re PR fortran/44055 (Warn (-Wconversion*) when converting single to double precision)

gcc/fortran/:
2010-05-19  Daniel Franke  <franke.daniel@gmail.com>

	PR fortran/44055
	* lang.opt (Wconversion-extra): New option.
	* gfortran.h (gfc_option_t): Add warn_conversion_extra.
	* options.c (gfc_init_options): Disable -Wconversion-extra by default.
	(set_Wall): Enable -Wconversion.
	(gfc_handle_option): Set warn_conversion_extra.
	* intrinsic.c (gfc_convert_type_warn): Ignore kind conditions
	introduced for -Wconversion if -Wconversion-extra is present.
	* invoke.texi: Add -Wconversion to -Wall; document new behaviour of
	-Wconversion; document -Wconversion-extra.

gcc/testsuite/:
2010-05-19  Daniel Franke  <franke.daniel@gmail.com>

	PR fortran/44055
	* gfortran.dg/c_sizeof_2.f90: Add -Wno-conversion to dg-options;
	Fixed scope of C_SIZEOF.
	* gfortran.dg/warn_conversion_2.f90: New.

From-SVN: r159586

1 files changed, 35 insertions, 12 deletions

diff --git a/gcc/fortran/intrinsic.c b/gcc/fortran/intrinsic.c
index 02dea30..a92b5b5 100644
--- a/gcc/fortran/intrinsic.c
+++ b/gcc/fortran/intrinsic.c
@@ -4015,18 +4015,38 @@ gfc_convert_type_warn (gfc_expr *expr, gfc_typespec *ts, int eflag, int wflag)
 
   /* At this point, a conversion is necessary. A warning may be needed.  */
   if ((gfc_option.warn_std & sym->standard) != 0)
-    gfc_warning_now ("Extension: Conversion from %s to %s at %L",
-		     gfc_typename (&from_ts), gfc_typename (ts), &expr->where);
-  else if (wflag && gfc_option.warn_conversion)
     {
+      gfc_warning_now ("Extension: Conversion from %s to %s at %L",
+		       gfc_typename (&from_ts), gfc_typename (ts),
+		       &expr->where);
+    }
+  else if (wflag)
+    {
+      /* Two modes of warning:
+	  - gfc_option.warn_conversion tries to be more intelligent
+	    about the warnings raised and omits those where smaller
+	    kinds are promoted to larger ones without change in the
+	    value
+	  - gfc_option.warn_conversion_extra does not take the kinds
+	    into account and also warns for coversions like
+	    REAL(4) -> REAL(8)
+
+	 NOTE: Possible enhancement for warn_conversion
+	 If converting from a smaller to a larger kind, check if the
+	 value is constant and if yes, whether the value still fits
+	 in the smaller kind. If yes, omit the warning.
+      */
+
       /* If the types are the same (but not LOGICAL), and if from-kind
 	 is larger than to-kind, this may indicate a loss of precision.
 	 The same holds for conversions from REAL to COMPLEX.  */
       if (((from_ts.type == ts->type && from_ts.type != BT_LOGICAL)
-	     && from_ts.kind > ts->kind)
+           && ((gfc_option.warn_conversion && from_ts.kind > ts->kind)
+	       || gfc_option.warn_conversion_extra))
 	  || ((from_ts.type == BT_REAL && ts->type == BT_COMPLEX)
-	      && from_ts.kind > ts->kind))
-	gfc_warning_now ("Possible loss of precision in conversion "
+	      && ((gfc_option.warn_conversion && from_ts.kind > ts->kind)
+		  || gfc_option.warn_conversion_extra)))
+	gfc_warning_now ("Possible change of value in conversion "
 			 "from %s to %s at %L", gfc_typename (&from_ts),
 			 gfc_typename (ts), &expr->where);
 
@@ -4037,18 +4057,21 @@ gfc_convert_type_warn (gfc_expr *expr, gfc_typespec *ts, int eflag, int wflag)
 	 an overflow error with range checking. */
       else if (from_ts.type == BT_INTEGER
 	       && (ts->type == BT_REAL || ts->type == BT_COMPLEX)
-	       && from_ts.kind > ts->kind)
-	gfc_warning_now ("Possible loss of digits in conversion "
+	       && ((gfc_option.warn_conversion && from_ts.kind > ts->kind)
+		   || gfc_option.warn_conversion_extra))
+	gfc_warning_now ("Possible change of value in conversion "
 			 "from %s to %s at %L", gfc_typename (&from_ts),
 			 gfc_typename (ts), &expr->where);
 
       /* If REAL/COMPLEX is converted to INTEGER, or COMPLEX is converted
         to REAL we almost certainly have a loss of digits, regardless of
         the respective kinds.  */
-      else if (((from_ts.type == BT_REAL || from_ts.type == BT_COMPLEX)
-		 && ts->type == BT_INTEGER)
-	       || (from_ts.type == BT_COMPLEX && ts->type == BT_REAL))
-	gfc_warning_now ("Likely loss of digits in conversion from"
+      else if ((((from_ts.type == BT_REAL || from_ts.type == BT_COMPLEX)
+		  && ts->type == BT_INTEGER)
+		|| (from_ts.type == BT_COMPLEX && ts->type == BT_REAL))
+	       && (gfc_option.warn_conversion
+	           || gfc_option.warn_conversion_extra))
+	gfc_warning_now ("Possible change of value in conversion from "
 			"%s to %s at %L", gfc_typename (&from_ts),
 			gfc_typename (ts), &expr->where);
     }