[FYI] Use xstrdup in tui_set_source_content

[Tom Tromey]

valgrind pointed out that the string copy in tui_set_source_content
was not allocating space for the trailing \0:

==3941== Invalid write of size 1
==3941==    at 0x4C3239F: strcpy (vg_replace_strmem.c:512)
==3941==    by 0x72036B: strcpy (string_fortified.h:90)
==3941==    by 0x72036B: tui_set_source_content(symtab*, int, int) (tui-source.c:203)

Looking closer, I don't think there's a need to check the line width
here, so this patch changes it to use xstrdup.

Tested by re-running the TUI under valgrind.  There are still other
valgrind reports from TUI code, but this one is gone.

gdb/ChangeLog
2019-01-02  Tom Tromey  <tom@tromey.com>

	* tui/tui-source.c (tui_set_source_content): Use xstrdup.
---
 gdb/ChangeLog        | 4 ++++
 gdb/tui/tui-source.c | 8 +-------
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c
index 9c2a982cc0..ed9562a930 100644
--- a/gdb/tui/tui-source.c
+++ b/gdb/tui/tui-source.c
@@ -194,15 +194,9 @@ tui_set_source_content (struct symtab *s,
 
 		  xfree (TUI_SRC_WIN->generic.content[cur_line]
 			 ->which_element.source.line);
-		  int alloc_len = text.size ();
-		  if (alloc_len < line_width)
-		    alloc_len = line_width + 1;
 		  TUI_SRC_WIN->generic.content[cur_line]
 		    ->which_element.source.line
-		    = (char *) xmalloc (alloc_len);
-		  strcpy (TUI_SRC_WIN->generic.content[cur_line]
-			  ->which_element.source.line,
-			  text.c_str ());
+		    = xstrdup (text.c_str ());
 
 		  cur_line++;
 		  cur_line_no++;
-- 
2.17.2