[PATCH] Fortran: error recovery on arithmetic overflow on unary operations [PR113799]

[PATCH] Fortran: error recovery on arithmetic overflow on unary operations [PR113799]

[Harald Anlauf]

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Dear all,

the attached patch improves error recovery when we encounter an
array constructor where a unary operator (e.g. minus) is applied
and -frange-check is active.  The solution is not to terminate
early in that case to avoid inconsistencies between check_result
and reduce_unary when such a situation occurs.

(There might be similar issues for binary operators, not treated
here.)

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

The ICE/memory corruption is actually a 10+ regression.
Do we need a backport?

Thanks,
Harald


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From eec039211e396e35204b55588013d74289a984cd Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Thu, 8 Feb 2024 21:51:38 +0100
Subject: [PATCH] Fortran: error recovery on arithmetic overflow on unary
 operations [PR113799]

	PR fortran/113799

gcc/fortran/ChangeLog:

	* arith.cc (reduce_unary): Remember any overflow encountered during
	reduction of unary arithmetic operations on array constructors and
	continue, and return error status, but terminate on serious errors.

gcc/testsuite/ChangeLog:

	* gfortran.dg/arithmetic_overflow_2.f90: New test.
---
 gcc/fortran/arith.cc                                | 11 ++++++++---
 gcc/testsuite/gfortran.dg/arithmetic_overflow_2.f90 | 12 ++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/arithmetic_overflow_2.f90

diff --git a/gcc/fortran/arith.cc b/gcc/fortran/arith.cc
index 0598f6ac51b..d17d1aaa1d9 100644
--- a/gcc/fortran/arith.cc
+++ b/gcc/fortran/arith.cc
@@ -1323,6 +1323,7 @@ reduce_unary (arith (*eval) (gfc_expr *, gfc_expr **), gfc_expr *op,
   gfc_constructor *c;
   gfc_expr *r;
   arith rc;
+  bool ov = false;

   if (op->expr_type == EXPR_CONSTANT)
     return eval (op, result);
@@ -1336,13 +1337,17 @@ reduce_unary (arith (*eval) (gfc_expr *, gfc_expr **), gfc_expr *op,
     {
       rc = reduce_unary (eval, c->expr, &r);

-      if (rc != ARITH_OK)
+      /* Remember any overflow encountered during reduction and continue,
+	 but terminate on serious errors.  */
+      if (rc == ARITH_OVERFLOW)
+	ov = true;
+      else if (rc != ARITH_OK)
 	break;

       gfc_replace_expr (c->expr, r);
     }

-  if (rc != ARITH_OK)
+  if (rc != ARITH_OK && rc != ARITH_OVERFLOW)
     gfc_constructor_free (head);
   else
     {
@@ -1363,7 +1368,7 @@ reduce_unary (arith (*eval) (gfc_expr *, gfc_expr **), gfc_expr *op,
       *result = r;
     }

-  return rc;
+  return ov ? ARITH_OVERFLOW : rc;
 }


diff --git a/gcc/testsuite/gfortran.dg/arithmetic_overflow_2.f90 b/gcc/testsuite/gfortran.dg/arithmetic_overflow_2.f90
new file mode 100644
index 00000000000..6ca27f74215
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/arithmetic_overflow_2.f90
@@ -0,0 +1,12 @@
+! { dg-do compile }
+! { dg-additional-options "-frange-check" }
+!
+! PR fortran/113799 - handle arithmetic overflow on unary minus
+
+program p
+  implicit none
+  real, parameter :: inf = real(z'7F800000')
+  real, parameter :: someInf(*) = [inf, 0.]
+  print *, -someInf         ! { dg-error "Arithmetic overflow" }
+  print *, minval(-someInf) ! { dg-error "Arithmetic overflow" }
+end
--
2.35.3

Re: [PATCH] Fortran: error recovery on arithmetic overflow on unary operations [PR113799]

[Jerry D]

On 2/8/24 1:03 PM, Harald Anlauf wrote:
> Dear all,
> 
> the attached patch improves error recovery when we encounter an
> array constructor where a unary operator (e.g. minus) is applied
> and -frange-check is active.  The solution is not to terminate
> early in that case to avoid inconsistencies between check_result
> and reduce_unary when such a situation occurs.
> 
> (There might be similar issues for binary operators, not treated
> here.)
> 
> Regtested on x86_64-pc-linux-gnu.  OK for mainline?
> 
> The ICE/memory corruption is actually a 10+ regression.
> Do we need a backport?
> 
> Thanks,
> Harald
> 

Hi Harald,

This patch looks OK.

Thanks,

Jerry