https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107623
Bug ID: 107623
Summary: Using a parameter pack twice results in ambiguous
overloaded function.
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jlaros at fixedpoint dot nl
Target Milestone: ---
The following example does not compile:
template <class R, class... Args>
void test(R (*)(Args...), Args...) {}
template <class... Args>
void test(void (*)(Args...), Args...) {}
int main() {
void (*f)(int) {};
test(f, 1);
}
Example:
$ g++ -Wall -Wextra -pedantic x.cc
x.cc: In function ‘int main()’:
x.cc:11:7: error: call of overloaded ‘test(void (*&)(int), int)’ is
ambiguous
11 | test(f, 1);
| ~~~~^~~~~~
x.cc:2:6: note: candidate: ‘void test(R (*)(Args ...), Args ...) [with R =
void; Args = {int}]’
2 | void test(R (*)(Args...), Args...) {}
| ^~~~
x.cc:5:6: note: candidate: ‘void test(void (*)(Args ...), Args ...) [with
Args = {int}]’
5 | void test(void (*)(Args...), Args...) {}
| ^~~~
This might be a bug because the following variants on the same theme do compile
without errors or warnings:
template <class R, class T>
void test(R (*)(T), T) {}
template <class T>
void test(void (*)(T), T) {}
And:
template <class R, class... FArgs, class... Args>
void test(R (*)(FArgs...), Args...) {}
template <class... FArgs, class... Args>
void test(void (*)(FArgs...), Args...) {}
The first example does compile when using clang (version 14.0.6).
