Remove tui_alloc_source_buffer

There is no longer any need for tui_alloc_source_buffer.  The two
callers of this function immediately change the contents of the
window, undoing the work done by this function.

This required adding a move constructor to tui_source_element -- a
mildly surprising find, but without this, resizing the vector will
cause crashes.  This issue was masked earlier because
tui_alloc_source_buffer handled this.

Note that a patch for this bug was submitted here:

    https://sourceware.org/ml/gdb-patches/2019-08/msg00094.html

That patch is better, IMO, but the author as yet hasn't responded to a
request for a ChangeLog entry.

gdb/ChangeLog
2019-08-15  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.h (tui_alloc_source_buffer): Don't declare.
	(struct tui_source_element): Add DISABLE_COPY_AND_ASSIGN, and move
	constructor.
	* tui/tui-winsource.c (tui_alloc_source_buffer): Remove.
	* tui/tui-source.c (tui_set_source_content): Update.
	* tui/tui-disasm.c (tui_set_disassem_content): Update.

4 files changed, 11 insertions, 26 deletions

diff --git a/gdb/tui/tui-disasm.c b/gdb/tui/tui-disasm.c
index e55f35d..2394394 100644
--- a/gdb/tui/tui-disasm.c
+++ b/gdb/tui/tui-disasm.c
@@ -179,8 +179,6 @@ tui_set_disassem_content (tui_source_window_base *win_info,
   if (pc == 0)
     return TUI_FAILURE;
 
-  tui_alloc_source_buffer (win_info);
-
   win_info->gdbarch = gdbarch;
   win_info->start_line_or_addr.loa = LOA_ADDRESS;
   win_info->start_line_or_addr.u.addr = pc;
diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c
index 7c173f8..3d88f66 100644
--- a/gdb/tui/tui-source.c
+++ b/gdb/tui/tui-source.c
@@ -135,7 +135,6 @@ tui_set_source_content (tui_source_window_base *win_info,
       int line_width, nlines;
 
       ret = TUI_SUCCESS;
-      tui_alloc_source_buffer (win_info);
       line_width = win_info->width - 1;
       /* Take hilite (window border) into account, when
 	 calculating the number of lines.  */
diff --git a/gdb/tui/tui-winsource.c b/gdb/tui/tui-winsource.c
index a852696..121f19a 100644
--- a/gdb/tui/tui-winsource.c
+++ b/gdb/tui/tui-winsource.c
@@ -620,23 +620,3 @@ tui_source_window_base::update_exec_info ()
     }
   execution_info->refresh_window ();
 }
-
-
-void
-tui_alloc_source_buffer (struct tui_source_window_base *win_info)
-{
-  int i, line_width, max_lines;
-
-  /* The window width/height includes the highlight box.  Determine actual
-     content dimensions, including string null-terminators.  */
-  max_lines = win_info->height - 2;
-  line_width = win_info->width - 2 + 1;
-
-  /* Allocate the buffer for the source lines.  */
-  win_info->content.resize (max_lines);
-  for (i = 0; i < max_lines; i++)
-    {
-      if (win_info->content[i].line == nullptr)
-	win_info->content[i].line = (char *) xmalloc (line_width);
-    }
-}
diff --git a/gdb/tui/tui-winsource.h b/gdb/tui/tui-winsource.h
index 237c4da..bff2560 100644
--- a/gdb/tui/tui-winsource.h
+++ b/gdb/tui/tui-winsource.h
@@ -69,6 +69,17 @@ struct tui_source_element
     xfree (line);
   }
 
+  DISABLE_COPY_AND_ASSIGN (tui_source_element);
+
+  tui_source_element (tui_source_element &&other)
+    : line (other.line),
+      line_or_addr (other.line_or_addr),
+      is_exec_point (other.is_exec_point),
+      break_mode (other.break_mode)
+  {
+    other.line = nullptr;
+  }
+
   char *line = nullptr;
   struct tui_line_or_address line_or_addr;
   bool is_exec_point = false;
@@ -173,9 +184,6 @@ extern void tui_update_source_windows_with_line (struct symtab *,
 extern void tui_clear_source_content (struct tui_source_window_base *);
 extern void tui_erase_source_content (struct tui_source_window_base *);
 
-extern void tui_alloc_source_buffer (struct tui_source_window_base *);
-
-
 /* Constant definitions. */
 #define SCROLL_THRESHOLD 2	/* Threshold for lazy scroll.  */