Fix tracepoint.c:parse_tracepoint_definition leak (and one more)

Coverity points out that gdb/tracepoint.c:parse_tracepoint_definition
can leak 'cond' in this line:

      cond = (char *) xmalloc (2 * xlen + 1);

That can leak because we're in a loop and 'cond' may have already been
xmalloc'ed into in a previous iteration.  That won't normally happen,
because we don't expect to see a tracepoint definition with multiple
conditions listed, but, it doesn't hurt to be pedantically correct,
in case some stub manages to send something odd back to GDB.

At first I thought I'd just replace the xmalloc call with:

      cond = (char *) xrealloc (cond, 2 * xlen + 1);

and be done with it.  However, my pedantic self realizes that
warning() can throw as well (due to pagination + Ctrl-C), so I fixed
it using gdb::unique_xmalloc_ptr instead.

While doing this, I noticed that these vectors in struct uploaded_tp:

  std::vector<char *> actions;
  std::vector<char *> step_actions;

hold heap-allocated strings, but nothing is freeing the strings,
AFAICS.

So I ended up switching all the heap-allocated strings in uploaded_tp
to unique pointers.  This patch is the result of that.

I also wrote an alternative, but similar patch that uses std::string
throughout instead of gdb::unique_xmalloc_ptr, but in the end reverted
it because the code didn't look that much better, and I kind of
dislike replacing pointers with fat std::string's (3 or 4 times the
size of a pointer) in structures.

gdb/ChangeLog:
2019-01-10  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (read_uploaded_action)
	(create_tracepoint_from_upload): Adjust to use
	gdb::unique_xmalloc_ptr.
	* ctf.c (ctf_write_uploaded_tp):
	(SET_ARRAY_FIELD): Use emplace_back.
	(SET_STRING_FIELD): Adjust to use gdb::unique_xmalloc_ptr.
	* tracefile-tfile.c (tfile_write_uploaded_tp):
	* tracepoint.c (parse_tracepoint_definition): Adjust to use
	gdb::unique_xmalloc_ptr.
	* tracepoint.h (struct uploaded_tp) <cond, actions, step_actions,
	at_string, cond_string, cmd_strings>: Replace char pointers
	with gdb::unique_xmalloc_ptr.

1 files changed, 11 insertions, 10 deletions

diff --git a/gdb/tracefile-tfile.c b/gdb/tracefile-tfile.c
index afff422..831f162 100644
--- a/gdb/tracefile-tfile.c
+++ b/gdb/tracefile-tfile.c
@@ -262,31 +262,32 @@ tfile_write_uploaded_tp (struct trace_file_writer *self,
     fprintf (writer->fp, ":F%x", utp->orig_size);
   if (utp->cond)
     fprintf (writer->fp,
-	     ":X%x,%s", (unsigned int) strlen (utp->cond) / 2,
-	     utp->cond);
+	     ":X%x,%s", (unsigned int) strlen (utp->cond.get ()) / 2,
+	     utp->cond.get ());
   fprintf (writer->fp, "\n");
-  for (char *act : utp->actions)
+  for (const auto &act : utp->actions)
     fprintf (writer->fp, "tp A%x:%s:%s\n",
-	     utp->number, phex_nz (utp->addr, sizeof (utp->addr)), act);
-  for (char *act : utp->step_actions)
+	     utp->number, phex_nz (utp->addr, sizeof (utp->addr)), act.get ());
+  for (const auto &act : utp->step_actions)
     fprintf (writer->fp, "tp S%x:%s:%s\n",
-	     utp->number, phex_nz (utp->addr, sizeof (utp->addr)), act);
+	     utp->number, phex_nz (utp->addr, sizeof (utp->addr)), act.get ());
   if (utp->at_string)
     {
       encode_source_string (utp->number, utp->addr,
-			    "at", utp->at_string, buf, MAX_TRACE_UPLOAD);
+			    "at", utp->at_string.get (),
+			    buf, MAX_TRACE_UPLOAD);
       fprintf (writer->fp, "tp Z%s\n", buf);
     }
   if (utp->cond_string)
     {
       encode_source_string (utp->number, utp->addr,
-			    "cond", utp->cond_string,
+			    "cond", utp->cond_string.get (),
 			    buf, MAX_TRACE_UPLOAD);
       fprintf (writer->fp, "tp Z%s\n", buf);
     }
-  for (char *act : utp->cmd_strings)
+  for (const auto &act : utp->cmd_strings)
     {
-      encode_source_string (utp->number, utp->addr, "cmd", act,
+      encode_source_string (utp->number, utp->addr, "cmd", act.get (),
 			    buf, MAX_TRACE_UPLOAD);
       fprintf (writer->fp, "tp Z%s\n", buf);
     }