Am 22.08.2012 11:18, schrieb Tobias Burnus:
Regarding -Wcompare-real, I wonder whether it makes sense to either
ignore comparisions against zero or to put them into a different flag
(-Wcompare-real-zero);
Here is a patch to not warn for comparisons against zero.
Regression-tested, also tested with make info and make dvi.
OK for trunk?
Thomas
012-08-22 Thomas König <tkoe...@gcc.gnu.org>
PR fortran/54298
* invoke.texi: Document that -Wcompare-reals does not warn for
comparison against zero.
* resolve.c (is_real_zero): New function.
(is_complex_zero): New function.
(resolve_operator): If the comparison is against real or complex
zero, don't warn about equality/inequality comparisions.
Document how to suppress the warning in the error message.
2012-08-22 Thomas König <tkoe...@gcc.gnu.org>
PR fortran/54298
* gfortran.dg/compare_real_2.f90: New test.
Index: invoke.texi
===================================================================
--- invoke.texi (Revision 190541)
+++ invoke.texi (Arbeitskopie)
@@ -939,7 +939,8 @@ allocatable variable; this includes scalars and de
@item -Wcompare-reals
@opindex @code{Wcompare-reals}
Warn when comparing real or complex types for equality or inequality.
-Enabled by @option{-Wall}.
+Comparisons against zero are not warned about. Enabled by
+@option{-Wall}.
@item -Wtarget-lifetime
@opindex @code{Wtargt-lifetime}
Index: resolve.c
===================================================================
--- resolve.c (Revision 190541)
+++ resolve.c (Arbeitskopie)
@@ -3876,7 +3876,27 @@ compare_shapes (gfc_expr *op1, gfc_expr *op2)
return t;
}
+/* Check if an expr is a zero REAL constant. */
+static bool
+is_real_zero (gfc_expr *e)
+{
+ return e->ts.type == BT_REAL && e->expr_type == EXPR_CONSTANT
+ && mpfr_sgn (e->value.real) == 0;
+
+}
+
+/* Check if an expr is a zero COMPLEX constant. */
+
+static bool
+is_complex_zero (gfc_expr *e)
+{
+ return e->ts.type == BT_COMPLEX && e->expr_type == EXPR_CONSTANT
+ && mpfr_sgn (mpc_realref (e->value.complex)) == 0
+ && mpfr_sgn (mpc_imagref (e->value.complex)) == 0;
+
+}
+
/* Resolve an operator expression node. This can involve replacing the
operation with a user defined function call. */
@@ -4047,11 +4067,16 @@ resolve_operator (gfc_expr *e)
{
const char *msg;
+ /* Comparisons against zero are usually legitimate, so let's not warn. */
+ if (is_real_zero (op1) || is_real_zero (op2)
+ || is_complex_zero (op1) || is_complex_zero (op2))
+ break;
+
if (op == INTRINSIC_EQ || op == INTRINSIC_EQ_OS)
- msg = "Equality comparison for %s at %L";
+ msg = "Equality comparison for %s at %L [use -Wno-compare-reals to suppress]";
else
- msg = "Inequality comparison for %s at %L";
-
+ msg = "Inequality comparison for %s at %L [use -Wno-compare-reals to suppress]";
+
gfc_warning (msg, gfc_typename (&op1->ts), &op1->where);
}
}
! { dg-do compile }
! { dg-options "-Wcompare-reals" }
program main
real :: a
complex :: c
read (*,*) a
read (*,*) c
if (a .eq. 0.) print *,"foo"
if (0. == a) print *,"foo"
if (a .eq. 0) print *,"foo"
if (0 == a) print *,"foo"
if (a .ne. 0.0) print *,"foo"
if (0.0 /= a) print *,"foo"
if (a .ne. 0) print *,"foo"
if (0 /= a) print *,"foo"
if (c .eq. (0., 0.)) print *,"foo"
if ((0., 0.) == a) print *,"foo"
if (c .ne. (0., 0.)) print *,"foo"
if ((0., 2.11) /= c) print *,"foo" ! { dg-warning "Inequality comparison for COMPLEX" }
if ((2.11, 0.) /= c) print *,"foo" ! { dg-warning "Inequality comparison for COMPLEX" }
end program main
