c: Fix bug in typedef redefinitions of tagged types [PR118765]

When we redefine a tagged type we incorrectly update TYPE_STUB_DECL
of the previously defined type instead of the new one.  Because
TYPE_STUB_DECL is used when determining whether two such types are
the same, this can cause valid typedef redefinitions to be rejected
later. This is only a partial fix for PR118765.

	PR c/118765

gcc/c/ChangeLog:
	* c-decl.cc (finish_struct,finish_enum): Swap direction when
	copying TYPE_STRUB_DECL in redefinitions.

gcc/testsuite/ChangeLog:
	* gcc.dg/pr118765.c: New test.

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 0dcbae9b26f573630621cdfa54044dcda581179f..1ae520828c348cefb11dfbc544c609981028e434 100644 (file)
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -9846,7 +9846,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
          && TREE_CODE (vistype) == TREE_CODE (t)
          && !C_TYPE_BEING_DEFINED (vistype))
        {
-         TYPE_STUB_DECL (vistype) = TYPE_STUB_DECL (t);
+         TYPE_STUB_DECL (t) = TYPE_STUB_DECL (vistype);
          if (c_type_variably_modified_p (t))
            {
              error ("redefinition of struct or union %qT with variably "
@@ -10321,7 +10321,7 @@ finish_enum (tree enumtype, tree values, tree attributes)
          && TREE_CODE (vistype) == TREE_CODE (enumtype)
          && !C_TYPE_BEING_DEFINED (vistype))
        {
-         TYPE_STUB_DECL (vistype) = TYPE_STUB_DECL (enumtype);
+         TYPE_STUB_DECL (enumtype) = TYPE_STUB_DECL (vistype);
          if (!comptypes_same_p (enumtype, vistype))
            error("conflicting redefinition of enum %qT", enumtype);
        }

diff --git a/gcc/testsuite/gcc.dg/pr118765.c b/gcc/testsuite/gcc.dg/pr118765.c
new file mode 100644 (file)
index 0000000..12d0259
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr118765.c
@@ -0,0 +1,7 @@
+/* { dg-do "compile" } */
+/* { dg-options "-std=gnu23" } */
+
+typedef struct q { int x; } q_t;
+struct q { int x; };
+typedef struct q { int x; } q_t;
+