https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98804
Bug ID: 98804
Summary: GCC misparses template in pack expansion as comparison
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: foom at fuhm dot net
CC: richard-gccbugzilla at metafoo dot co.uk
Target Milestone: ---
GCC parses the following program (by Richard Smith) as `g` less-than `a`
greater-than `(a)` instead of a call to the function `g` with template-args
`a`, and argument-list `(a)`. And thus, it fails to compile.
(Compile with -std=c++20)
----
struct X { constexpr X(int&) {} };
template<class F> void g(F);
template<X> void g(int);
void g(...);
template<class ...A> auto h(A ...a)->decltype (g (0, g < a > (a) ...)) {
}
void test () {
h(0);
}
-----
I originally noticed this bug with the following test from Clang's test-suite,
while working on a mangling bug in Clang. In this original test-case, GCC does
successfully compile, but the mangling is weird, exposing that the same
misparse occurred.
----
namespace pr30440 {
template<class F> void g(F);
template<class ...A> auto h(A ...a)->decltype (g (0, g < a > (a) ...)) {
}
void pr30440_test () {
h();
}
}
----
GCC mangles as:
_ZN7pr304401hIJEEEDTcl1gLi0Espgtlt1gfp_fp_EEDpT_
^^^^
with greater/less operators in the mangling.
But it should've been:
_ZN7pr304401hIJEEEDTcl1gLi0Espcl1gIXfp_EEfp_EEEDpT_
^^^^^^^
with a template-arg.
