diff options
| author | Jason Merrill <jason@redhat.com> | 2020-05-25 18:38:09 -0400 |
|---|---|---|
| committer | Jason Merrill <jason@redhat.com> | 2020-05-25 18:38:11 -0400 |
| commit | 0296697cf9893dc9509cdcd8e3fd4ba9fe422527 (patch) | |
| tree | 4afde3d10d63d3fb30cc3d87c129bc995c99a447 | |
| parent | e153e0ef3a35c2c72e8bf89bd905fe27f8877852 (diff) | |
c++: constexpr and lambda capture [PR90212]
This is the same issue as PR86429, just in potential_constant_expression_1
rather than cxx_eval_constant_expression. As in that case, when we're
trying to evaluate a constant expression within a lambda, we don't have a
constant closure object to refer to, but we can try to refer directly to the
captured variable.
gcc/cp/ChangeLog
2020-05-05 Jason Merrill <jason@redhat.com>
PR c++/90212
* constexpr.c (potential_constant_expression_1): In a lambda
function, consider a captured variable directly.
| -rw-r--r-- | gcc/cp/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/cp/constexpr.c | 8 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp0x/lambda/lambda-constexpr2.C | 13 |
3 files changed, 26 insertions, 1 deletions
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 7626511b9ca..87fb9c0147a 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,5 +1,11 @@ 2020-05-25 Jason Merrill <jason@redhat.com> + PR c++/90212 + * constexpr.c (potential_constant_expression_1): In a lambda + function, consider a captured variable directly. + +2020-05-25 Jason Merrill <jason@redhat.com> + PR c++/90479 * init.c (get_nsdmi): Don't push_to_top_level for a local class. diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index b349919b434..3465f1db54b 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -6159,12 +6159,18 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, variable with automatic storage duration defined outside that lambda-expression, where the reference would be an odr-use. */ + + if (want_rval) + /* Since we're doing an lvalue-rvalue conversion, this might + not be an odr-use, so evaluate the variable directly. */ + return RECUR (DECL_CAPTURED_VARIABLE (t), rval); + if (flags & tf_error) { tree cap = DECL_CAPTURED_VARIABLE (t); error ("lambda capture of %qE is not a constant expression", cap); - if (!want_rval && decl_constant_var_p (cap)) + if (decl_constant_var_p (cap)) inform (input_location, "because it is used as a glvalue"); } return false; diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-constexpr2.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-constexpr2.C new file mode 100644 index 00000000000..b1982ab0506 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-constexpr2.C @@ -0,0 +1,13 @@ +// PR c++/90212 +// { dg-do compile { target c++11 } } + +template<typename T> struct tuple { + constexpr tuple(T&& t) : t(t) { } + int t; +}; + +void foo() { + constexpr tuple<int> v1{1}; + constexpr auto v2 = v1; + [&]{ constexpr auto v2 = v1; }; +} |