Constify command_line_input

This changes command_line_input to return a "const char *", which is
appropriate because the memory is owned by command_line_input.  Then
it fixes up the users.

I looked at making command_line_input transfer ownership to its caller
instead, but this is complicated due to the way read_next_line is
called, so I decided against it.

Tested by rebuilding.

gdb/ChangeLog
2019-11-08  Tom Tromey  <tromey@adacore.com>

	* top.c (read_command_file): Update.
	(command_line_input): Make return type const.
	* python/py-gdb-readline.c: Update.
	* linespec.c (decode_line_2): Update.
	* defs.h (command_line_input): Make return type const.
	* cli/cli-script.c (read_next_line): Make return type const.
	* ada-lang.c (get_selections): Update.

Change-Id: I27e6c9477fd1005ab5b16e0d337e4c015b6e6248

1 files changed, 2 insertions, 2 deletions

diff --git a/gdb/top.c b/gdb/top.c
index a443159..08c7425 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -420,7 +420,7 @@ read_command_file (FILE *stream)
 
   while (ui->instream != NULL && !feof (ui->instream))
     {
-      char *command;
+      const char *command;
 
       /* Get a command-line.  This calls the readline package.  */
       command = command_line_input (NULL, NULL);
@@ -1210,7 +1210,7 @@ gdb_safe_append_history (void)
    This routine either uses fancy command line editing or simple input
    as the user has requested.  */
 
-char *
+const char *
 command_line_input (const char *prompt_arg, const char *annotation_suffix)
 {
   static struct buffer cmd_line_buffer;