From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Wed, 14 May 2025 10:49:22 +0000 (+1000)
Subject: c++: Partially revert "Support lambdas attached to more places in modules" [PR118245]
X-Git-Tag: releases/gcc-14.3.0~16
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a16584beb312bfc493977e472dcb9d11ad5bc76;p=thirdparty%2Fgcc.git

c++: Partially revert "Support lambdas attached to more places in modules" [PR118245]

r14-9232-g3685fae23bb008 broke the ABI for lambdas in base classes,
causing ICEs when different lambdas got given the same mangled name.

This patch reverts the parser.cc changes from that patch to restore the
old behaviour.  The properly fixed behaviour is available in GCC 15.1
with r15-7202-g8990070b4297b9, but that change was not suitable for
backporting.

	PR c++/118245

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_class_head): Remove lambda scope when
	parsing base classes.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/lambda-7_a.H: Expect the test to fail.
	* g++.dg/modules/lambda-7_b.C: Likewise.
	* g++.dg/modules/lambda-7_c.C: Likewise.
	* g++.dg/cpp2a/lambda-uneval23.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index ae97ae5c5f5..4a2c1f272a3 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -27750,16 +27750,10 @@ cp_parser_class_head (cp_parser* parser,
   if (cp_lexer_next_token_is (parser->lexer, CPP_COLON))
     {
       if (type)
-	{
-	  pushclass (type);
-	  start_lambda_scope (TYPE_NAME (type));
-	}
+	pushclass (type);
       bases = cp_parser_base_clause (parser);
       if (type)
-	{
-	  finish_lambda_scope ();
-	  popclass ();
-	}
+	popclass ();
     }
   else
     bases = NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C
new file mode 100644
index 00000000000..fa009f53ff2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C
@@ -0,0 +1,7 @@
+// PR c++/118245
+// { dg-do compile { target c++20 } }
+
+template<auto> struct Cask {};
+struct T1 : Cask<[]{}> {
+  Cask<[]{}> c{};
+};
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_a.H b/gcc/testsuite/g++.dg/modules/lambda-7_a.H
index 5197114f76c..842aedc5fd9 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_a.H
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_a.H
@@ -1,4 +1,4 @@
 // { dg-additional-options "-fmodule-header -Wno-subobject-linkage" }
-// { dg-module-cmi {} }
+// { dg-ice "see PR c++/118245" { c++20 } }
 
 #include "lambda-7.h"
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_b.C b/gcc/testsuite/g++.dg/modules/lambda-7_b.C
index 2d781e93067..cd4d0f3aa65 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_b.C
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_b.C
@@ -1,4 +1,5 @@
 // { dg-additional-options "-fmodules-ts -fno-module-lazy -Wno-subobject-linkage" }
+// { dg-xfail-if "see PR c++/118245" { c++20 } }
 // Test for ODR deduplication
 
 #include "lambda-7.h"
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_c.C b/gcc/testsuite/g++.dg/modules/lambda-7_c.C
index f283681fa96..3fd159e08a7 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_c.C
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_c.C
@@ -1,5 +1,5 @@
-// { dg-module-do run }
 // { dg-additional-options "-fmodules-ts -fno-module-lazy -Wno-subobject-linkage" }
+// { dg-xfail-if "see PR c++/118245" { c++20 } }
 
 import "lambda-7_a.H";