https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66197
Bug ID: 66197
Summary: c++1z generic function wrong type for auto
Product: gcc
Version: 5.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: theonetruekenny at yahoo dot com
Target Milestone: ---
https://gcc.gnu.org/ml/gcc-help/2015-05/msg00066.html
#include <iostream>
auto add_1(auto a, auto b) { return a + b;}
auto add_2 = [](auto a, auto b) { return a + b;};
int main()
{
std::cout
<< "a1: " << add_1(3.5, 4) << "\n"
<< "a2: " << add_1(3, 4.5) << "\n"
<< "a3: " << add_2(3.5, 4) << "\n"
<< "a4: " << add_2(3, 4.5) << "\n";
}
This gives me:
a1: 7.5
a2: 7
a3: 7.5
a4: 7.5
But the expected value for a2 would also be 7.5.
This was with This is with a fedora 22/x86-64 machine.
gcc version 5.1.1 20150422 (Red Hat 5.1.1-1) (GCC)
According to the current spec:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3889.pdf
15 "A generic function is denoted by function declarator having auto
or a concept-name as part of the type-specifier in its
parameter-declaration-clause"
17 "All placeholder types introduced using the same concept-name have
the same invented template parameter."
It would appear that gcc is applying the rule from 17 even in the case of
'auto'.
