libctf: eliminate dtd_u, part 4: enums

This is the first tricky one, the first complex multi-entry vlen
containing strings.  To handle this in vlen form, we have to handle
pending refs moving around on realloc.

We grow vlen regions using a new ctf_grow_vlen function, and iterate
through the existing enums every time a grow happens, telling the string
machinery the distance between the old and new vlen region and letting
it adjust the pending refs accordingly.  (This avoids traversing all
outstanding refs to find the refs that need adjusting, at the cost of
having to traverse one enum: an obvious major performance win.)

Addition of enums themselves (and also structs/unions later) is a bit
trickier than earlier forms, because the type might be being promoted
from a forward, and forwards have no vlen: so we have to spot that and
create it if needed.

Serialization of enums simplifies down to just telling the string
machinery about the string refs; all the enum type-lookup code loses all
its dynamic member lookup complexity entirely.

A new test is added that iterates over (and gets values of) an enum with
enough members to force a round of vlen growth.

libctf/ChangeLog
2021-03-18  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-impl.h (ctf_dtdef_t) <dtd_vlen_alloc>: New.
	(ctf_str_move_pending): Declare.
	* ctf-string.c (ctf_str_add_ref_internal): Fix error return.
	(ctf_str_move_pending): New.
	* ctf-create.c (ctf_grow_vlen): New.
	(ctf_dtd_delete): Zero out the vlen_alloc after free.  Free the
	vlen later: iterate over it and free enum name refs first.
	(ctf_add_generic): Populate dtd_vlen_alloc from vlen.
	(ctf_add_enum): populate the vlen; do it by hand if promoting
	forwards.
	(ctf_add_enumerator): Set up the vlen rather than the dmd.  Expand
	it as needed, repointing string refs via ctf_str_move_pending. Add
	the enumerand names as pending strings.
	* ctf-serialize.c (ctf_copy_emembers): Remove.
	(ctf_emit_type_sect): Copy the vlen into place and ref the
	strings.
	* ctf-types.c (ctf_enum_next): The dynamic portion now uses
	the same code as the non-dynamic.
	(ctf_enum_name): Likewise.
	(ctf_enum_value): Likewise.
	* testsuite/libctf-lookup/enum-many-ctf.c: New test.
	* testsuite/libctf-lookup/enum-many.lk: New test.

1 files changed, 3 insertions, 0 deletions

diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h
index a319d7f..9a82d95 100644
--- a/libctf/ctf-impl.h
+++ b/libctf/ctf-impl.h
@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <limits.h>
@@ -192,6 +193,7 @@ typedef struct ctf_dtdef
   ctf_list_t dtd_list;		/* List forward/back pointers.  */
   ctf_id_t dtd_type;		/* Type identifier for this definition.  */
   ctf_type_t dtd_data;		/* Type node, including name.  */
+  size_t dtd_vlen_alloc;	/* Total vlen space allocated.  */
   unsigned char *dtd_vlen;	/* Variable-length data for this type.  */
   union
   {
@@ -734,6 +736,7 @@ extern void ctf_str_free_atoms (ctf_dict_t *);
 extern uint32_t ctf_str_add (ctf_dict_t *, const char *);
 extern uint32_t ctf_str_add_ref (ctf_dict_t *, const char *, uint32_t *ref);
 extern uint32_t ctf_str_add_pending (ctf_dict_t *, const char *, uint32_t *);
+extern int ctf_str_move_pending (ctf_dict_t *, uint32_t *, ptrdiff_t);
 extern int ctf_str_add_external (ctf_dict_t *, const char *, uint32_t offset);
 extern void ctf_str_remove_ref (ctf_dict_t *, const char *, uint32_t *ref);
 extern void ctf_str_rollback (ctf_dict_t *, ctf_snapshot_id_t);