[gcc r13-6668] d: Fix undefined reference to lambda defined in private enum [PR109108]

[Iain Buclaw <ibuclaw@gcc.gnu.org>]

https://gcc.gnu.org/g:423d34f61c43e400f0d5b837fe93c83963b2ecdd

commit r13-6668-g423d34f61c43e400f0d5b837fe93c83963b2ecdd
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Tue Mar 14 13:16:11 2023 +0100

    d: Fix undefined reference to lambda defined in private enum [PR109108]
    
    Previously lambdas were connected to the module they were defined in.
    Now they are emitted into every referencing compilation unit, and are
    given one-only linkage.
    
            PR d/109108
    
    gcc/d/ChangeLog:
    
            * decl.cc (function_defined_in_root_p): Remove.
            (get_symbol_decl): Set DECL_LAMBDA_FUNCTION_P on function literals.
            (start_function): Unconditionally unset DECL_EXTERNAL
            (set_linkage_for_decl): Give lambda functions one-only linkage.
    
    gcc/testsuite/ChangeLog:
    
            * gdc.dg/torture/imports/pr109108.d: New test.
            * gdc.dg/torture/pr109108.d: New test.

Diff:
---
 gcc/d/decl.cc                                   | 41 ++++++++-----------------
 gcc/testsuite/gdc.dg/torture/imports/pr109108.d | 11 +++++++
 gcc/testsuite/gdc.dg/torture/pr109108.d         | 10 ++++++
 3 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/gcc/d/decl.cc b/gcc/d/decl.cc
index c451805639d..4fbabd59998 100644
--- a/gcc/d/decl.cc
+++ b/gcc/d/decl.cc
@@ -1090,25 +1090,6 @@ build_decl_tree (Dsymbol *d)
   input_location = saved_location;
 }
 
-/* Returns true if function FD, or any lexically enclosing scope function of FD
-   is defined or instantiated in a root module.  */
-
-static bool
-function_defined_in_root_p (FuncDeclaration *fd)
-{
-  Module *md = fd->getModule ();
-  if (md && md->isRoot ())
-    return true;
-
-  for (TemplateInstance *ti = fd->isInstantiated (); ti != NULL; ti = ti->tinst)
-    {
-      if (ti->minst && ti->minst->isRoot ())
-	return true;
-    }
-
-  return false;
-}
-
 /* Returns true if function FD always needs to be implicitly defined, such as
    it was declared `pragma(inline)'.  */
 
@@ -1474,6 +1455,12 @@ get_symbol_decl (Declaration *decl)
 	  DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (decl->csym) = 1;
 	}
 
+      /* In [expression/function_literals], function literals (aka lambdas)
+	 enable embedding anonymous functions and anonymous delegates directly
+	 into expressions.  They are defined in each referencing module.  */
+      if (fd->isFuncLiteralDeclaration ())
+	DECL_SET_LAMBDA_FUNCTION (decl->csym, true);
+
       /* Mark compiler generated functions as artificial.  */
       if (fd->isGenerated ())
 	DECL_ARTIFICIAL (decl->csym) = 1;
@@ -2029,12 +2016,9 @@ start_function (FuncDeclaration *fd)
 {
   tree fndecl = get_symbol_decl (fd);
 
-  /* Function has been defined, check now whether we intend to send it to
-     object file, or it really is extern.  Such as inlinable functions from
-     modules not in this compilation, or thunk aliases.  */
-  if (function_defined_in_root_p (fd))
-    DECL_EXTERNAL (fndecl) = 0;
-
+  /* Function has been defined. Whether we intend to send it to object file, or
+     discard it has already been determined by set_linkage_for_decl.  */
+  DECL_EXTERNAL (fndecl) = 0;
   DECL_INITIAL (fndecl) = error_mark_node;
 
   /* Add this decl to the current binding level.  */
@@ -2550,9 +2534,10 @@ set_linkage_for_decl (tree decl)
   if (!TREE_PUBLIC (decl))
     return;
 
-  /* Functions declared as `pragma(inline, true)' can appear in multiple
-     translation units.  */
-  if (TREE_CODE (decl) == FUNCTION_DECL && DECL_DECLARED_INLINE_P (decl))
+  /* Function literals and functions declared as `pragma(inline, true)' can
+     appear in multiple translation units.  */
+  if (TREE_CODE (decl) == FUNCTION_DECL
+      && (DECL_DECLARED_INLINE_P (decl) || DECL_LAMBDA_FUNCTION_P (decl)))
     return d_comdat_linkage (decl);
 
   /* Don't need to give private or protected symbols a special linkage.  */
diff --git a/gcc/testsuite/gdc.dg/torture/imports/pr109108.d b/gcc/testsuite/gdc.dg/torture/imports/pr109108.d
new file mode 100644
index 00000000000..cec5274098c
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/torture/imports/pr109108.d
@@ -0,0 +1,11 @@
+module imports.pr109108;
+private enum int function(ref int)[] funs =
+[
+    0: (ref idx) => 0,
+    1: (ref idx) => 1,
+];
+
+int test109108(I)(I idx)
+{
+    return funs[idx](idx);
+}
diff --git a/gcc/testsuite/gdc.dg/torture/pr109108.d b/gcc/testsuite/gdc.dg/torture/pr109108.d
new file mode 100644
index 00000000000..4a428bf85a6
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/torture/pr109108.d
@@ -0,0 +1,10 @@
+// { dg-additional-files "imports/pr109108.d" }
+// { dg-additional-options "-I[srcdir] -fno-moduleinfo" }
+// { dg-do link }
+// { dg-skip-if "needs gcc/config.d" { ! d_runtime } }
+import imports.pr109108;
+
+extern(C) int main()
+{
+    return test109108(0);
+}