libctf: lookup_by_name: do not return success for nonexistent pointer types

The recent work allowing lookups of pointers in child dicts when the
pointed-to type is in the parent dict broke the case where a pointer
type that does not exist at all is looked up: we mistakenly return the
pointed-to type, which is likely not a pointer at all.  This causes
considerable confusion.

Fixed, with a new testcase.

libctf/ChangeLog
2021-01-19  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-lookup.c (ctf_lookup_by_name_internal): Do not return the
	base type if looking up a nonexistent pointer type.
	* testsuite/libctf-regression/pptrtab*: Test it.

3 files changed, 13 insertions, 2 deletions

diff --git a/libctf/testsuite/libctf-regression/pptrtab-a.c b/libctf/testsuite/libctf-regression/pptrtab-a.c
index e9f656a0bc8..65414877114 100644
--- a/libctf/testsuite/libctf-regression/pptrtab-a.c
+++ b/libctf/testsuite/libctf-regression/pptrtab-a.c
@@ -1,3 +1,5 @@
 typedef long a_t;
+typedef long b_t;
 
 a_t *a;
+b_t ignore2;
diff --git a/libctf/testsuite/libctf-regression/pptrtab-b.c b/libctf/testsuite/libctf-regression/pptrtab-b.c
index 6142f194c19..e458021efb1 100644
--- a/libctf/testsuite/libctf-regression/pptrtab-b.c
+++ b/libctf/testsuite/libctf-regression/pptrtab-b.c
@@ -1,4 +1,5 @@
 typedef long a_t;
+typedef long b_t;
 
 a_t b;
-
+b_t ignore1;
diff --git a/libctf/testsuite/libctf-regression/pptrtab.c b/libctf/testsuite/libctf-regression/pptrtab.c
index 5d3c2f2ee93..fe1b8fe2b43 100644
--- a/libctf/testsuite/libctf-regression/pptrtab.c
+++ b/libctf/testsuite/libctf-regression/pptrtab.c
@@ -23,13 +23,18 @@ main (int argc, char *argv[])
     goto open_err;
 
   /* Make sure we can look up a_t * by name in all non-parent dicts, even though
-     the a_t * and the type it points to are in distinct dicts.  */
+     the a_t * and the type it points to are in distinct dicts; make sure we
+     cannot look up b_t *.  */
 
   while ((fp = ctf_archive_next (ctf, &i, &arcname, 1, &err)) != NULL)
     {
       if ((type = ctf_lookup_by_name (fp, "a_t *")) == CTF_ERR)
 	goto err;
 
+      if ((ctf_lookup_by_name (fp, "b_t *")) != CTF_ERR ||
+          ctf_errno (fp) != ECTF_NOTYPE)
+	goto noerr;
+
       if (ctf_type_reference (fp, type) == CTF_ERR)
 	goto err;
 
@@ -51,4 +56,7 @@ main (int argc, char *argv[])
  err:
   fprintf (stderr, "Lookup failed in %s: %s\n", arcname, ctf_errmsg (ctf_errno (fp)));
   return 1;
+ noerr:
+  fprintf (stderr, "Lookup unexpectedly succeeded in %s\n", arcname);
+  return 1;
 }