
+    case 3:
+    case 4:
+      break;
+    }
+
   /* Whole comment contents:
      -fallthrough
      @fallthrough@
@@ -2060,7 +2118,7 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
       from += 1 + len;
     }
   /* Whole comment contents (regex):
-     lint -fallthrough ?
+     lint -fallthrough[ \t]*
    */
   else if (*from == 'l')
     {
@@ -2068,10 +2126,33 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
       if ((size_t) (pfile->buffer->cur - from - 1) < len)
 	return false;
       if (memcmp (from + 1, "int -fallthrough", len))
-        return false;
+	return false;
       from += 1 + len;
-      if (*from == ' ')
-        from++;
+      while (*from == ' ' || *from == '\t')
+	from++;
+    }
+  /* Whole comment contents (regex):
+     [ \t]*FALLTHR(U|OUGH)[ \t]*
+   */
+  else if (CPP_OPTION (pfile, cpp_warn_implicit_fallthrough) == 4)
+    {
+      while (*from == ' ' || *from == '\t')
+	from++;
+      if ((size_t) (pfile->buffer->cur - from)  < sizeof "FALLTHRU" - 1)
+	return false;
+      if (memcmp (from, "FALLTHR", sizeof "FALLTHR" - 1))
+	return false;
+      from += sizeof "FALLTHR" - 1;
+      if (*from == 'U')
+	from++;
+      else if ((size_t) (pfile->buffer->cur - from)  < sizeof "OUGH" - 1)
+	return false;
+      else if (memcmp (from, "OUGH", sizeof "OUGH" - 1))
+	return false;
+      else
+	from += sizeof "OUGH" - 1;
+      while (*from == ' ' || *from == '\t')
+	from++;
     }
   /* Whole comment contents (regex):
      [ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?
@@ -2085,8 +2166,8 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
       unsigned char f = *from;
       bool all_upper = false;
       if (f == 'E' || f == 'e')
-        {
-          if ((size_t) (pfile->buffer->cur - from)
+	{
+	  if ((size_t) (pfile->buffer->cur - from)
 	      < sizeof "else fallthru" - 1)
 	    return false;
 	  if (f == 'E' && memcmp (from + 1, "LSE", sizeof "LSE" - 1) == 0)
@@ -2096,7 +2177,7 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
 	  from += sizeof "else" - 1;
 	  if (*from == ',')
 	    from++;
-          if (*from != ' ')
+	  if (*from != ' ')
 	    return false;
 	  from++;
 	  if (all_upper && *from == 'f')
@@ -2104,10 +2185,10 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
 	  if (f == 'e' && *from == 'F')
 	    return false;
 	  f = *from;
-        }
+	}
       else if (f == 'I' || f == 'i')
-        {
-          if ((size_t) (pfile->buffer->cur - from)
+	{
+	  if ((size_t) (pfile->buffer->cur - from)
 	      < sizeof "intentional fallthru" - 1)
 	    return false;
 	  if (f == 'I' && memcmp (from + 1, "NTENTIONAL",
@@ -2138,7 +2219,7 @@ fallthrough_comment_p (cpp_reader *pfile, const unsigned char *comment_start)
 	  if (f == 'i' && *from == 'F')
 	    return false;
 	  f = *from;
-        }
+	}
       if (f != 'F' && f != 'f')
 	return false;
       if ((size_t) (pfile->buffer->cur - from) < sizeof "fallthru" - 1)