libctf: make ctf_dump not crash on OOM

ctf_dump calls ctf_str_append extensively but never checks to see if it
returns NULL (on OOM).  If it ever does, we truncate the string we are
appending to and leak it!

Instead, create a variant of ctf_str_append that returns the *original
string* on OOM, and use it in ctf-dump.  It is far better to omit a tiny
piece of a dump on OOM than to omit a bigger piece, and it is also
better to do this in what is after all purely debugging code than it is
to uglify ctf-dump.c with huge numbers of checks for the out-of-memory
case.  Slightly truncated debugging output is better than no debugging
output at all and an out-of-memory message.

New in v4.

libctf/
	* ctf-impl.h (ctf_str_append_noerr): Declare.
	* ctf-util.c (ctf_str_append_noerr): Define in terms of
	ctf_str_append.
	* ctf-dump.c (str_append): New, call it.
	(ctf_dump_format_type): Use str_append, not ctf_str_append.
	(ctf_dump_label): Likewise.
	(ctf_dump_objts): Likewise.
	(ctf_dump_funcs): Likewise.
	(ctf_dump_var): Likewise.
	(ctf_dump_member): Likewise.
	(ctf_dump_type): Likewise.
	(ctf_dump): Likewise.

1 files changed, 1 insertions, 0 deletions

diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h
index bed34876..6040457 100644
--- a/libctf/ctf-impl.h
+++ b/libctf/ctf-impl.h
@@ -457,6 +457,7 @@ extern ssize_t ctf_pread (int fd, void *buf, ssize_t count, off_t offset);
 
 extern void *ctf_realloc (ctf_file_t *, void *, size_t);
 extern char *ctf_str_append (char *, const char *);
+extern char *ctf_str_append_noerr (char *, const char *);
 extern const char *ctf_strerror (int);
 
 extern ctf_id_t ctf_type_resolve_unsliced (ctf_file_t *, ctf_id_t);