Use std::string in ui_out_table

Use std::string for the id field of the ui_out_table object.

I found that all users of ui_out_table_begin passed a non-NULL value to
the tblid parameter, so we don't have to worry about the NULL case.  I
changed the tblid parameter to be a std::string while at it.

gdb/ChangeLog:

	* ui-out.c (struct ui_out_table) <id>: Change type to
	std::string.
	(ui_out_table_begin): Change tblid parameter type to
	std::string, adapt code.
	update following type change.
	(clear_table): Update.
	(ui_out_new): Update.

2 files changed, 17 insertions, 11 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e8d03bf..6d535c5 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,15 @@
 2016-11-30  Simon Marchi  <simon.marchi@polymtl.ca>
 
+	* ui-out.c (struct ui_out_table) <id>: Change type to
+	std::string.
+	(ui_out_table_begin): Change tblid parameter type to
+	std::string, adapt code.
+	update following type change.
+	(clear_table): Update.
+	(ui_out_new): Update.
+
+2016-11-30  Simon Marchi  <simon.marchi@polymtl.ca>
+
 	* cli-out.h (cli_ui_out_data) <streams>: Change type to
 	std::vector.
 	* cli-out.c: Remove vec.h include.
diff --git a/gdb/ui-out.c b/gdb/ui-out.c
index 1713183..a40ac0a 100644
--- a/gdb/ui-out.c
+++ b/gdb/ui-out.c
@@ -27,6 +27,7 @@
 
 #include <vector>
 #include <memory>
+#include <string>
 
 /* table header structures */
 
@@ -72,7 +73,7 @@ struct ui_out_table
 
   /* String identifying the table (as specified in the table_begin
      call).  */
-  char *id;
+  std::string id;
 
   /* Points to the first table header (if any).  */
   struct ui_out_hdr *header_first;
@@ -194,8 +195,7 @@ static void verify_field (struct ui_out *uiout, int *fldno, int *width,
 
 static void
 ui_out_table_begin (struct ui_out *uiout, int nbrofcols,
-		    int nr_rows,
-		    const char *tblid)
+		    int nr_rows, const std::string &tblid)
 {
   if (uiout->table.flag)
     internal_error (__FILE__, __LINE__,
@@ -206,13 +206,11 @@ previous table_end."));
   uiout->table.body_flag = 0;
   uiout->table.entry_level = uiout->level + 1;
   uiout->table.columns = nbrofcols;
-  if (tblid != NULL)
-    uiout->table.id = xstrdup (tblid);
-  else
-    uiout->table.id = NULL;
+  uiout->table.id = tblid;
+
   clear_header_list (uiout);
 
-  uo_table_begin (uiout, nbrofcols, nr_rows, uiout->table.id);
+  uo_table_begin (uiout, nbrofcols, nr_rows, uiout->table.id.c_str ());
 }
 
 void
@@ -577,8 +575,7 @@ uo_table_header (struct ui_out *uiout, int width, enum ui_align align,
 static void
 clear_table (struct ui_out *uiout)
 {
-  xfree (uiout->table.id);
-  uiout->table.id = NULL;
+  uiout->table.id.clear ();
   clear_header_list (uiout);
 }
 
@@ -875,7 +872,6 @@ ui_out_new (const struct ui_out_impl *impl, void *data,
   current->field_count = 0;
   uiout->levels.push_back (std::move (current));
 
-  uiout->table.id = NULL;
   uiout->table.header_first = NULL;
   uiout->table.header_last = NULL;
   uiout->table.header_next = NULL;