https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110536
Bug ID: 110536
Summary: Bogus -Wstringop-overflow warning in std::transform
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: eric.niebler at gmail dot com
Target Milestone: ---
Compile the following with -O3 -std=c++17 -Wall
<<<<<<BEGIN
#include <algorithm>
#include <cstdint>
#include <vector>
template <typename TypeParam, typename T>
std::vector<TypeParam>
make_type_param_vector(std::initializer_list<T> const& init_list) {
// std::vector<T> input{init_list}; //uncomment to remove warning
std::vector<TypeParam> vec(init_list.size());
std::transform(std::cbegin(init_list), std::cend(init_list), std::begin(vec),
[](auto const& e) {
if constexpr (std::is_unsigned_v<TypeParam>) { return
static_cast<TypeParam>(std::abs(e)); }
return static_cast<TypeParam>(e);
});
return vec;
}
template <typename T>
void validate_A() {
auto const input_column_valid_a = make_type_param_vector<uint8_t>({1, 0});
auto const input_column_valid_b = make_type_param_vector<uint8_t>({0, 0});
auto const input_column_valid_c = make_type_param_vector<T>({15, 16});
}
int main() {
validate_A<float>();
validate_A<double>();
validate_A<int8_t>();
validate_A<int16_t>();
validate_A<int32_t>();
validate_A<int64_t>();
validate_A<uint8_t>();
validate_A<uint16_t>();
validate_A<uint32_t>();
}
<<<<<<END
Result:
In file included from
/opt/compiler-explorer/gcc-trunk-20230703/include/c++/14.0.0/algorithm:61,
from <source>:1:
In function '_OIter std::transform(_IIter, _IIter, _OIter, _UnaryOperation)
[with _IIter = const int*; _OIter = __gnu_cxx::__normal_iterator<unsigned
char*, vector<unsigned char, allocator<unsigned char> > >; _UnaryOperation =
make_type_param_vector<unsigned char, int>(const
std::initializer_list<int>&)::<lambda(const auto:1&)>]',
inlined from 'std::vector<TypeParam> make_type_param_vector(const
std::initializer_list<T>&) [with TypeParam = unsigned char; T = int]' at
<source>:10:17:
/opt/compiler-explorer/gcc-trunk-20230703/include/c++/14.0.0/bits/stl_algo.h:4216:19:
warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
4216 | *__result = __unary_op(*__first);
| ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
Demo:
https://godbolt.org/z/PKqfjr9cb
