Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
Here we instantiate the lambda three times in producing A<0>::f:
1) in tsubst_function_type, substituting the type of A<>::f
2) in tsubst_function_decl, substituting the parameters of A<>::f
3) in regenerate_decl_from_template when instantiating A<>::f
The first one gets thrown away by maybe_rebuild_function_decl_type. Before
r15-7202, we happily built all of them and mangled the result wrongly as
lambda #3. After r15-7202, we try to mangle #3 as #1, which breaks because
#1 is already mangled as #1.
This patch avoids building #3 by suppressing regenerate_decl_from_template
if the template signature includes a lambda, fixing the ICE.
We now mangle the lambda as #2, which is still wrong. Addressing that
should involve not calling tsubst_function_type from tsubst_function_decl,
and building the type from the parms types in the first place rather than
fixing it up in maybe_rebuild_function_decl_type.
PR c++/119401
gcc/cp/ChangeLog:
* pt.cc (regenerate_decl_from_template): Don't regenerate if the
signature involves a lambda.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/lambda-targ11.C: New test.
---
gcc/cp/pt.cc | 13 +++++++++++++
gcc/testsuite/g++.dg/cpp2a/lambda-targ11.C | 13 +++++++++++++
gcc/testsuite/g++.dg/cpp2a/lambda-targ12.C | 13 +++++++++++++
3 files changed, 39 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-targ11.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-targ12.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 417d107d699..f7c56a10794 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27238,6 +27238,19 @@ regenerate_decl_from_template (tree decl, tree tmpl,
tree args)
if (DECL_UNIQUE_FRIEND_P (decl))
goto done;
+ /* A template with a lambda in the signature also changes type if
+ regenerated (PR119401). */
+ walk_tree_fn find_lambda
+ = [](tree *tp, int *, void *)
+ {
+ if (TREE_CODE (*tp) == LAMBDA_EXPR)
+ return *tp;
+ return NULL_TREE;
+ };
+ if (cp_walk_tree_without_duplicates
+ (&TREE_TYPE (tmpl), find_lambda, nullptr))
+ goto done;
+
/* Use the source location of the definition. */
DECL_SOURCE_LOCATION (decl) = DECL_SOURCE_LOCATION (tmpl);
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-targ11.C
b/gcc/testsuite/g++.dg/cpp2a/lambda-targ11.C
new file mode 100644
index 00000000000..9f2f743b7eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-targ11.C
@@ -0,0 +1,13 @@
+// PR c++/119401
+// { dg-do compile { target c++20 } }
+
+template <auto>
+struct B {};
+template <int N>
+struct A {
+ void f(B<[]{}>) {}
+};
+auto t = &A<0>::f;
+
+// A<0>::f(B<A<0>::{lambda()#1}{}>)
+// { dg-final { scan-assembler "_ZN1AILi0EE1fE1BIXtlNS0_UlvE_EEEE" { xfail
*-*-* } } }
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-targ12.C
b/gcc/testsuite/g++.dg/cpp2a/lambda-targ12.C
new file mode 100644
index 00000000000..bb3f701967f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-targ12.C
@@ -0,0 +1,13 @@
+// PR c++/119401
+// { dg-do compile { target c++20 } }
+
+template <class>
+struct B {};
+template <int N>
+struct A {
+ void f(B<decltype([]{})>) {}
+};
+auto t = &A<0>::f;
+
+// A<0>::f(B<A<0>::{lambda()#1}>)
+// { dg-final { scan-assembler "_ZN1AILi0EE1fE1BINS0_UlvE_EE" { xfail *-*-* }
} }
base-commit: 95c25cb09f58810bc520c3db469945c6a751aa32
--
2.49.0
