https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63203
Bug ID: 63203
Summary: Self-initialization of reference not diagnosed if it
occurs within a loop
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jzwinck at gmail dot com
The following is nonsensical yet compiles cleanly with "g++ -Wall -Wextra
-Werror -Winit-self" (I tested GCC 4.7.2 and 4.9.0):
#include <iostream>
#include <string>
int main()
{
for (int ii = 0; ii < 1; ++ii)
{
const std::string& str = str; // !!
std::cout << str << std::endl;
}
}
The line marked !! results in undefined behavior, yet is not diagnosed by GCC.
However, commenting out the for line makes GCC complain:
error: ‘str’ is used uninitialized in this function [-Werror=uninitialized]
If you change std::string to int and turn on optimization, GCC will diagnose
the error even with the loop.
Ref:
http://stackoverflow.com/questions/25717740/why-is-gcc-tricked-into-allowing-undefined-behavior-simply-by-putting-it-in-a-lo
