Restrict negative offset computation only to dynamic object sizes, where
size expressions are accurate and not a maximum/minimum estimate and in
cases where negative offsets definitely mean an underflow, e.g. in
MEM_REF of the whole object with negative ofset in addr_object_size.
This ends up missing some cases where __builtin_object_size could have
come up with more precise results, so tests have been adjusted to
reflect that.
gcc/ChangeLog:
PR tree-optimization/104009
* tree-object-size.c (compute_builtin_object_size): Bail out on
negative offset.
(plus_stmt_object_size): Return maximum of wholesize and minimum
of 0 for negative offset.
gcc/testsuite/ChangeLog:
PR tree-optimization/104009
* gcc.dg/builtin-object-size-1.c (test10): New test.
* gcc.dg/builtin-object-size-3.c (test10): Likewise.
(test9): Expect zero size for negative offsets.
* gcc.dg/builtin-object-size-4.c (test8): Likewise.
* gcc.dg/builtin-object-size-5.c (test7): Drop test for
__builtin_object_size.
Signed-off-by: Siddhesh Poyarekar <siddh...@gotplt.org>
---
Testing:
- bootstrap build+test for x86_64
- build+test for i686
- bootstrap build --with-build-config=bootstrap-ubsan
gcc/testsuite/gcc.dg/builtin-object-size-1.c | 27 ++++++++++++++++
gcc/testsuite/gcc.dg/builtin-object-size-3.c | 34 +++++++++++++++++---
gcc/testsuite/gcc.dg/builtin-object-size-4.c | 6 ++--
gcc/testsuite/gcc.dg/builtin-object-size-5.c | 2 ++
gcc/tree-object-size.c | 15 +++++++--
5 files changed, 75 insertions(+), 9 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-1.c
b/gcc/testsuite/gcc.dg/builtin-object-size-1.c
index 161f426ec0b..b772e2da9b9 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-1.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-1.c
@@ -603,6 +603,32 @@ test9 (unsigned cond)
#endif
}
+void
+__attribute__ ((noinline))
+test10 (void)
+{
+ static char buf[255];
+ unsigned int i, len = sizeof (buf);
+ char *p = buf;
+
+ for (i = 0 ; i < sizeof (buf) ; i++)
+ {
+ if (len < 2)
+ {
+#ifdef __builtin_object_size
+ if (__builtin_object_size (p - 3, 0) != sizeof (buf) - i + 3)
+ abort ();
+#else
+ if (__builtin_object_size (p - 3, 0) != sizeof (buf))
+ abort ();
+#endif
+ break;
+ }
+ p++;
+ len--;
+ }
+}
+
int
main (void)
{
@@ -617,5 +643,6 @@ main (void)
test7 ();
test8 ();
test9 (1);
+ test10 ();
exit (0);
}
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-3.c
b/gcc/testsuite/gcc.dg/builtin-object-size-3.c
index db31171a8bd..44a99189776 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-3.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-3.c
@@ -581,7 +581,7 @@ test9 (unsigned cond)
if (__builtin_object_size (&p[-4], 2) != (cond ? 6 : 10))
abort ();
#else
- if (__builtin_object_size (&p[-4], 2) != 6)
+ if (__builtin_object_size (&p[-4], 2) != 0)
abort ();
#endif
@@ -592,7 +592,7 @@ test9 (unsigned cond)
if (__builtin_object_size (p, 2) != ((cond ? 2 : 6) + cond))
abort ();
#else
- if (__builtin_object_size (p, 2) != 2)
+ if (__builtin_object_size (p, 2) != 0)
abort ();
#endif
@@ -605,12 +605,37 @@ test9 (unsigned cond)
!= sizeof (y) - __builtin_offsetof (struct A, c) - 8 + cond)
abort ();
#else
- if (__builtin_object_size (p, 2)
- != sizeof (y) - __builtin_offsetof (struct A, c) - 8)
+ if (__builtin_object_size (p, 2) != 0)
abort ();
#endif
}
+void
+__attribute__ ((noinline))
+test10 (void)
+{
+ static char buf[255];
+ unsigned int i, len = sizeof (buf);
+ char *p = buf;
+
+ for (i = 0 ; i < sizeof (buf) ; i++)
+ {
+ if (len < 2)
+ {
+#ifdef __builtin_object_size
+ if (__builtin_object_size (p - 3, 2) != sizeof (buf) - i + 3)
+ abort ();
+#else
+ if (__builtin_object_size (p - 3, 2) != 0)
+ abort ();
+#endif
+ break;
+ }
+ p++;
+ len--;
+ }
+}
+
int
main (void)
{
@@ -625,5 +650,6 @@ main (void)
test7 ();
test8 ();
test9 (1);
+ test10 ();
exit (0);
}
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-4.c
b/gcc/testsuite/gcc.dg/builtin-object-size-4.c
index f644890dd14..b9fddfed036 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-4.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-4.c
@@ -489,7 +489,7 @@ test8 (unsigned cond)
if (__builtin_object_size (&p[-4], 3) != (cond ? 6 : 10))
abort ();
#else
- if (__builtin_object_size (&p[-4], 3) != 6)
+ if (__builtin_object_size (&p[-4], 3) != 0)
abort ();
#endif
@@ -500,7 +500,7 @@ test8 (unsigned cond)
if (__builtin_object_size (p, 3) != ((cond ? 2 : 6) + cond))
abort ();
#else
- if (__builtin_object_size (p, 3) != 2)
+ if (__builtin_object_size (p, 3) != 0)
abort ();
#endif
@@ -512,7 +512,7 @@ test8 (unsigned cond)
if (__builtin_object_size (p, 3) != sizeof (y.c) - 8 + cond)
abort ();
#else
- if (__builtin_object_size (p, 3) != sizeof (y.c) - 8)
+ if (__builtin_object_size (p, 3) != 0)
abort ();
#endif
}
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-5.c
b/gcc/testsuite/gcc.dg/builtin-object-size-5.c
index cb8f753b039..d1ad761cb69 100644
--- a/gcc/testsuite/gcc.dg/builtin-object-size-5.c
+++ b/gcc/testsuite/gcc.dg/builtin-object-size-5.c
@@ -89,6 +89,7 @@ test6 (void)
abort ();
}
+#ifdef __builtin_object_size
void
test7 (void)
{
@@ -97,5 +98,6 @@ test7 (void)
if (__builtin_object_size (p + 2, 0) != 0)
abort ();
}
+#endif
/* { dg-final { scan-assembler-not "abort" } } */
diff --git a/gcc/tree-object-size.c b/gcc/tree-object-size.c
index 3a39e6f15bb..8be0df6ba40 100644
--- a/gcc/tree-object-size.c
+++ b/gcc/tree-object-size.c
@@ -1054,7 +1054,8 @@ compute_builtin_object_size (tree ptr, int
object_size_type,
ptr = gimple_assign_rhs1 (def);
if (((object_size_type & OST_DYNAMIC)
- || tree_fits_shwi_p (offset))
+ || (tree_fits_shwi_p (offset)
+ && compare_tree_int (offset, offset_limit) <= 0))
&& compute_builtin_object_size (ptr, object_size_type,
psize))
{
@@ -1346,8 +1347,18 @@ plus_stmt_object_size (struct object_size_info *osi,
tree var, gimple *stmt)
/* size_for_offset doesn't make sense for -1 size, but it does for size 0
since the wholesize could be non-zero and a negative offset could give
a non-zero size. */
- if (!size_unknown_p (bytes, 0))
+ if (size_unknown_p (bytes, 0))
+ ;
+ else if ((object_size_type & OST_DYNAMIC)
+ || compare_tree_int (op1, offset_limit) <= 0)
bytes = size_for_offset (bytes, op1, wholesize);
+ /* In the static case, with a negative offset, the best estimate for
+ minimum size is size_unknown but for maximum size, the wholesize is a
+ better estimate than size_unknown. */
+ else if (object_size_type & OST_MINIMUM)
+ bytes = size_unknown (object_size_type);
+ else
+ bytes = wholesize;
}
else
bytes = wholesize = size_unknown (object_size_type);
--
2.34.1
