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| author | Marek Polacek <polacek@redhat.com> | 2020-11-03 15:10:31 -0500 |
|---|---|---|
| committer | Marek Polacek <polacek@redhat.com> | 2020-11-05 16:34:22 -0500 |
| commit | e6fd02cc6d874c523466250a1cb724e0c7af9d75 (patch) | |
| tree | 34151764b20973ce61fe02249b2ba515b3cfe2b2 /gcc | |
| parent | 1d87302a8e20c1f49dd37177ec869ee94abc11a5 (diff) | |
| download | gcc-e6fd02cc6d874c523466250a1cb724e0c7af9d75.zip gcc-e6fd02cc6d874c523466250a1cb724e0c7af9d75.tar.gz gcc-e6fd02cc6d874c523466250a1cb724e0c7af9d75.tar.bz2 | |
c++: Fix decltype(auto) deduction with rvalue ref [PR78209]
Here's a small deficiency in decltype(auto). [dcl.type.auto.deduct]/5:
If the placeholder-type-specifier is of the form decltype(auto), [...]
the type deduced for T is determined [...] as though E had been the operand
of the decltype. So:
int &&i = 0;
decltype(auto) j = i; // should behave like int &&j = i; error
We deduce j's type in do_auto_deduction via finish_decltype_type which
takes an 'id' argument. Currently we compute 'id' as false, because
stripped_init is *i (a REFERENCE_REF_P). But it seems to me we should
rather set 'id' to true here, by looking through the REFERENCE_REF_P,
so that finish_decltype_type DTRT.
gcc/cp/ChangeLog:
PR c++/78209
* pt.c (do_auto_deduction): If init is REFERENCE_REF_P, use its
first operand.
gcc/testsuite/ChangeLog:
PR c++/78209
* g++.dg/cpp1y/decltype-auto1.C: New test.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/cp/pt.c | 2 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp1y/decltype-auto1.C | 8 |
2 files changed, 10 insertions, 0 deletions
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index f401c75..c033a28 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -29278,6 +29278,8 @@ do_auto_deduction (tree type, tree init, tree auto_node, else if (AUTO_IS_DECLTYPE (auto_node)) { tree stripped_init = tree_strip_any_location_wrapper (init); + if (REFERENCE_REF_P (stripped_init)) + stripped_init = TREE_OPERAND (stripped_init, 0); bool id = (DECL_P (stripped_init) || ((TREE_CODE (init) == COMPONENT_REF || TREE_CODE (init) == SCOPE_REF) diff --git a/gcc/testsuite/g++.dg/cpp1y/decltype-auto1.C b/gcc/testsuite/g++.dg/cpp1y/decltype-auto1.C new file mode 100644 index 0000000..13baf8e --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/decltype-auto1.C @@ -0,0 +1,8 @@ +// PR c++/78209 +// { dg-do compile { target c++14 } } + +int main() +{ + int &&i = 0; + decltype(auto) j = i; // { dg-error "cannot bind rvalue reference" } +} |