* c.opt (Wdangling-else): New option.

	* c-parser.c (c_parser_if_statement): Replace OPT_Wparentheses with
	OPT_Wdangling_else.

	* parser.c (cp_parser_selection_statement): Replace OPT_Wparentheses
	with OPT_Wdangling_else.

	* doc/invoke.texi: Document -Wdangling-else.

	* c-c++-common/Wdangling-else-1.c: New test.
	* c-c++-common/Wdangling-else-2.c: New test.
	* c-c++-common/Wdangling-else-3.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@235885 138bc75d-0d04-0410-961f-82ee72b054a4

12 files changed, 116 insertions, 43 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c99daeb457f..17390ab7471 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2016-05-04  Marek Polacek  <polacek@redhat.com>
+
+	* doc/invoke.texi: Document -Wdangling-else.
+
 2016-05-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* config.gcc: Error out when conflicting multilib is detected.  Do not
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 09a72e39e86..e1ba43945c6 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,7 @@
+2016-05-04  Marek Polacek  <polacek@redhat.com>
+
+	* c.opt (Wdangling-else): New option.
+
 2016-05-03  Marek Polacek  <polacek@redhat.com>
 
 	PR c/70859
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 05bfa7cbc6f..bdc6ee0f83b 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -370,6 +370,10 @@ Wctor-dtor-privacy
 C++ ObjC++ Var(warn_ctor_dtor_privacy) Warning
 Warn when all constructors and destructors are private.
 
+Wdangling-else
+C ObjC C++ ObjC++ Var(warn_dangling_else) Warning LangEnabledBy(C ObjC C++ ObjC++,Wparentheses)
+Warn about dangling else.
+
 Wdate-time
 C ObjC C++ ObjC++ CPP(warn_date_time) CppReason(CPP_W_DATE_TIME) Var(cpp_warn_date_time) Init(0) Warning
 Warn about __TIME__, __DATE__ and __TIMESTAMP__ usage.
diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 517a8c6c02e..1e77ef5e40f 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,5 +1,10 @@
 2016-05-04  Marek Polacek  <polacek@redhat.com>
 
+	* c-parser.c (c_parser_if_statement): Replace OPT_Wparentheses with
+	OPT_Wdangling_else.
+
+2016-05-04  Marek Polacek  <polacek@redhat.com>
+
 	PR c/48778
 	* c-typeck.c (build_binary_op): Don't issue -Waddress warnings
 	for macro expansions.
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 701ab45ff89..d275f8ef594 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -5542,7 +5542,7 @@ c_parser_if_statement (c_parser *parser, bool *if_p, vec<tree> *chain)
       /* Diagnose an ambiguous else if if-then-else is nested inside
 	 if-then.  */
       if (nested_if)
-	warning_at (loc, OPT_Wparentheses,
+	warning_at (loc, OPT_Wdangling_else,
 		    "suggest explicit braces to avoid ambiguous %<else%>");
 
       if (warn_duplicated_cond)
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b7375189214..74df11011fc 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2016-05-04  Marek Polacek  <polacek@redhat.com>
+
+	* parser.c (cp_parser_selection_statement): Replace OPT_Wparentheses
+	with OPT_Wdangling_else.
+
 2016-05-03  Martin Sebor  <msebor@redhat.com>
 
 	PR c++/66561
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index c4941a05996..da2ee3cf1dc 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10951,7 +10951,7 @@ cp_parser_selection_statement (cp_parser* parser, bool *if_p,
 		   statement which does have an else clause.  We warn
 		   about the potential ambiguity.  */
 		if (nested_if)
-		  warning_at (EXPR_LOCATION (statement), OPT_Wparentheses,
+		  warning_at (EXPR_LOCATION (statement), OPT_Wdangling_else,
 			      "suggest explicit braces to avoid ambiguous"
 			      " %<else%>");
 		if (warn_duplicated_cond)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 46729db7ac5..96df18e4c31 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -257,7 +257,8 @@ Objective-C and Objective-C++ Dialects}.
 -Wc90-c99-compat -Wc99-c11-compat @gol
 -Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align  -Wcast-qual  @gol
 -Wchar-subscripts -Wclobbered  -Wcomment -Wconditionally-supported  @gol
--Wconversion -Wcoverage-mismatch -Wno-cpp -Wdate-time -Wdelete-incomplete @gol
+-Wconversion -Wcoverage-mismatch -Wno-cpp -Wdangling-else -Wdate-time @gol
+-Wdelete-incomplete @gol
 -Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init @gol
 -Wdisabled-optimization @gol
 -Wno-discarded-qualifiers -Wno-discarded-array-qualifiers @gol
@@ -3976,46 +3977,6 @@ Also warn if a comparison like @code{x<=y<=z} appears; this is
 equivalent to @code{(x<=y ? 1 : 0) <= z}, which is a different
 interpretation from that of ordinary mathematical notation.
 
-Also warn about constructions where there may be confusion to which
-@code{if} statement an @code{else} branch belongs.  Here is an example of
-such a case:
-
-@smallexample
-@group
-@{
-  if (a)
-    if (b)
-      foo ();
-  else
-    bar ();
-@}
-@end group
-@end smallexample
-
-In C/C++, every @code{else} branch belongs to the innermost possible
-@code{if} statement, which in this example is @code{if (b)}.  This is
-often not what the programmer expected, as illustrated in the above
-example by indentation the programmer chose.  When there is the
-potential for this confusion, GCC issues a warning when this flag
-is specified.  To eliminate the warning, add explicit braces around
-the innermost @code{if} statement so there is no way the @code{else}
-can belong to the enclosing @code{if}.  The resulting code
-looks like this:
-
-@smallexample
-@group
-@{
-  if (a)
-    @{
-      if (b)
-        foo ();
-      else
-        bar ();
-    @}
-@}
-@end group
-@end smallexample
-
 Also warn for dangerous uses of the GNU extension to
 @code{?:} with omitted middle operand. When the condition
 in the @code{?}: operator is a boolean expression, the omitted value is
@@ -5148,6 +5109,51 @@ compiler doesn't give this warning for types defined in the main .C
 file, as those are unlikely to have multiple definitions.
 @option{-Wsubobject-linkage} is enabled by default.
 
+@item -Wdangling-else
+@opindex Wdangling-else
+@opindex Wno-dangling-else
+Warn about constructions where there may be confusion to which
+@code{if} statement an @code{else} branch belongs.  Here is an example of
+such a case:
+
+@smallexample
+@group
+@{
+  if (a)
+    if (b)
+      foo ();
+  else
+    bar ();
+@}
+@end group
+@end smallexample
+
+In C/C++, every @code{else} branch belongs to the innermost possible
+@code{if} statement, which in this example is @code{if (b)}.  This is
+often not what the programmer expected, as illustrated in the above
+example by indentation the programmer chose.  When there is the
+potential for this confusion, GCC issues a warning when this flag
+is specified.  To eliminate the warning, add explicit braces around
+the innermost @code{if} statement so there is no way the @code{else}
+can belong to the enclosing @code{if}.  The resulting code
+looks like this:
+
+@smallexample
+@group
+@{
+  if (a)
+    @{
+      if (b)
+        foo ();
+      else
+        bar ();
+    @}
+@}
+@end group
+@end smallexample
+
+This warning is enabled by @option{-Wparentheses}.
+
 @item -Wdate-time
 @opindex Wdate-time
 @opindex Wno-date-time
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 06a1f0766f7..fdf961d72ff 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2016-05-04  Marek Polacek  <polacek@redhat.com>
+
+	* c-c++-common/Wdangling-else-1.c: New test.
+	* c-c++-common/Wdangling-else-2.c: New test.
+	* c-c++-common/Wdangling-else-3.c: New test.
+
 2016-05-04  Kwok Cheung Yeung  <kcy@codesourcery.com>
 
 	* gcc.target/mips/mips16-attributes.c: Skip if -mmicromips
diff --git a/gcc/testsuite/c-c++-common/Wdangling-else-1.c b/gcc/testsuite/c-c++-common/Wdangling-else-1.c
new file mode 100644
index 00000000000..28a5a8f53fb
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wdangling-else-1.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-Wdangling-else" } */
+
+void bar (int);
+void
+foo (int a, int b)
+{
+  if (a) /* { dg-warning "suggest explicit braces to avoid ambiguous" } */
+    if (b)
+      bar (1);
+  else
+    bar (2);
+}
diff --git a/gcc/testsuite/c-c++-common/Wdangling-else-2.c b/gcc/testsuite/c-c++-common/Wdangling-else-2.c
new file mode 100644
index 00000000000..87ea1ab5687
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wdangling-else-2.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-Wparentheses" } */
+
+void bar (int);
+void
+foo (int a, int b)
+{
+  if (a) /* { dg-warning "suggest explicit braces to avoid ambiguous" } */
+    if (b)
+      bar (1);
+  else
+    bar (2);
+}
diff --git a/gcc/testsuite/c-c++-common/Wdangling-else-3.c b/gcc/testsuite/c-c++-common/Wdangling-else-3.c
new file mode 100644
index 00000000000..0dae0d54ec8
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wdangling-else-3.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-Wparentheses -Wno-dangling-else" } */
+
+void bar (int);
+void
+foo (int a, int b)
+{
+  if (a) /* { dg-bogus "suggest explicit braces to avoid ambiguous" } */
+    if (b)
+      bar (1);
+  else
+    bar (2);
+}