re PR fortran/54298 (Add warning when doing equal/nonequal floating-point comparisons)

2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>

	PR fortran/54298
	* gfortran.h (struct gfc_option_t): Add warn_compare_reals.
	* lang.opt:  Add Wcompare-reals.
	* invoke.texi:  Document -Wcompare-reals.
	* resolve.c (resolve_operator):  If -Wcompare-reals is in effect,
	warn about equality/inequality comparisions for REAL and COMPLEX.
	* options.c (gfc_init_options):  Set warn_compare_reals.
	(set_Wall):  Include warn_compare_reals in Wall.
	(gfc_handle_option):  Handle Wcompare_reals.

2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>

	PR fortran/54298
	* gfortran.dg/real_compare_1.f90:  New test case.
	* gfortran.dg/bessel_5.f90  Add -Wno-compare-reals to options.

From-SVN: r190516

9 files changed, 83 insertions, 5 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 77e98a0..e91f947c 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,15 @@
+2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>
+
+	PR fortran/54298
+	* gfortran.h (struct gfc_option_t): Add warn_compare_reals.
+	* lang.opt:  Add Wcompare-reals.
+	* invoke.texi:  Document -Wcompare-reals.
+	* resolve.c (resolve_operator):  If -Wcompare-reals is in effect,
+	warn about equality/inequality comparisions for REAL and COMPLEX.
+	* options.c (gfc_init_options):  Set warn_compare_reals.
+	(set_Wall):  Include warn_compare_reals in Wall.
+	(gfc_handle_option):  Handle Wcompare_reals.
+
 2012-08-17  Jakub Jelinek  <jakub@redhat.com>
 
 	* array.c (gfc_match_array_ref): Fix up memset arguments.
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 7c4c0a4..c005151 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -2225,6 +2225,7 @@ typedef struct
   int warn_unused_dummy_argument;
   int warn_realloc_lhs;
   int warn_realloc_lhs_all;
+  int warn_compare_reals;
   int max_errors;
 
   int flag_all_intrinsics;
diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 658ed23..d962ca0 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -726,10 +726,11 @@ warnings.
 @cindex warnings, all
 Enables commonly used warning options pertaining to usage that
 we recommend avoiding and that we believe are easy to avoid.
-This currently includes @option{-Waliasing}, @option{-Wampersand}, 
-@option{-Wconversion}, @option{-Wsurprising}, @option{-Wintrinsics-std},
-@option{-Wno-tabs}, @option{-Wintrinsic-shadow}, @option{-Wline-truncation},
-@option{-Wreal-q-constant} and @option{-Wunused}.
+This currently includes @option{-Waliasing}, @option{-Wampersand},
+@option{-Wconversion}, @option{-Wcompare-reals}, @option{-Wsurprising},
+@option{-Wintrinsics-std}, @option{-Wno-tabs}, @option{-Wintrinsic-shadow},
+@option{-Wline-truncation}, @option{-Wreal-q-constant} and
+@option{-Wunused}.
 
 @item -Waliasing
 @opindex @code{Waliasing}
@@ -935,6 +936,11 @@ a scalar.  See also @option{-frealloc-lhs}.
 Warn when the compiler inserts code to for allocation or reallocation of an
 allocatable variable; this includes scalars and derived types.
 
+@item -Wcompare-reals
+@opindex @code{Wcompare-reals}
+Warn when comparing real or complex types for equality or inequality.
+Enabled by @option{-Wall}.
+
 @item -Werror
 @opindex @code{Werror}
 @cindex warnings, to errors
diff --git a/gcc/fortran/lang.opt b/gcc/fortran/lang.opt
index 3b9d29b..e0c7cf7 100644
--- a/gcc/fortran/lang.opt
+++ b/gcc/fortran/lang.opt
@@ -218,6 +218,10 @@ Wcharacter-truncation
 Fortran Warning
 Warn about truncated character expressions
 
+Wcompare-reals
+Fortran Warning
+Warn about equality comparisons involving REAL or COMPLEX expressions
+
 Wconversion
 Fortran Warning
 ; Documented in C
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index 64d4da1..3e4444d 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -113,6 +113,7 @@ gfc_init_options (unsigned int decoded_options_count,
   gfc_option.warn_unused_dummy_argument = 0;
   gfc_option.warn_realloc_lhs = 0;
   gfc_option.warn_realloc_lhs_all = 0;
+  gfc_option.warn_compare_reals = 0;
   gfc_option.max_errors = 25;
 
   gfc_option.flag_all_intrinsics = 0;
@@ -473,6 +474,7 @@ set_Wall (int setting)
   gfc_option.warn_character_truncation = setting;
   gfc_option.warn_real_q_constant = setting;
   gfc_option.warn_unused_dummy_argument = setting;
+  gfc_option.warn_compare_reals = setting;
 
   warn_return_type = setting;
   warn_switch = setting;
@@ -638,6 +640,10 @@ gfc_handle_option (size_t scode, const char *arg, int value,
       gfc_option.warn_character_truncation = value;
       break;
 
+    case OPT_Wcompare_reals:
+      gfc_option.warn_compare_reals = value;
+      break;
+
     case OPT_Wconversion:
       gfc_option.gfc_warn_conversion = value;
       break;
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index ac5a362..c9be70e0 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -4034,6 +4034,28 @@ resolve_operator (gfc_expr *e)
 
 	  e->ts.type = BT_LOGICAL;
 	  e->ts.kind = gfc_default_logical_kind;
+
+	  if (gfc_option.warn_compare_reals)
+	    {
+	      gfc_intrinsic_op op = e->value.op.op;
+
+	      /* Type conversion has made sure that the types of op1 and op2
+		 agree, so it is only necessary to check the first one.   */
+	      if ((op1->ts.type == BT_REAL || op1->ts.type == BT_COMPLEX)
+		  && (op == INTRINSIC_EQ || op == INTRINSIC_EQ_OS
+		      || op == INTRINSIC_NE || op == INTRINSIC_NE_OS))
+		{
+		  const char *msg;
+
+		  if (op == INTRINSIC_EQ || op == INTRINSIC_EQ_OS)
+		    msg = "Equality comparison for %s at %L";
+		  else
+		    msg = "Inequality comparison for %s at %L";
+		  
+		  gfc_warning (msg, gfc_typename (&op1->ts), &op1->where);
+		}
+	    }
+
 	  break;
 	}
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 378e778..1e29433 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>
+
+	PR fortran/54298
+	* gfortran.dg/real_compare_1.f90:  New test case.
+	* gfortran.dg/bessel_5.f90  Add -Wno-compare-reals to options.
+
 2012-08-18  Jan Hubicka  <jh@suse.cz>
 
 	* gcc.dg/ipa/iinline-1.c: Update testcase to test inline hints.
diff --git a/gcc/testsuite/gfortran.dg/bessel_5.f90 b/gcc/testsuite/gfortran.dg/bessel_5.f90
index aab45ca..0027280 100644
--- a/gcc/testsuite/gfortran.dg/bessel_5.f90
+++ b/gcc/testsuite/gfortran.dg/bessel_5.f90
@@ -1,5 +1,5 @@
 ! { dg-do run }
-! { dg-options "-Wall -fno-range-check" }
+! { dg-options "-Wall -fno-range-check -Wno-compare-reals" }
 !
 ! PR fortran/36158 - Transformational BESSEL_JN/YN
 ! PR fortran/33197 - F2008 math functions
diff --git a/gcc/testsuite/gfortran.dg/real_compare_1.f90 b/gcc/testsuite/gfortran.dg/real_compare_1.f90
new file mode 100644
index 0000000..fd84177
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/real_compare_1.f90
@@ -0,0 +1,21 @@
+! { dg-do compile }
+! { dg-options "-Wcompare-reals" }
+program main
+  real :: a
+  complex :: c
+  read (*,*) a
+  read (*,*) c
+  if (a .eq. 3.14) print *,"foo" ! { dg-warning "Equality comparison for REAL" }
+  if (3.14 == a) print *,"foo" ! { dg-warning "Equality comparison for REAL" }
+  if (a .eq. 3) print *,"foo" ! { dg-warning "Equality comparison for REAL" }
+  if (3. == a) print *,"foo" ! { dg-warning "Equality comparison for REAL" }
+  if (a .ne. 4.14) print *,"foo" ! { dg-warning "Inequality comparison for REAL" }
+  if (4.14 /= a) print *,"foo" ! { dg-warning "Inequality comparison for REAL" }
+  if (a .ne. 4) print *,"foo" ! { dg-warning "Inequality comparison for REAL" }
+  if (4 /= a) print *,"foo" ! { dg-warning "Inequality comparison for REAL" }
+
+  if (c .eq. (3.14, 2.11)) print *,"foo" ! { dg-warning "Equality comparison for COMPLEX" }
+  if ((3.14, 2.11) == a) print *,"foo" ! { dg-warning "Equality comparison for COMPLEX" }
+  if (c .ne. (3.14, 2.11)) print *,"foo" ! { dg-warning "Inequality comparison for COMPLEX" }
+  if ((3.14, 2.11) /= a) print *,"foo" ! { dg-warning "Inequality comparison for COMPLEX" }
+end program main