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);
+}
