From d8af6c203f18b4fd736df9567926589d96f8e0b3 Mon Sep 17 00:00:00 2001
From: Martin Uecker <uecker@tugraz.at>
Date: Thu, 14 Nov 2024 20:54:33 +0100
Subject: [PATCH] c: fix ICE when forming composite type for two structures /
 unions [PR117548]

When forming the composite type from two tagged type, we need to find the
original type for a typedecl to get the correct tag.

	PR c/117548

gcc/c/ChangeLog:
	* c-decl.cc (finish_struct): Add checking assertion.
	* c-typeck.cc (c_type_original): New function.
	(composite_types_internal): Get tag from original type.

gcc/testsuite/ChangeLog:
	* gcc.dg/pr117548.c: New test.
---
 gcc/c/c-decl.cc                 |  3 +++
 gcc/c/c-typeck.cc               | 38 ++++++++++++++++++++-------------
 gcc/testsuite/gcc.dg/pr117548.c | 12 +++++++++++
 3 files changed, 38 insertions(+), 15 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr117548.c

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 07c18a34072..7e65bd04b11 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -9872,6 +9872,9 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
       hashval_t hash = c_struct_hasher::hash (t);
 
       gcc_checking_assert (TYPE_STRUCTURAL_EQUALITY_P (t));
+      gcc_checking_assert (!TYPE_NAME (t)
+			   || TREE_CODE (TYPE_NAME (t)) == IDENTIFIER_NODE);
+
       tree *e = c_struct_htab->find_slot_with_hash (t, hash, INSERT);
       if (*e)
 	TYPE_CANONICAL (t) = *e;
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 10b02da8752..9212a8ebc0a 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -576,6 +576,21 @@ c_build_functype_attribute_variant (tree ntype, tree otype, tree attrs)
 
 }
 
+/* Given a type which could be a typedef name, make sure to return the
+   original type.  */
+static const_tree
+c_type_original (const_tree t)
+{
+  /* It may even be a typedef of a typedef...
+     In the case of compiler-created builtin structs the TYPE_DECL
+     may be a dummy, with no DECL_ORIGINAL_TYPE.  Don't fault.  */
+  while (TYPE_NAME (t)
+	 && TREE_CODE (TYPE_NAME (t)) == TYPE_DECL
+	 && DECL_ORIGINAL_TYPE (TYPE_NAME (t)))
+    t = DECL_ORIGINAL_TYPE (TYPE_NAME (t));
+  return t;
+}
+
 
 /* Return the composite type of two compatible types.
 
@@ -728,8 +743,11 @@ composite_type_internal (tree t1, tree t2, struct composite_cache* cache)
     case UNION_TYPE:
       if (flag_isoc23 && !comptypes_same_p (t1, t2))
 	{
+	  /* Go to the original type to get the right tag.  */
+	  tree tag = TYPE_NAME (c_type_original (const_cast<tree> (t1)));
+
 	  gcc_checking_assert (COMPLETE_TYPE_P (t1) && COMPLETE_TYPE_P (t2));
-	  gcc_checking_assert (!TYPE_NAME (t1) || comptypes (t1, t2));
+	  gcc_checking_assert (!tag || comptypes (t1, t2));
 
 	  /* If a composite type for these two types is already under
 	     construction, return it.  */
@@ -742,7 +760,7 @@ composite_type_internal (tree t1, tree t2, struct composite_cache* cache)
 
 	  tree n = make_node (code1);
 	  SET_TYPE_STRUCTURAL_EQUALITY (n);
-	  TYPE_NAME (n) = TYPE_NAME (t1);
+	  TYPE_NAME (n) = tag;
 
 	  struct composite_cache cache2 = { t1, t2, n, cache };
 	  cache = &cache2;
@@ -1781,19 +1799,9 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
 
   /* We have to verify that the tags of the types are the same.  This
      is harder than it looks because this may be a typedef, so we have
-     to go look at the original type.  It may even be a typedef of a
-     typedef...
-     In the case of compiler-created builtin structs the TYPE_DECL
-     may be a dummy, with no DECL_ORIGINAL_TYPE.  Don't fault.  */
-  while (TYPE_NAME (t1)
-	 && TREE_CODE (TYPE_NAME (t1)) == TYPE_DECL
-	 && DECL_ORIGINAL_TYPE (TYPE_NAME (t1)))
-    t1 = DECL_ORIGINAL_TYPE (TYPE_NAME (t1));
-
-  while (TYPE_NAME (t2)
-	 && TREE_CODE (TYPE_NAME (t2)) == TYPE_DECL
-	 && DECL_ORIGINAL_TYPE (TYPE_NAME (t2)))
-    t2 = DECL_ORIGINAL_TYPE (TYPE_NAME (t2));
+     to go look at the original type.  */
+  t1 = c_type_original (t1);
+  t2 = c_type_original (t2);
 
   if (TYPE_NAME (t1) != TYPE_NAME (t2))
     return false;
diff --git a/gcc/testsuite/gcc.dg/pr117548.c b/gcc/testsuite/gcc.dg/pr117548.c
new file mode 100644
index 00000000000..d388d2587c3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr117548.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+typedef struct A { int q; } A;
+void f(A*);
+
+int main(void)
+{
+  struct A { int q; };
+  void f(struct A*);
+}
+