gdb: make macro_expand_next return a gdb::unique_xmalloc_ptr<char>

For some reason, macro_expand_next does not return a
gdb::unique_xmalloc_ptr<char>, like its counterparts macro_expand and
macro_expand_once.  This patch fixes that.

macro_buffer::release now returns a gdb::unique_xmalloc_ptr<char> too,
which required updating the other callers.  The `.release (). release
()` in macro_stringify looks a bit funny, but it's because one release
is for the macro_buffer, and the other is for the unique ptr.

I removed the ATTRIBUTE_UNUSED_RESULT on macro_buffer::release, I don't
really understand why it's there.  I don't see how this method could be
called without using the result, that would be an obvious memory leak.
The commit that introduced it (4e4a8b932b7 "Add ATTRIBUTE_UNUSED_RESULT
to macro_buffer") doesn't give any details.

gdb/ChangeLog:

	* c-exp.y (scan_macro_expansion): Don't free `expansion`.
	(lex_one_token): Update.
	* macroexp.c (struct macro_buffer) <release>: Return
	gdb::unique_xmalloc_ptr<char>.
	(macro_stringify): Update.
	(macro_expand): Update.
	(macro_expand_next): Return gdb::unique_xmalloc_ptr<char>.
	* macroexp.h (macro_expand_next): Likewise.

Change-Id: I67a74d0d479d2c20cdc82161ead7c54cea034f56

1 files changed, 7 insertions, 11 deletions

diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index 61fa2fe..7fc23c4 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -2551,17 +2551,13 @@ static const struct token ident_tokens[] =
 
 
 static void
-scan_macro_expansion (char *expansion)
+scan_macro_expansion (const char *expansion)
 {
-  const char *copy;
-
   /* We'd better not be trying to push the stack twice.  */
   gdb_assert (! cpstate->macro_original_text);
 
-  /* Copy to the obstack, and then free the intermediate
-     expansion.  */
-  copy = obstack_strdup (&cpstate->expansion_obstack, expansion);
-  xfree (expansion);
+  /* Copy to the obstack.  */
+  const char *copy = obstack_strdup (&cpstate->expansion_obstack, expansion);
 
   /* Save the old lexptr value, so we can return to it when we're done
      parsing the expanded text.  */
@@ -2631,11 +2627,11 @@ lex_one_token (struct parser_state *par_state, bool *is_quoted_name)
   /* Check if this is a macro invocation that we need to expand.  */
   if (! scanning_macro_expansion ())
     {
-      char *expanded = macro_expand_next (&pstate->lexptr,
-					  *expression_macro_scope);
+      gdb::unique_xmalloc_ptr<char> expanded
+	= macro_expand_next (&pstate->lexptr, *expression_macro_scope);
 
-      if (expanded)
-        scan_macro_expansion (expanded);
+      if (expanded != nullptr)
+        scan_macro_expansion (expanded.get ());
     }
 
   pstate->prev_lexptr = pstate->lexptr;