https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108195
Bug ID: 108195
Summary: Incorrect implicit conversion when assigning
initializer_list to std::vector
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugzilla at al42and dot me
Target Milestone: ---
The following code compiles fine with Clang 15 and GCC 12 and outputs "3" when
run.
With GCC 13, it produces a warning about narrowing conversion and constructs a
vector of length 2.
$ cat test.cpp
#include <iostream>
#include <vector>
struct S
{
S(bool) {}
};
int main()
{
std::vector<S> v = { true, false, true };
std::cout << v.size() << std::endl;
}
$ g++ -std=c++17 test.cpp -o test
test.cpp: In function ‘int main()’:
test.cpp:11:44: warning: narrowing conversion of ‘(((void)const bool [3]{true,
false, true}), ((const bool*)(&<anonymous>)))’ from ‘const bool*’ to ‘bool’
[-Wnarrowing]
11 | std::vector<S> v = { true, false, true };
| ^
test.cpp:11:44: warning: narrowing conversion of ‘(((const
bool*)(&<anonymous>)) + 3)’ from ‘const bool*’ to ‘bool’ [-Wnarrowing]
$ ./test
2
Using a constructor instead of the assignment avoids this problem:
std::vector<S> v { true, false, true }; // works fine
Creating an initializer_list separately is also ok:
std::initializer_list<S> il = { true, false, true };
std::vector<S> v = il; // no problem here, vector has three elements
Tested with GCC fdc7469cf597ec11229ddfc3e9c7a06f3d0fba9d. Bisection points to
d081807d8d70e3e87eae41e1560e54d503f4d465 (PR105838).
