When streaming in the artificial VAR_DECL synthesized for a class NTTP
argument, we end up crashing from complete_vars because the call to
maybe_register_incomplete_var from add_module_namespace_decl for this
VAR_DECL pushes an unexpected NULL_TREE type onto the incomplete_vars
vector.
This patch fixes this by checking for NULL_TREE before pushing onto
the vector. This avoids the crash, but I noticed we still appear to
mishandle these artificial VAR_DECLs across translation units: the lookup
from get_template_parm_object for an existing VAR_DECL for the given
class NTTP argument fails to find the streamed-in VAR_DECL from the
other translation unit, so we end up creating a second VAR_DECL, but
that causes specialization equivalency issues in the XFAIL'd part of the
below test. I'm afraid I don't understand why the lookup fails here
despite having done add_module_namespace_decl during stream-in, but
fixing the ICE seems like a safe and useful step towards enabling class
NTTP arguments used in modules.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
PR c++/100616
gcc/cp/ChangeLog:
* decl.cc (maybe_register_incomplete_var): Check result of
outermost_open_class.
gcc/testsuite/ChangeLog:
* g++.dg/modules/pr100616_a.C: New test.
* g++.dg/modules/pr100616_b.C: New test.
---
gcc/cp/decl.cc | 8 +++++---
gcc/testsuite/g++.dg/modules/pr100616_a.C | 8 ++++++++
gcc/testsuite/g++.dg/modules/pr100616_b.C | 10 ++++++++++
3 files changed, 23 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/modules/pr100616_a.C
create mode 100644 gcc/testsuite/g++.dg/modules/pr100616_b.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 80467c19254..722b64793ed 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -18235,9 +18235,11 @@ maybe_register_incomplete_var (tree var)
{
/* When the outermost open class is complete we can resolve any
pointers-to-members. */
- tree context = outermost_open_class ();
- incomplete_var iv = {var, context};
- vec_safe_push (incomplete_vars, iv);
+ if (tree context = outermost_open_class ())
+ {
+ incomplete_var iv = {var, context};
+ vec_safe_push (incomplete_vars, iv);
+ }
}
}
}
diff --git a/gcc/testsuite/g++.dg/modules/pr100616_a.C
b/gcc/testsuite/g++.dg/modules/pr100616_a.C
new file mode 100644
index 00000000000..788af2eb533
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr100616_a.C
@@ -0,0 +1,8 @@
+// PR c++/100616
+// { dg-additional-options "-std=c++20 -fmodules-ts" }
+// { dg-module-cmi pr100616 }
+export module pr100616;
+
+template<auto> struct C { };
+struct A { };
+C<A{}> c1;
diff --git a/gcc/testsuite/g++.dg/modules/pr100616_b.C
b/gcc/testsuite/g++.dg/modules/pr100616_b.C
new file mode 100644
index 00000000000..8037ceda3ed
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr100616_b.C
@@ -0,0 +1,10 @@
+// PR c++/100616
+// { dg-additional-options "-std=c++20 -fmodules-ts" }
+module pr100616;
+
+C<A{}> c2;
+
+// FIXME: We don't reuse the artificial VAR_DECL for the class NTTP argument
A{}
+// from the other translation unit, which causes these types to be different.
+using ty_a = decltype(c1);
+using ty_a = decltype(c2); // { dg-bogus "conflicting" "" { xfail *-*-* } }
--
2.38.0.rc0.52.gdda7228a83
