2017-07-11  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	* doc/invoke.texi: Document -Wenum-conversion.
	* c-family/c.opt (Wenum-conversion): New option.
	* c/c-typeck.c (convert_for_assignment): Handle Wenum-conversion.

libgomp/
	* icv.c (omp_set_schedule): Cast kind to enum gomp_schedule_type.
	(omp_get_schedule): Cast icv->run_sched_var to enum omp_sched_t
	before.

libgfortran/
	* io/transfer.c (current_mode): Cast FORM_UNSPECIFIED to file_mode.
	(formatted_transfer_scalar_read): Cast SIGN_S, SIGN_SS, SIGN_SP to
	unit_sign.
	(formatted_transfer_scalar_write): Likewise.

testsuite/
	* gcc.dg/Wenum-conversion.c: New test-case.
	* gcc.dg/Wenum-conversion-2.c: Likewise.
	* gcc.dg/Wenum-conversion-3.c: Likewise.

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 05766c47856..6b14203773e 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -500,6 +500,10 @@ Wenum-compare
 C ObjC C++ ObjC++ Var(warn_enum_compare) Init(-1) Warning LangEnabledBy(C ObjC,Wall || Wc++-compat)
 Warn about comparison of different enum types.
 
+Wenum-conversion
+C ObjC Var(warn_enum_conversion) Init(0) Warning LangEnabledBy(C ObjC,Wall)
+Warn about implicit conversion of enum types.
+
 Werror
 C ObjC C++ ObjC++
 ; Documented in common.opt
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 4d067e96dd3..479380f5748 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -6314,6 +6314,32 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 	}
     }
 
+  if (warn_enum_conversion)
+    {
+      tree checktype = origtype != NULL_TREE ? origtype : rhstype;
+      if (checktype != error_mark_node
+	  && TREE_CODE (checktype) == ENUMERAL_TYPE
+	  && TREE_CODE (type) == ENUMERAL_TYPE
+	  && TYPE_MAIN_VARIANT (checktype) != TYPE_MAIN_VARIANT (type))
+	{
+	  tree v1 = TYPE_VALUES (type);
+	  tree v2 = TYPE_VALUES (checktype);
+
+	  /* Do not warn if the enums have same range of values.  */
+	  for (; v1 && v2; v1 = TREE_CHAIN (v1), v2 = TREE_CHAIN (v2))
+	    if (simple_cst_equal (TREE_VALUE (v1), TREE_VALUE (v2)) != 1)
+	      break;
+
+	  if (v1 || v2)
+	    {
+	      gcc_rich_location loc (location);
+	      warning_at_rich_loc (&loc, OPT_Wenum_conversion,
+				   "implicit conversion from %qT to %qT",
+				   checktype, type);
+	    }
+	}
+    }
+
   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (rhstype))
     return rhs;
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f2020f847ae..5fe35515852 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -276,7 +276,8 @@ Objective-C and Objective-C++ Dialects}.
 -Wno-discarded-qualifiers  -Wno-discarded-array-qualifiers @gol
 -Wno-div-by-zero  -Wdouble-promotion @gol
 -Wduplicated-branches  -Wduplicated-cond @gol
--Wempty-body  -Wenum-compare  -Wno-endif-labels  -Wexpansion-to-defined @gol
+-Wempty-body  -Wenum-compare  -Wenum-conversion @gol
+-Wno-endif-labels  -Wexpansion-to-defined @gol
 -Werror  -Werror=*  -Wextra-semi  -Wfatal-errors @gol
 -Wfloat-equal  -Wformat  -Wformat=2 @gol
 -Wno-format-contains-nul  -Wno-format-extra-args  @gol
@@ -3828,6 +3829,7 @@ Options} and @ref{Objective-C and Objective-C++ Dialect Options}.
 -Wcomment  @gol
 -Wduplicate-decl-specifier @r{(C and Objective-C only)} @gol
 -Wenum-compare @r{(in C/ObjC; this is on by default in C++)} @gol
+-Wenum-conversion @r{(in C/ObjC;} @gol
 -Wformat   @gol
 -Wint-in-bool-context  @gol
 -Wimplicit @r{(C and Objective-C only)} @gol
@@ -6074,6 +6076,12 @@ In C++ enumerated type mismatches in conditional expressions are also
 diagnosed and the warning is enabled by default.  In C this warning is 
 enabled by @option{-Wall}.
 
+@item -Wenum-conversion @r{(C, Objective-C only)}
+@opindex Wenum-conversion
+@opindex Wno-enum-conversion
+Warn when an enum value of a type is implicitly converted to an enum valeu of
+another type. This warning is enabled by @option{-Wall}.
+
 @item -Wextra-semi @r{(C++, Objective-C++ only)}
 @opindex Wextra-semi
 @opindex Wno-extra-semi
diff --git a/gcc/testsuite/gcc.dg/Wenum-conversion-2.c b/gcc/testsuite/gcc.dg/Wenum-conversion-2.c
new file mode 100644
index 00000000000..a084ce4fd3c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wenum-conversion-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Wenum-conversion" } */
+
+enum X { x1, x2 };
+enum Y { y1, y2 };
+
+enum X obj = y1;  /* { dg-bogus "implicit conversion from .enum Y. to .enum X." } */
+enum Y obj2 = y1;
+
+enum X obj3;
+void foo()
+{
+  obj3 = y2; /* { dg-bogus "implicit conversion from .enum Y. to .enum X." } */
+}
+
+void bar(enum X);
+void f(void)
+{
+  bar (y1); /* { dg-bogus "implicit conversion from .enum Y. to .enum X." } */
+}
diff --git a/gcc/testsuite/gcc.dg/Wenum-conversion-3.c b/gcc/testsuite/gcc.dg/Wenum-conversion-3.c
new file mode 100644
index 00000000000..9a01bdf2b60
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wenum-conversion-3.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Wenum-conversion" } */
+
+enum X { x1 = 5, x2 };
+enum Y { y1 = 10, y2 };
+
+enum X obj = y1;  /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+enum Y obj2 = y1;
+
+enum X obj3;
+void foo()
+{
+  obj3 = y2; /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+}
+
+void bar(enum X);
+void f(void)
+{
+  bar (y1); /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+}
diff --git a/gcc/testsuite/gcc.dg/Wenum-conversion.c b/gcc/testsuite/gcc.dg/Wenum-conversion.c
new file mode 100644
index 00000000000..177770b4115
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wenum-conversion.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Wenum-conversion" } */
+
+enum X { x1, x2 };
+enum Y { y1, y2, y3 };
+
+enum X obj = y1;  /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+enum Y obj2 = y1;
+
+enum X obj3;
+void foo()
+{
+  obj3 = y2; /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+}
+
+void bar(enum X);
+void f(void)
+{
+  bar (y1); /* { dg-warning "implicit conversion from .enum Y. to .enum X." } */
+}
diff --git a/libgfortran/io/transfer.c b/libgfortran/io/transfer.c
index 298b29e8d3e..ed678895059 100644
--- a/libgfortran/io/transfer.c
+++ b/libgfortran/io/transfer.c
@@ -196,7 +196,7 @@ current_mode (st_parameter_dt *dtp)
 {
   file_mode m;
 
-  m = FORM_UNSPECIFIED;
+  m = (file_mode) FORM_UNSPECIFIED;
 
   if (dtp->u.p.current_unit->flags.access == ACCESS_DIRECT)
     {
@@ -1671,17 +1671,17 @@ formatted_transfer_scalar_read (st_parameter_dt *dtp, bt type, void *p, int kind
 
 	case FMT_S:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_S;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_S;
 	  break;
 
 	case FMT_SS:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_SS;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_SS;
 	  break;
 
 	case FMT_SP:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_SP;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_SP;
 	  break;
 
 	case FMT_BN:
@@ -2130,17 +2130,17 @@ formatted_transfer_scalar_write (st_parameter_dt *dtp, bt type, void *p, int kin
 
 	case FMT_S:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_S;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_S;
 	  break;
 
 	case FMT_SS:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_SS;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_SS;
 	  break;
 
 	case FMT_SP:
 	  consume_data_flag = 0;
-	  dtp->u.p.sign_status = SIGN_SP;
+	  dtp->u.p.sign_status = (unit_sign) SIGN_SP;
 	  break;
 
 	case FMT_BN:
diff --git a/libgomp/icv.c b/libgomp/icv.c
index 233d6dbe10e..71e1f677fd7 100644
--- a/libgomp/icv.c
+++ b/libgomp/icv.c
@@ -87,14 +87,14 @@ omp_set_schedule (omp_sched_t kind, int chunk_size)
     default:
       return;
     }
-  icv->run_sched_var = kind;
+  icv->run_sched_var = (enum gomp_schedule_type) kind;
 }
 
 void
 omp_get_schedule (omp_sched_t *kind, int *chunk_size)
 {
   struct gomp_task_icv *icv = gomp_icv (false);
-  *kind = icv->run_sched_var;
+  *kind = (enum omp_sched_t) icv->run_sched_var;
   *chunk_size = icv->run_sched_chunk_size;
 }