sanitizer: missing signed integer overflow errors [PR109107]

Here we're failing to detect a signed overflow with -O because match.pd,
since r8-1516, transforms

  c = (a + 1) - (int) (short int) b;

into

  c = (int) ((unsigned int) a + 4294946117);

wrongly eliding the overflow.  This kind of problems is usually
avoided by using TYPE_OVERFLOW_SANITIZED in the appropriate place.
The first match.pd hunk in the patch fixes it.  I've constructed
a testcase for each of the surrounding cases as well.  Then I
noticed that fold_binary_loc/associate has the same problem, so I've
added a TYPE_OVERFLOW_SANITIZED there as well (it may be too coarse,
sorry).  Then I found yet another problem, but instead of fixing it
now I've opened 109134.  I could probably go on and find a dozen more.

	PR sanitizer/109107

gcc/ChangeLog:

	* fold-const.cc (fold_binary_loc): Use TYPE_OVERFLOW_SANITIZED
	when associating.
	* match.pd: Use TYPE_OVERFLOW_SANITIZED.

gcc/testsuite/ChangeLog:

	* c-c++-common/ubsan/pr109107-1.c: New test.
	* c-c++-common/ubsan/pr109107-2.c: New test.
	* c-c++-common/ubsan/pr109107-3.c: New test.
	* c-c++-common/ubsan/pr109107-4.c: New test.

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 5b9982e36511ca1678e90f4c91525fae9a84c91e..3b397ae2941dc2f714831f2b162eca59f855d64a 100644 (file)
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -11320,7 +11320,8 @@ fold_binary_loc (location_t loc, enum tree_code code, tree type,
         And, we need to make sure type is not saturating.  */
 
       if ((! FLOAT_TYPE_P (type) || flag_associative_math)
-         && !TYPE_SATURATING (type))
+         && !TYPE_SATURATING (type)
+         && !TYPE_OVERFLOW_SANITIZED (type))
        {
          tree var0, minus_var0, con0, minus_con0, lit0, minus_lit0;
          tree var1, minus_var1, con1, minus_con1, lit1, minus_lit1;

diff --git a/gcc/match.pd b/gcc/match.pd
index b8d3538b80947dfc46d0f90d246317d64a4ace5d..c5d2c36e117298782bc154eaed1b381bf3418701 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2933,7 +2933,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        /* If the constant operation overflows we cannot do the transform
          directly as we would introduce undefined overflow, for example
          with (a - 1) + INT_MIN.  */
-       (if (types_match (type, @0))
+       (if (types_match (type, @0) && !TYPE_OVERFLOW_SANITIZED (type))
        (with { tree cst = const_binop (outer_op == inner_op
                                        ? PLUS_EXPR : MINUS_EXPR,
                                        type, @1, @2); }
@@ -2964,7 +2964,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
      (if (!ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
          || TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
       (view_convert (minus (outer_op @1 (view_convert @2)) @0))
-      (if (types_match (type, @0))
+      (if (types_match (type, @0) && !TYPE_OVERFLOW_SANITIZED (type))
        (with { tree cst = const_binop (outer_op, type, @1, @2); }
        (if (cst && !TREE_OVERFLOW (cst))
         (minus { cst; } @0))))))))
@@ -2983,7 +2983,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
     (if (!ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
         || TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
      (view_convert (plus @0 (minus (view_convert @1) @2)))
-     (if (types_match (type, @0))
+     (if (types_match (type, @0) && !TYPE_OVERFLOW_SANITIZED (type))
       (with { tree cst = const_binop (MINUS_EXPR, type, @1, @2); }
        (if (cst && !TREE_OVERFLOW (cst))
        (plus { cst; } @0)))))))

diff --git a/gcc/testsuite/c-c++-common/ubsan/pr109107-1.c b/gcc/testsuite/c-c++-common/ubsan/pr109107-1.c
new file mode 100644 (file)
index 0000000..ca4dd0e
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/ubsan/pr109107-1.c
@@ -0,0 +1,23 @@
+/* PR sanitizer/109107 */
+/* { dg-do run { target int32 } } */
+/* { dg-options "-fsanitize=signed-integer-overflow" } */
+
+#define INT_MIN (-__INT_MAX__ - 1)
+int a = INT_MIN;
+const int b = 676540;
+
+__attribute__((noipa)) int
+foo ()
+{
+  int c = a + 1 - (int) (short) b;
+  return c;
+}
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}
+
+/* { dg-output "signed integer overflow: -2147483647 - 21180 cannot be represented in type 'int'" } */

diff --git a/gcc/testsuite/c-c++-common/ubsan/pr109107-2.c b/gcc/testsuite/c-c++-common/ubsan/pr109107-2.c
new file mode 100644 (file)
index 0000000..eb440b5
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/ubsan/pr109107-2.c
@@ -0,0 +1,24 @@
+/* PR sanitizer/109107 */
+/* { dg-do run { target int32 } } */
+/* { dg-options "-fsanitize=signed-integer-overflow" } */
+
+#define INT_MIN (-__INT_MAX__ - 1)
+int a = INT_MIN;
+const int b = 676540;
+
+__attribute__((noipa)) int
+foo ()
+{
+  int c = a - 1 + (int) (short) b;
+  return c;
+}
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}
+
+/* { dg-output "signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*signed integer overflow: 2147483647 \\+ 21180 cannot be represented in type 'int'" } */

diff --git a/gcc/testsuite/c-c++-common/ubsan/pr109107-3.c b/gcc/testsuite/c-c++-common/ubsan/pr109107-3.c
new file mode 100644 (file)
index 0000000..fa074e7
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/ubsan/pr109107-3.c
@@ -0,0 +1,25 @@
+/* PR sanitizer/109107 */
+/* { dg-do run { target int32 } } */
+/* { dg-options "-fsanitize=signed-integer-overflow" } */
+
+#define INT_MIN (-__INT_MAX__ - 1)
+const int a = INT_MIN;
+const int b = 40;
+int d = 1;
+
+__attribute__((noipa)) int
+foo ()
+{
+  int c = a - d + (int) (short) b;
+  return c;
+}
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}
+
+/* { dg-output "signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*signed integer overflow: 2147483647 \\+ 40 cannot be represented in type 'int'" } */

diff --git a/gcc/testsuite/c-c++-common/ubsan/pr109107-4.c b/gcc/testsuite/c-c++-common/ubsan/pr109107-4.c
new file mode 100644 (file)
index 0000000..b0ac987
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/ubsan/pr109107-4.c
@@ -0,0 +1,24 @@
+/* PR sanitizer/109107 */
+/* { dg-do run { target int32 } } */
+/* { dg-options "-fsanitize=signed-integer-overflow" } */
+
+#define INT_MIN (-__INT_MAX__ - 1)
+const int x = INT_MIN;
+const int y = -2;
+int a = -3;
+
+__attribute__((noipa)) int
+foo ()
+{
+  int c = x - (y - a);
+  return c;
+}
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}
+
+/* { dg-output "signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'" } */