| Message ID | 20200412134833.2053141-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Infinite diagnostic loop with decltype([]{}) [PR94521] | expand |
On 4/12/20 9:48 AM, Patrick Palka wrote: > We are hitting a recursive loop when printing the signature of a function > containing a decltype([]{}) type. The loop is > > dump_function_decl -> dump_substitution > -> dump_template_bindings > -> dump_type > -> dump_aggr_type > -> dump_scope -> dump_function_decl > > and we loop because dump_template_bindings wants to print the resolved type of > decltype([]{}) (i.e. just a lambda type), so it calls dump_aggr_type, which > wants to print the function scope of the lambda type. But the function scope of > the lambda type is the function which we're in the middle of printing. > > This patch breaks the loop by passing TFF_NO_FUNCTION_ARGUMENTS to > dump_function_decl from dump_scope, so that we avoid recursing into > dump_substitution and ultimately looping. > > This also means we no longer print a "[with ...]" clause when printing a > function template scope, and we instead just print its template argument list in > a more natural way, e.g. instead of > foo(int, char) [with T=bool]::x > we would now print > foo<bool>::x > which seems like an improvement on its own. Hmm. That no longer distinguishes between multiple template overloads of foo, but I suppose we should always print the full function as part of the same diagnostic, so having a terser form here is OK. > The full signature of the function 'spam' in the below testcase is now > void spam(decltype (<lambda>)*) [with T = int; decltype (<lambda>) = spam<int>::<lambda()>] > > Successfully bootstrapped and regtested on x86_64-pc-linux-gnu, does this look > OK to commit? OK. > gcc/cp/ChangeLog: > > PR c++/94521 > * error.c (dump_scope): Pass TFF_NO_FUNCTION_ARGUMENTS to > dump_function_decl when printing a function template instantiation as a > scope. > > gcc/testsuite/ChangeLog: > > PR c++/94521 > * g++.dg/cpp2a/lambda-uneval12.C: New test. > --- > gcc/cp/error.c | 2 ++ > gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C | 13 +++++++++++++ > 2 files changed, 15 insertions(+) > create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C > > diff --git a/gcc/cp/error.c b/gcc/cp/error.c > index 61d1218dc90..98c163db572 100644 > --- a/gcc/cp/error.c > +++ b/gcc/cp/error.c > @@ -211,6 +211,8 @@ dump_scope (cxx_pretty_printer *pp, tree scope, int flags) > } > else if ((flags & TFF_SCOPE) && TREE_CODE (scope) == FUNCTION_DECL) > { > + if (DECL_USE_TEMPLATE (scope)) > + f |= TFF_NO_FUNCTION_ARGUMENTS; > dump_function_decl (pp, scope, f); > pp_cxx_colon_colon (pp); > } > diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C > new file mode 100644 > index 00000000000..24d2e701e44 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C > @@ -0,0 +1,13 @@ > +// PR c++/94521 > +// { dg-do compile { target c++2a } } > + > +template <typename T> > +void spam(decltype([]{}) *s) > +{ > + static_assert(__is_same(int, decltype(s))); // { dg-error "static assertion failed" } > +} > + > +void foo() > +{ > + spam<int>(nullptr); > +} >
diff --git a/gcc/cp/error.c b/gcc/cp/error.c index 61d1218dc90..98c163db572 100644 --- a/gcc/cp/error.c +++ b/gcc/cp/error.c @@ -211,6 +211,8 @@ dump_scope (cxx_pretty_printer *pp, tree scope, int flags) } else if ((flags & TFF_SCOPE) && TREE_CODE (scope) == FUNCTION_DECL) { + if (DECL_USE_TEMPLATE (scope)) + f |= TFF_NO_FUNCTION_ARGUMENTS; dump_function_decl (pp, scope, f); pp_cxx_colon_colon (pp); } diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C new file mode 100644 index 00000000000..24d2e701e44 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C @@ -0,0 +1,13 @@ +// PR c++/94521 +// { dg-do compile { target c++2a } } + +template <typename T> +void spam(decltype([]{}) *s) +{ + static_assert(__is_same(int, decltype(s))); // { dg-error "static assertion failed" } +} + +void foo() +{ + spam<int>(nullptr); +}
We are hitting a recursive loop when printing the signature of a function containing a decltype([]{}) type. The loop is dump_function_decl -> dump_substitution -> dump_template_bindings -> dump_type -> dump_aggr_type -> dump_scope -> dump_function_decl and we loop because dump_template_bindings wants to print the resolved type of decltype([]{}) (i.e. just a lambda type), so it calls dump_aggr_type, which wants to print the function scope of the lambda type. But the function scope of the lambda type is the function which we're in the middle of printing. This patch breaks the loop by passing TFF_NO_FUNCTION_ARGUMENTS to dump_function_decl from dump_scope, so that we avoid recursing into dump_substitution and ultimately looping. This also means we no longer print a "[with ...]" clause when printing a function template scope, and we instead just print its template argument list in a more natural way, e.g. instead of foo(int, char) [with T=bool]::x we would now print foo<bool>::x which seems like an improvement on its own. The full signature of the function 'spam' in the below testcase is now void spam(decltype (<lambda>)*) [with T = int; decltype (<lambda>) = spam<int>::<lambda()>] Successfully bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to commit? gcc/cp/ChangeLog: PR c++/94521 * error.c (dump_scope): Pass TFF_NO_FUNCTION_ARGUMENTS to dump_function_decl when printing a function template instantiation as a scope. gcc/testsuite/ChangeLog: PR c++/94521 * g++.dg/cpp2a/lambda-uneval12.C: New test. --- gcc/cp/error.c | 2 ++ gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C | 13 +++++++++++++ 2 files changed, 15 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-uneval12.C