[gcc r13-331] c++: fix arm-eabi bootstrap [PR105567]

[gcc r13-331] c++: fix arm-eabi bootstrap [PR105567]

[Jason Merrill]

https://gcc.gnu.org/g:4dc86f716fe6087f1cf786d69c0c6f3f5af810f0

commit r13-331-g4dc86f716fe6087f1cf786d69c0c6f3f5af810f0
Author: Jason Merrill <jason@redhat.com>
Date:   Wed May 11 09:44:57 2022 -0400

    c++: fix arm-eabi bootstrap [PR105567]
    
    Since my r13-112, in the template we were changing 'return' to 'return this'
    on cdtor_returns_this targets, and then getting confused by that when
    instantiating.  So only make that change at instantiation time.
    
            PR bootstrap/105567
    
    gcc/cp/ChangeLog:
    
            * typeck.cc (check_return_expr): Don't mess with ctor return value
            while parsing a template.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/template/ctor10.C: New test.

Diff:
---
 gcc/cp/typeck.cc                       |  4 ++--
 gcc/testsuite/g++.dg/template/ctor10.C | 10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 57e55ed48d1..6ecdd97697d 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10448,7 +10448,7 @@ check_return_expr (tree retval, bool *no_warning)
       if (retval)
 	error_at (loc, "returning a value from a destructor");
 
-      if (targetm.cxx.cdtor_returns_this ())
+      if (targetm.cxx.cdtor_returns_this () && !processing_template_decl)
 	retval = current_class_ptr;
       else
 	return NULL_TREE;
@@ -10463,7 +10463,7 @@ check_return_expr (tree retval, bool *no_warning)
 	/* You can't return a value from a constructor.  */
 	error_at (loc, "returning a value from a constructor");
 
-      if (targetm.cxx.cdtor_returns_this ())
+      if (targetm.cxx.cdtor_returns_this () && !processing_template_decl)
 	retval = current_class_ptr;
       else
 	return NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/template/ctor10.C b/gcc/testsuite/g++.dg/template/ctor10.C
new file mode 100644
index 00000000000..cf10fc5b19a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ctor10.C
@@ -0,0 +1,10 @@
+// PR bootstrap/105567
+// This was breaking with cdtor_returns_this.
+
+template <class T>
+struct A
+{
+  A() { return; }
+};
+
+A<int> a;