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authorAndrew Burgess <andrew.burgess@embecosm.com>2020-01-22 18:21:58 +0000
committerAndrew Burgess <andrew.burgess@embecosm.com>2020-03-02 18:59:38 +0000
commit63e163f24fe80fe1509527e6ccfcfb9622f5e99e (patch)
tree36d85fd9d5a52b110ecfcd4dd5f70fdf4d36304d /gdb/top.c
parent81b86b9702b5be9d022e9b0c96c1ee2ce339b5b9 (diff)
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gdb: Allow GDB to _not_ load a previous command history
This commit aims to give a cleaner mechanism by which the user can prevent GDB from trying to load any previous command history. Currently the user can change the path to the history file, either using a command line flag, or by setting the GDBHISTFILE environment variable, and if the path is set to a non-existent file, then obviously GDB wont load any command history. However, this feels like a bit of a bodge, I'd like to add an official mechanism by which we can disable command history loading. Why would we want to prevent command history loading? The specific use case I have is GDB starting with a CWD that is a network mounted directory, and there is no command history present. Still GDB will access the network in order to check for the file. In my particular use case I'm actually starting a large number of GDB instances in parallel, all in the same network mounted directory, the large number of network accesses looking for this file introduces a noticeable delay at GDB startup. The approach I'm proposing here is a slight adjustment to the current rules for setting up the history filename. Currently, if a user does this, they see an error: (gdb) set history filename Argument required (filename to set it to.). However, if a user does this: $ GDBHISTFILE= gdb --quiet (gdb) set history save on (gdb) q warning: Could not rename -gdb18416~ to : No such file or directory So, we already have a bug in this area. My plan is to allow the empty filename to be accepted, and for this to mean, neither load, nor save the command history. This does mean that we now have two mechanisms to prevent saving the command history: (gdb) set history filename or (gdb) set history save off But the only way to prevent loading the command history is to set the filename to the empty string _before_ you get to a GDB prompt, either using a command line option, or the environment variable. I've updated some of the show commands, for example this session: (gdb) set history filename (gdb) show history filename There is no filename currently set for recording the command history in. (gdb) show history save Saving of the history record on exit is off. (gdb) set history save on (gdb) show history save Saving of the history is disabled due to the value of 'history filename'. (gdb) set history filename /tmp/hist (gdb) show history save Saving of the history record on exit is on. I've updated the manual, and added some tests. gdb/ChangeLog: * NEWS: Mention new behaviour of the history filename. * top.c (write_history_p): Add comment. (show_write_history_p): Add header comment, give a different message when history writing is on, but the history filename is empty. (history_filename): Add comment. (history_filename_empty): New function. (show_history_filename): Add header comment, give a different message when the filename is empty. (init_history): Compare history_filename against nullptr, and only read history if the filename is not empty. (set_history_filename): Add header comment, and only make non-empty filenames absolute. (init_main): Make the filename argument to 'set history filename' optional. gdb/doc/ChangeLog: * gdb.texinfo (Command History): Extend description for GDBHISTFILE and GDBHISTSIZE, add detail about the filename for 'set history filename' being optional. Describe the effect of an empty history filename on 'set history save on'. gdb/testsuite/ChangeLog: * gdb.base/default.exp: Remove test of 'set history filename'. * gdb.base/gdbinit-history.exp: Add tests for setting the history filename to the empty string. * lib/gdb.exp (gdb_init): Unset environment variables GDBHISTFILE and GDBHISTSIZE. Change-Id: Ia586e4311182fac99113b60f11ef8a11fbd5450b
Diffstat (limited to 'gdb/top.c')
-rw-r--r--gdb/top.c51
1 files changed, 41 insertions, 10 deletions
diff --git a/gdb/top.c b/gdb/top.c
index 1a98ae1..e243248 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -84,6 +84,8 @@
extern void initialize_all_files (void);
+static bool history_filename_empty (void);
+
#define PROMPT(X) the_prompts.prompt_stack[the_prompts.top + X].prompt
#define PREFIX(X) the_prompts.prompt_stack[the_prompts.top + X].prefix
#define SUFFIX(X) the_prompts.prompt_stack[the_prompts.top + X].suffix
@@ -884,13 +886,22 @@ static bool command_editing_p;
/* static */ bool history_expansion_p;
+/* Should we write out the command history on exit? In order to write out
+ the history both this flag must be true, and the history_filename
+ variable must be set to something sensible. */
static bool write_history_p;
+
+/* Implement 'show history save'. */
static void
show_write_history_p (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
- fprintf_filtered (file, _("Saving of the history record on exit is %s.\n"),
- value);
+ if (!write_history_p || !history_filename_empty ())
+ fprintf_filtered (file, _("Saving of the history record on exit is %s.\n"),
+ value);
+ else
+ fprintf_filtered (file, _("Saving of the history is disabled due to "
+ "the value of 'history filename'.\n"));
}
/* The variable associated with the "set/show history size"
@@ -919,14 +930,30 @@ show_history_remove_duplicates (struct ui_file *file, int from_tty,
value);
}
+/* The name of the file in which GDB history will be written. If this is
+ set to NULL, of the empty string then history will not be written. */
static char *history_filename;
+
+/* Return true if the history_filename is either NULL or the empty string,
+ indicating that we should not try to read, nor write out the history. */
+static bool
+history_filename_empty (void)
+{
+ return (history_filename == nullptr || *history_filename == '\0');
+}
+
+/* Implement 'show history filename'. */
static void
show_history_filename (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
- fprintf_filtered (file, _("The filename in which to record "
- "the command history is \"%ps\".\n"),
- styled_string (file_name_style.style (), value));
+ if (!history_filename_empty ())
+ fprintf_filtered (file, _("The filename in which to record "
+ "the command history is \"%ps\".\n"),
+ styled_string (file_name_style.style (), value));
+ else
+ fprintf_filtered (file, _("There is no filename currently set for "
+ "recording the command history in.\n"));
}
/* This is like readline(), but it has some gdb-specific behavior.
@@ -2017,9 +2044,9 @@ init_history (void)
set_readline_history_size (history_size_setshow_var);
tmpenv = getenv ("GDBHISTFILE");
- if (tmpenv)
+ if (tmpenv != nullptr)
history_filename = xstrdup (tmpenv);
- else if (!history_filename)
+ else if (history_filename == nullptr)
{
/* We include the current directory so that if the user changes
directories the file written will be the same as the one
@@ -2034,7 +2061,9 @@ init_history (void)
gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (fname));
history_filename = temp.release ();
}
- read_history (history_filename);
+
+ if (!history_filename_empty ())
+ read_history (history_filename);
}
static void
@@ -2103,6 +2132,8 @@ show_gdb_datadir (struct ui_file *file, int from_tty,
gdb_datadir.c_str ()));
}
+/* Implement 'set history filename'. */
+
static void
set_history_filename (const char *args,
int from_tty, struct cmd_list_element *c)
@@ -2110,7 +2141,7 @@ set_history_filename (const char *args,
/* We include the current directory so that if the user changes
directories the file written will be the same as the one
that was read. */
- if (!IS_ABSOLUTE_PATH (history_filename))
+ if (!history_filename_empty () && !IS_ABSOLUTE_PATH (history_filename))
{
gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (history_filename));
@@ -2217,7 +2248,7 @@ By default this option is set to 0."),
show_history_remove_duplicates,
&sethistlist, &showhistlist);
- add_setshow_filename_cmd ("filename", no_class, &history_filename, _("\
+ add_setshow_optional_filename_cmd ("filename", no_class, &history_filename, _("\
Set the filename in which to record the command history."), _("\
Show the filename in which to record the command history."), _("\
(the list of previous commands of which a record is kept)."),