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| author | Nathan Sidwell <nathan@acm.org> | 2020-05-04 10:06:40 -0700 |
|---|---|---|
| committer | Nathan Sidwell <nathan@acm.org> | 2020-05-04 10:08:13 -0700 |
| commit | e6b31fc717207565f144aaefa608344789221f07 (patch) | |
| tree | 0e4e6a9f0477e50311c78b9be6c4a1af3a0b2f10 | |
| parent | bb6ce5422066b434f51f6475335788541fd82543 (diff) | |
| download | gcc-e6b31fc717207565f144aaefa608344789221f07.zip gcc-e6b31fc717207565f144aaefa608344789221f07.tar.gz gcc-e6b31fc717207565f144aaefa608344789221f07.tar.bz2 | |
libstdc++: Avoid negating a size_t [pr 94747]
Although the code here is well formed, it doesn't show intent well.
The reason checkers trigger on this is that it is a cause of real
bugs. So, negate a ptrdiff_t instead.
* libsupc++/dyncast.cc (__dynamic_cast): Cast offsetof to
ptrdiff_t before negation, to show intent more clearly.
| -rw-r--r-- | libstdc++-v3/ChangeLog | 6 | ||||
| -rw-r--r-- | libstdc++-v3/libsupc++/dyncast.cc | 11 |
2 files changed, 12 insertions, 5 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 0624bb7..739ab9e 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,9 @@ +2020-05-04 Nathan Sidwell <nathan@acm.org> + + PR libstdc++/94747 + * libsupc++/dyncast.cc (__dynamic_cast): Cast offsetof to + ptrdiff_t before negation, to show intent more clearly. + 2020-05-04 Jonathan Wakely <jwakely@redhat.com> PR libstdc++/94936 diff --git a/libstdc++-v3/libsupc++/dyncast.cc b/libstdc++-v3/libsupc++/dyncast.cc index 1254471..7a5f483 100644 --- a/libstdc++-v3/libsupc++/dyncast.cc +++ b/libstdc++-v3/libsupc++/dyncast.cc @@ -49,8 +49,8 @@ __dynamic_cast (const void *src_ptr, // object started from { const void *vtable = *static_cast <const void *const *> (src_ptr); const vtable_prefix *prefix = - adjust_pointer <vtable_prefix> (vtable, - -offsetof (vtable_prefix, origin)); + (adjust_pointer <vtable_prefix> + (vtable, -ptrdiff_t (offsetof (vtable_prefix, origin)))); const void *whole_ptr = adjust_pointer <void> (src_ptr, prefix->whole_object); const __class_type_info *whole_type = prefix->whole_type; @@ -63,8 +63,8 @@ __dynamic_cast (const void *src_ptr, // object started from // segfault later trying to use a vbase offset that doesn't exist. const void *whole_vtable = *static_cast <const void *const *> (whole_ptr); const vtable_prefix *whole_prefix = - adjust_pointer <vtable_prefix> (whole_vtable, - -offsetof (vtable_prefix, origin)); + (adjust_pointer <vtable_prefix> + (whole_vtable, -ptrdiff_t (offsetof (vtable_prefix, origin)))); if (whole_prefix->whole_type != whole_type) return NULL; @@ -75,7 +75,8 @@ __dynamic_cast (const void *src_ptr, // object started from if (contained_public_p (result.dst2src)) // Src is known to be a public base of dst. return const_cast <void *> (result.dst_ptr); - if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst))) + if (contained_public_p (__class_type_info::__sub_kind + (result.whole2src & result.whole2dst))) // Both src and dst are known to be public bases of whole. Found a valid // cross cast. return const_cast <void *> (result.dst_ptr); |