| Message ID | 20240302005824.924155-1-polacek@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: lambda capturing structured bindings [PR85889] | expand |
On Fri, Mar 01, 2024 at 07:58:24PM -0500, Marek Polacek wrote: > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for 15? (Or even trunk?) > > -- >8 -- > <https://wg21.link/p1381r1> clarifies that it's OK to capture structured > bindings. > > [expr.prim.lambda.capture]/4 says "The identifier in a simple-capture shall > denote a local entity" and [basic.pre]/3: "An entity is a [...] structured > binding". > > It doesn't appear that this was made a DR, so, strictly speaking, we > should have a -Wc++20-extensions warning, like clang++. > > PR c++/85889 > > gcc/cp/ChangeLog: > > * lambda.cc (add_capture): Add a pedwarn for capturing structured > bindings. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/decomp3.C: Use -Wno-c++20-extensions. > * g++.dg/cpp1z/decomp60.C: New test. > --- > gcc/cp/lambda.cc | 9 +++++++++ > gcc/testsuite/g++.dg/cpp1z/decomp60.C | 12 ++++++++++++ > gcc/testsuite/g++.dg/cpp2a/decomp3.C | 2 +- > 3 files changed, 22 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp1z/decomp60.C > > diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc > index 4b1f9391fee..470f9d2c4f1 100644 > --- a/gcc/cp/lambda.cc > +++ b/gcc/cp/lambda.cc > @@ -607,6 +607,15 @@ add_capture (tree lambda, tree id, tree orig_init, bool by_reference_p, > TCTX_CAPTURE_BY_COPY, type)) > return error_mark_node; > } > + > + if (cxx_dialect < cxx20) > + { > + tree stripped_init = tree_strip_any_location_wrapper (initializer); I was missing an auto_diagnostic_group here. Fixed. > + if (DECL_DECOMPOSITION_P (stripped_init) > + && pedwarn (input_location, OPT_Wc__20_extensions, > + "captured structured bindings are a C++20 extension")) > + inform (DECL_SOURCE_LOCATION (stripped_init), "declared here");
On 3/4/24 12:49, Marek Polacek wrote: > On Fri, Mar 01, 2024 at 07:58:24PM -0500, Marek Polacek wrote: >> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for 15? (Or even trunk?) >> >> -- >8 -- >> <https://wg21.link/p1381r1> clarifies that it's OK to capture structured >> bindings. >> >> [expr.prim.lambda.capture]/4 says "The identifier in a simple-capture shall >> denote a local entity" and [basic.pre]/3: "An entity is a [...] structured >> binding". >> >> It doesn't appear that this was made a DR, so, strictly speaking, we >> should have a -Wc++20-extensions warning, like clang++. >> >> PR c++/85889 >> >> gcc/cp/ChangeLog: >> >> * lambda.cc (add_capture): Add a pedwarn for capturing structured >> bindings. >> >> gcc/testsuite/ChangeLog: >> >> * g++.dg/cpp2a/decomp3.C: Use -Wno-c++20-extensions. >> * g++.dg/cpp1z/decomp60.C: New test. >> --- >> gcc/cp/lambda.cc | 9 +++++++++ >> gcc/testsuite/g++.dg/cpp1z/decomp60.C | 12 ++++++++++++ >> gcc/testsuite/g++.dg/cpp2a/decomp3.C | 2 +- >> 3 files changed, 22 insertions(+), 1 deletion(-) >> create mode 100644 gcc/testsuite/g++.dg/cpp1z/decomp60.C >> >> diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc >> index 4b1f9391fee..470f9d2c4f1 100644 >> --- a/gcc/cp/lambda.cc >> +++ b/gcc/cp/lambda.cc >> @@ -607,6 +607,15 @@ add_capture (tree lambda, tree id, tree orig_init, bool by_reference_p, >> TCTX_CAPTURE_BY_COPY, type)) >> return error_mark_node; >> } >> + >> + if (cxx_dialect < cxx20) >> + { >> + tree stripped_init = tree_strip_any_location_wrapper (initializer); > > I was missing an auto_diagnostic_group here. Fixed. OK for 15 with that fix. >> + if (DECL_DECOMPOSITION_P (stripped_init) >> + && pedwarn (input_location, OPT_Wc__20_extensions, >> + "captured structured bindings are a C++20 extension")) >> + inform (DECL_SOURCE_LOCATION (stripped_init), "declared here"); >
diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc index 4b1f9391fee..470f9d2c4f1 100644 --- a/gcc/cp/lambda.cc +++ b/gcc/cp/lambda.cc @@ -607,6 +607,15 @@ add_capture (tree lambda, tree id, tree orig_init, bool by_reference_p, TCTX_CAPTURE_BY_COPY, type)) return error_mark_node; } + + if (cxx_dialect < cxx20) + { + tree stripped_init = tree_strip_any_location_wrapper (initializer); + if (DECL_DECOMPOSITION_P (stripped_init) + && pedwarn (input_location, OPT_Wc__20_extensions, + "captured structured bindings are a C++20 extension")) + inform (DECL_SOURCE_LOCATION (stripped_init), "declared here"); + } } /* Add __ to the beginning of the field name so that user code diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp60.C b/gcc/testsuite/g++.dg/cpp1z/decomp60.C new file mode 100644 index 00000000000..b6117f3af58 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/decomp60.C @@ -0,0 +1,12 @@ +// PR c++/85889 +// { dg-do compile { target c++17 } } +// { dg-options "" } + +struct X { int i, j; }; +void f() { + X x{}; + auto [i, j] = x; + [&i]() { }; // { dg-warning "captured structured bindings" "" { target c++17_only } } + [i]() { }; // { dg-warning "captured structured bindings" "" { target c++17_only } } +} + diff --git a/gcc/testsuite/g++.dg/cpp2a/decomp3.C b/gcc/testsuite/g++.dg/cpp2a/decomp3.C index 5e77973d41f..25ab8319975 100644 --- a/gcc/testsuite/g++.dg/cpp2a/decomp3.C +++ b/gcc/testsuite/g++.dg/cpp2a/decomp3.C @@ -1,6 +1,6 @@ // P1381R1 // { dg-do compile { target c++11 } } -// { dg-options "" } +// { dg-options "-Wno-c++20-extensions" } struct Foo { int a : 1; int b; };