public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c++/66093] New: g++ produces incorrect output on code with constexpr function initializing class with private fields
@ 2015-05-10 19:18 denvned at gmail dot com
0 siblings, 0 replies; only message in thread
From: denvned at gmail dot com @ 2015-05-10 19:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66093
Bug ID: 66093
Summary: g++ produces incorrect output on code with constexpr
function initializing class with private fields
Product: gcc
Version: 5.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: denvned at gmail dot com
Target Milestone: ---
Compiling the following code using command "g++ -std=c++14 main.cpp" produces
an incorrect result:
#include <iostream>
constexpr int n = 10;
struct A {
constexpr operator const int*() const {
return data;
}
constexpr operator int*() {
return data;
}
private:
int data[n];
};
constexpr A f() {
A a{};
for (int i = 1; i <= n; i++) {
a[i] = i;
}
return a;
}
A a = f();
int main()
{
for (int i = 0; i < n; i++) {
std::cout << a[i] << std::endl;
}
}
Expected output of execution of this code is a list of numbers from 1 to 10.
But the program produced by GCC outputs a list of zeroes:
http://coliru.stacked-crooked.com/a/414c82777a938a80
The produced assembly code is clearly incorrect:
https://goo.gl/UJvcOJ
I have found that:
- If "private:" is removed, or
- if "constexpr" is removed from "f()", or
- if "A a = f();" is moved into the body of "main()", or
- if an user defined constructor initializing "data" is added,
then the bug disappears...
Clang produces correct output on this code.
I hope this information will help you fix the bug.
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2015-05-10 19:18 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-05-10 19:18 [Bug c++/66093] New: g++ produces incorrect output on code with constexpr function initializing class with private fields denvned at gmail dot com
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).