Fix TYPE_MAIN_VARIANT construction for arrays of qualified typedefs (PR c/68162).

PR c/68162 reports a spurious warning about incompatible types
involving arrays of const double, constructed in one place using a
typedef for const double and in another place literally using const
double.

The problem is that the array of the typedef was incorrectly
constructed without a TYPE_MAIN_VARIANT being an array of unqualified
elements as it should be (though it seems some more recent change
resulted in this producing incorrect diagnostics, likely the support
for C++-style handling of arrays of qualified type).  This patch fixes
the logic in grokdeclarator to determine first_non_attr_kind, which is
used to determine whether it is necessary to use the TYPE_MAIN_VARIANT
of the type in the declaration specifiers.

However, fixing that logic introduces a failure of
gcc.dg/debug/dwarf2/pr47939-4.c, a test introduced along with
first_non_attr_kind.  Thus, it is necessary to track the original
qualified typedef when qualifying an array type, to use it rather than
a newly-constructed type, to avoid regressing regarding typedef names
in debug info.  This is done along lines I suggested in
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47939#c6>: track the
original type and the number of levels of array indirection at which
it appears, and, in possibly affected cases, pass extra arguments to
c_build_qualified_type (with default arguments to avoid needing to
pass those extra arguments explicitly everywhere).  Given Richard's
recent fix to dwarf2out.c, this allows the C bug to be fixed without
causing debug information regressions.

Bootstrapped with no regressions on x86_64-pc-linux-gnu.

gcc/c:
	PR c/68162
	* c-decl.c (grokdeclarator): Set first_non_attr_kind before
	following link from declarator to next declarator.  Track original
	qualified type and pass it to c_build_qualified_type.
	* c-typeck.c (c_build_qualified_type): Add arguments
	orig_qual_type and orig_qual_indirect.

gcc/c-family:
	PR c/68162
	* c-common.h (c_build_qualified_type): Add extra default
	arguments.

gcc/cp:
	PR c/68162
	* tree.c (c_build_qualified_type): Add extra arguments.

gcc/testsuite:
	PR c/68162
	* gcc.dg/pr68162-1.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@231194 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 2 insertions, 1 deletions

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index d2db31a628a..5dad0a77d41 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -995,7 +995,8 @@ move (tree expr)
    the C version of this function does not properly maintain canonical
    types (which are not used in C).  */
 tree
-c_build_qualified_type (tree type, int type_quals)
+c_build_qualified_type (tree type, int type_quals, tree /* orig_qual_type */,
+			size_t /* orig_qual_indirect */)
 {
   return cp_build_qualified_type (type, type_quals);
 }