[PATCH 16/16] libctf: support encodings for enums

[Nick Alcock]

The previous commit started to error-check the lookup of
ctf_type_encoding for the underlying type that is internally done when
carrying out a ctf_type_encoding on a slice.

Unfortunately, enums have no encoding, so this has historically been
returning an error (which is ignored) and then populating the cte_format
with uninitialized data.  Now the error is not ignored, this is
returning an error, which breaks linking of CTF containing bitfields of
enumerated type.

CTF format v3 does not record the actual underlying type of a enum, but
we can mock up something that is not *too* wrong, and that is at any
rate better than uninitialized data.

ld/ChangeLog
2021-03-05  Nick Alcock  <nick.alcock@oracle.com>

	* testsuite/ld-ctf/slice.c: Check slices of enums too.
	* testsuite/ld-ctf/slice.d: Results adjusted.

libctf/ChangeLog
2021-03-05  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-types.c (ctf_type_encoding): Support, after a fashion, for enums.
	* ctf-dump.c (ctf_dump_format_type): Do not report enums' degenerate
	encoding.
---
 ld/testsuite/ld-ctf/slice.c | 3 +++
 ld/testsuite/ld-ctf/slice.d | 4 ++--
 libctf/ctf-dump.c           | 5 ++++-
 libctf/ctf-types.c          | 8 +++++++-
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/ld/testsuite/ld-ctf/slice.c b/ld/testsuite/ld-ctf/slice.c
index 7937bcf796e..fb38852142e 100644
--- a/ld/testsuite/ld-ctf/slice.c
+++ b/ld/testsuite/ld-ctf/slice.c
@@ -1,6 +1,9 @@
+enum foo { FOO_BAR };
+
 struct slices {
   int one : 1;
   int two : 2;
   int six : 6;
   int ten :10;
+  enum foo bar:1;
 } slices; 
diff --git a/ld/testsuite/ld-ctf/slice.d b/ld/testsuite/ld-ctf/slice.d
index d1167828f47..72a7074f9ef 100644
--- a/ld/testsuite/ld-ctf/slice.d
+++ b/ld/testsuite/ld-ctf/slice.d
@@ -15,7 +15,7 @@ Contents of CTF section .ctf:
     Compilation unit name: .*slice.c
 #...
     Data object section:	.* \(0x4 bytes\)
-    Type section:	.* \(0x9c bytes\)
+    Type section:	.* \(0xd0 bytes\)
     String section:	.*
 #...
   Data objects:
@@ -28,5 +28,5 @@ Contents of CTF section .ctf:
         *\[0x1\] two: ID 0x[0-9a-f]*: \(kind 1\) int:2 \[slice 0x1:0x2\] \(format 0x1\) \(size 0x1\) \(aligned at 0x1\)
         *\[0x3\] six: ID 0x[0-9a-f]*: \(kind 1\) int:6 \[slice 0x3:0x6\] \(format 0x1\) \(size 0x1\) \(aligned at 0x1\)
         *\[0x9\] ten: ID 0x[0-9a-f]*: \(kind 1\) int:10 \[slice 0x9:0xa\] \(format 0x1\) \(size 0x2\) \(aligned at 0x2\)
-
+        *\[0x13\] bar: ID 0x[0-9a-f]*: \(kind 8\) enum foo:1 \[slice 0x13:0x1\] \(format 0x1\) \(size 0x1\) \(aligned at 0x1\)
 #...
diff --git a/libctf/ctf-dump.c b/libctf/ctf-dump.c
index 409626a224b..8540212eadd 100644
--- a/libctf/ctf-dump.c
+++ b/libctf/ctf-dump.c
@@ -142,7 +142,10 @@ ctf_dump_format_type (ctf_dict_t *fp, ctf_id_t id, int flag)
       unsliced_kind = ctf_type_kind_unsliced (fp, id);
       kind = ctf_type_kind (fp, id);
 
-      if (ctf_type_encoding (fp, id, &ep) == 0)
+      /* Report encodings of everything with an encoding other than enums:
+	 base-type enums cannot have a nonzero cte_offset or cte_bits value.
+	 (Slices of them can, but they are of kind CTF_K_SLICE.)  */
+      if (unsliced_kind != CTF_K_ENUM && ctf_type_encoding (fp, id, &ep) == 0)
 	{
 	  if ((ssize_t) ep.cte_bits != ctf_type_size (fp, id) * CHAR_BIT
 	      && flag & CTF_FT_BITFIELD)
diff --git a/libctf/ctf-types.c b/libctf/ctf-types.c
index ed76eca8463..9afe06ba112 100644
--- a/libctf/ctf-types.c
+++ b/libctf/ctf-types.c
@@ -1157,7 +1157,7 @@ ctf_type_pointer (ctf_dict_t *fp, ctf_id_t type)
   return (ctf_set_errno (ofp, ECTF_NOTYPE));
 }
 
-/* Return the encoding for the specified INTEGER or FLOAT.  */
+/* Return the encoding for the specified INTEGER, FLOAT, or ENUM.  */
 
 int
 ctf_type_encoding (ctf_dict_t *fp, ctf_id_t type, ctf_encoding_t *ep)
@@ -1194,6 +1194,12 @@ ctf_type_encoding (ctf_dict_t *fp, ctf_id_t type, ctf_encoding_t *ep)
       ep->cte_offset = CTF_FP_OFFSET (data);
       ep->cte_bits = CTF_FP_BITS (data);
       break;
+    case CTF_K_ENUM:
+      /* v3 only: we must guess at the underlying integral format.  */
+      ep->cte_format = CTF_INT_SIGNED;
+      ep->cte_offset = 0;
+      ep->cte_bits = 0;
+      break;
     case CTF_K_SLICE:
       {
 	const ctf_slice_t *slice;
-- 
2.30.0.252.gc27e85e57d