[PATCH RFA] c-family: attribute ((aligned, mode)) [PR100545]

[Jason Merrill <jason@redhat.com>]

The problem here was that handle_mode_attribute clobbered the changes of any
previous attribute, only copying type qualifiers to the new type.  And
common_handle_aligned_attribute had previously set up the typedef, so when
we later called set_underlying_type it saw DECL_ORIGINAL_TYPE set and just
returned, even though handle_mode_attribute had messed up the TREE_TYPE.
So, let's fix handle_mode_attribute to copy attributes, alignment, and
typedefness to the new type.

Tested x86_64-pc-linux-gnu, OK for trunk now or after 12.1?

	PR c/100545

gcc/c-family/ChangeLog:

	* c-attribs.cc (handle_mode_attribute): Copy attributes, aligned,
	and typedef.
	* c-common.cc (set_underlying_type): Add assert.

gcc/testsuite/ChangeLog:

	* c-c++-common/attr-mode-1.c: New test.
---
 gcc/c-family/c-attribs.cc                | 15 ++++++++++++++-
 gcc/c-family/c-common.cc                 |  7 ++++---
 gcc/testsuite/c-c++-common/attr-mode-1.c |  3 +++
 3 files changed, 21 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/attr-mode-1.c

diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 111a33f405a..26876d0f309 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -2199,7 +2199,20 @@ handle_mode_attribute (tree *node, tree name, tree args,
 	  return NULL_TREE;
 	}
 
-      *node = build_qualified_type (typefm, TYPE_QUALS (type));
+      /* Copy any quals and attributes to the new type.  */
+      *node = build_type_attribute_qual_variant (typefm, TYPE_ATTRIBUTES (type),
+						 TYPE_QUALS (type));
+      if (TYPE_USER_ALIGN (type))
+	*node = build_aligned_type (*node, TYPE_ALIGN (type));
+      if (typedef_variant_p (type))
+	{
+	  /* Set up the typedef all over again.  */
+	  tree decl = TYPE_NAME (type);
+	  DECL_ORIGINAL_TYPE (decl) = NULL_TREE;
+	  TREE_TYPE (decl) = *node;
+	  set_underlying_type (decl);
+	  *node = TREE_TYPE (decl);
+	}
     }
 
   return NULL_TREE;
diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
index bb0544eeaea..730faa9e87f 100644
--- a/gcc/c-family/c-common.cc
+++ b/gcc/c-family/c-common.cc
@@ -8153,15 +8153,16 @@ check_missing_format_attribute (tree ltype, tree rtype)
 void
 set_underlying_type (tree x)
 {
-  if (x == error_mark_node)
+  if (x == error_mark_node || TREE_TYPE (x) == error_mark_node)
     return;
   if (DECL_IS_UNDECLARED_BUILTIN (x) && TREE_CODE (TREE_TYPE (x)) != ARRAY_TYPE)
     {
       if (TYPE_NAME (TREE_TYPE (x)) == 0)
 	TYPE_NAME (TREE_TYPE (x)) = x;
     }
-  else if (TREE_TYPE (x) != error_mark_node
-	   && DECL_ORIGINAL_TYPE (x) == NULL_TREE)
+  else if (DECL_ORIGINAL_TYPE (x))
+    gcc_checking_assert (TYPE_NAME (TREE_TYPE (x)) == x);
+  else
     {
       tree tt = TREE_TYPE (x);
       DECL_ORIGINAL_TYPE (x) = tt;
diff --git a/gcc/testsuite/c-c++-common/attr-mode-1.c b/gcc/testsuite/c-c++-common/attr-mode-1.c
new file mode 100644
index 00000000000..59b20cd99e8
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/attr-mode-1.c
@@ -0,0 +1,3 @@
+// PR c/100545
+
+typedef int fatp_t __attribute__((aligned, mode(SI)));

base-commit: 6a460a2007dd9c527c5f9d5bbbedb852db7c1373
-- 
2.27.0