https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120445
Bug ID: 120445
Summary: False -Wstringop-overread and -Wfree-nonheap-object
positives
Product: gcc
Version: 15.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: christian.morales.vega at gmail dot com
Target Milestone: ---
Using this simple Boost.Json code
```
#include <boost/json/src.hpp>
int main() {
boost::json::value{{"Hello"}};
}
```
results in
```
$ g++ -g -O3 -flto -o /dev/null test.cpp -Iboost_1_88_0
In function 'relocate',
inlined from 'reserve_impl' at
boost_1_88_0/boost/json/impl/array.ipp:692:13,
inlined from 'reserve' at boost_1_88_0/boost/json/impl/array.hpp:474:17,
inlined from 'make_array' at
boost_1_88_0/boost/json/impl/value_ref.ipp:149:16,
inlined from 'make_value' at
boost_1_88_0/boost/json/impl/value_ref.ipp:121:22,
inlined from 'make_value' at
boost_1_88_0/boost/json/impl/value_ref.ipp:95:26:
boost_1_88_0/boost/json/impl/array.hpp:123:17: warning: 'memmove' reading
between 24 and 103079215080 bytes from a region of size 0 [-Wstringop-overread]
123 | std::memmove(
| ^
boost_1_88_0/boost/json/impl/array.ipp: In member function 'make_value':
boost_1_88_0/boost/json/impl/array.ipp:31:14: note: at offset 8 into source
object 'empty_' of size 8
31 | array::table array::empty_;
| ^
In member function 'do_deallocate',
inlined from 'deallocate' at
boost_1_88_0/boost/container/pmr/memory_resource.hpp:54:33,
inlined from 'deallocate' at boost_1_88_0/boost/json/impl/array.ipp:66:19,
inlined from 'reserve_impl' at
boost_1_88_0/boost/json/impl/array.ipp:698:22,
inlined from 'reserve' at boost_1_88_0/boost/json/impl/array.hpp:474:17,
inlined from 'make_array' at
boost_1_88_0/boost/json/impl/value_ref.ipp:149:16,
inlined from 'make_value' at
boost_1_88_0/boost/json/impl/value_ref.ipp:121:22,
inlined from 'make_value' at
boost_1_88_0/boost/json/impl/value_ref.ipp:95:26:
boost_1_88_0/boost/json/detail/impl/default_resource.ipp:53:22: warning:
'operator delete' called on unallocated object 'empty_' [-Wfree-nonheap-object]
53 | ::operator delete(p);
| ^
boost_1_88_0/boost/json/impl/array.ipp: In member function 'make_value':
boost_1_88_0/boost/json/impl/array.ipp:31:14: note: declared here
31 | array::table array::empty_;
| ^
```
AFAICT these are false positives.
-Wstringop-overread complains about the memmove in
https://github.com/boostorg/json/blob/develop/include/boost/json/impl/array.hpp#L123,
but that's never called because just before there is a
```
if(n == 0)
return;
```
and n is certainly 0, since it's initialized to that value in
https://github.com/boostorg/json/blob/develop/include/boost/json/impl/value_ref.ipp#L148.
-Wfree-nonheap-object complains about a delete that, again, is never called
since there is a
```
if(p->capacity == 0)
return;
```
in
https://github.com/boostorg/json/blob/develop/include/boost/json/impl/array.ipp#L64
