libctf, ld: handle nonrepresentable types better

ctf_type_visit (used, among other things, by the type dumping code) was
aborting when it saw a nonrepresentable type anywhere: even a single
structure member with a nonrepresentable type caused an abort with
ECTF_NONREPRESENTABLE.  This is not useful behaviour, given that the
abort comes from a type-resolution we are only doing in order to
determine whether the type is a structure or union.  We know
nonrepresentable types can't be either, so handle that case and
pass the nonrepresentable type down.

(The added test verifies that the dumper now handles this case and
prints nonrepresentable structure members as it already does
nonrepresentable top-level types, rather than skipping the whole
structure -- or, without the previous commit, skipping the whole types
section.)

ld/ChangeLog
2021-10-25  Nick Alcock  <nick.alcock@oracle.com>

	* testsuite/ld-ctf/nonrepresentable-member.*: New test.

libctf/ChangeLog
2021-10-25  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-types.c (ctf_type_rvisit): Handle nonrepresentable types.

ld/ChangeLog

@@ -1,3 +1,7 @@
+2021-10-25  Nick Alcock  <nick.alcock@oracle.com>
+
+	* testsuite/ld-ctf/nonrepresentable-member.*: New test.
+
 2021-10-25  Nick Alcock  <nick.alcock@oracle.com>
 
 	* testsuite/ld-ctf/array.d: Change --ctf=.ctf to --ctf.

ld/testsuite/ld-ctf/nonrepresentable-member.c

@@ -0,0 +1,7 @@
+struct blah
+{
+  int boring;
+  int __attribute__((vector_size(8))) foo;
+  const int __attribute__((vector_size(8))) bar;
+  int this_is_printed;
+} wibble __attribute__((__used__));

ld/testsuite/ld-ctf/nonrepresentable-member.d

@@ -0,0 +1,25 @@
+#as:
+#source: nonrepresentable-member.c
+#objdump: --ctf
+#ld: -shared
+#name: Nonrepresentable members
+
+.*: +file format .*
+
+Contents of CTF section .ctf:
+
+  Header:
+    Magic number: 0xdff2
+    Version: 4 \(CTF_VERSION_3\)
+#...
+  Types:
+#...
+    0x[0-9a-f]*: \(kind 6\) struct blah .*
+        *\[0x0\] boring: ID 0x[0-9a-f]*: \(kind 1\) int .*
+        *\[0x[0-9a-f]*\] foo: .* \(.*represent.*\)
+        *\[0x[0-9a-f]*\] bar: .* \(.*represent.*\)
+        *\[0x[0-9a-f]*\] this_is_printed: ID 0x[0-9a-f]*: \(kind 1\) int .*
+#...
+
+  Strings:
+#...

libctf/ChangeLog

@@ -1,3 +1,7 @@
+2021-10-25  Nick Alcock  <nick.alcock@oracle.com>
+
+	* ctf-types.c (ctf_type_rvisit): Handle nonrepresentable types.
+
 2021-10-25  Nick Alcock  <nick.alcock@oracle.com>
 
 	* ctf-dump.c (ctf_dump_type): Do not abort on error.

libctf/ctf-types.c

@@ -1641,20 +1641,27 @@ ctf_type_rvisit (ctf_dict_t *fp, ctf_id_t type, ctf_visit_f *func,
   unsigned char *vlen;
   ssize_t size, increment, vbytes;
   uint32_t kind, n, i = 0;
+  int nonrepresentable = 0;
   int rc;
 
-  if ((type = ctf_type_resolve (fp, type)) == CTF_ERR)
-    return -1;			/* errno is set for us.  */
+  if ((type = ctf_type_resolve (fp, type)) == CTF_ERR) {
+    if (ctf_errno (fp) != ECTF_NONREPRESENTABLE)
+      return -1;		/* errno is set for us.  */
+    else
+      nonrepresentable = 1;
+  }
 
-  if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
-    return -1;			/* errno is set for us.  */
+  if (!nonrepresentable)
+    if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
+      return -1;		/* errno is set for us.  */
 
   if ((rc = func (name, otype, offset, depth, arg)) != 0)
     return rc;
 
-  kind = LCTF_INFO_KIND (fp, tp->ctt_info);
+  if (!nonrepresentable)
+    kind = LCTF_INFO_KIND (fp, tp->ctt_info);
 
-  if (kind != CTF_K_STRUCT && kind != CTF_K_UNION)
+  if (nonrepresentable || (kind != CTF_K_STRUCT && kind != CTF_K_UNION))
     return 0;
 
   ctf_get_ctt_size (fp, tp, &size, &increment);