[PATCH v2 5/7] Add early startup command file

[Tom Tromey <tom@tromey.com>]

This adds support for a gdb command file to be read early in startup.
Code that wants to save an early setting can register a callback to be
called to write to this file.  This code is not yet used, but will be
in subsequent patches.

2020-06-22  Tom Tromey  <tom@tromey.com>

	* main.c (captured_main_1): Call read_startup_file.
	* cli/cli-setshow.h (write_startup_functions, add_startup_writer)
	(read_startup_file): Declare.
	(write_startup_setting_ftype): New typedef.
	* cli/cli-setshow.c (STARTUP_FILE): New define.
	(write_startup_functions, startup_file_read): New globals.
	(write_startup_file, add_startup_writer, read_startup_file): New
	functions.
---
 gdb/ChangeLog         | 11 +++++++
 gdb/cli/cli-setshow.c | 76 +++++++++++++++++++++++++++++++++++++++++++
 gdb/cli/cli-setshow.h | 21 ++++++++++++
 gdb/main.c            |  5 +++
 4 files changed, 113 insertions(+)

diff --git a/gdb/cli/cli-setshow.c b/gdb/cli/cli-setshow.c
index 19a5565bfe0..32e867160cb 100644
--- a/gdb/cli/cli-setshow.c
+++ b/gdb/cli/cli-setshow.c
@@ -21,6 +21,8 @@
 #include <ctype.h>
 #include "arch-utils.h"
 #include "observable.h"
+#include "gdbsupport/pathstuff.h"
+#include <vector>
 
 #include "ui-out.h"
 
@@ -29,6 +31,80 @@
 #include "cli/cli-setshow.h"
 #include "cli/cli-utils.h"
 
+/* File name for startup style.  */
+
+#define STARTUP_FILE "startup-commands"
+
+/* Callbacks that will be called to write out startup settings.  */
+static std::vector<write_startup_setting_ftype *> write_startup_functions;
+
+/* True after gdb has read the startup file.  */
+static bool startup_file_read;
+
+/* See cli-setshow.h.  */
+
+void
+write_startup_file ()
+{
+  std::string config_dir = get_standard_config_dir ();
+
+  if (config_dir.empty ())
+    {
+      warning (_("Couldn't determine a path for the startup settings."));
+      return;
+    }
+
+  if (!mkdir_recursive (config_dir.c_str ()))
+    {
+      warning (_("Could not make config directory: %s"),
+	       safe_strerror (errno));
+      return;
+    }
+
+  std::string fullname = config_dir + "/" + STARTUP_FILE;
+  stdio_file outfile;
+
+  if (!outfile.open (fullname.c_str (), FOPEN_WT))
+    perror_with_name (fullname.c_str ());
+
+  for (auto &callback : write_startup_functions)
+    callback (&outfile);
+}
+
+/* See cli-setshow.h.  */
+
+void
+add_startup_writer (write_startup_setting_ftype *callback)
+{
+  write_startup_functions.push_back (callback);
+}
+
+/* See cli-setshow.h.  */
+
+void
+read_startup_file ()
+{
+  std::string config_dir = get_standard_config_dir ();
+
+  if (!config_dir.empty ())
+    {
+      std::string filename = config_dir + "/" + STARTUP_FILE;
+      try
+	{
+	  source_script (filename.c_str (), 1);
+	  /* If reading fails, we don't want to write the file -- it
+	     might overwrite something.  So, we set this flag after
+	     reading.  */
+	  startup_file_read = true;
+	}
+      catch (const gdb_exception &)
+	{
+	  /* Ignore errors.  */
+	}
+    }
+}
+
+\f
 /* Return true if the change of command parameter should be notified.  */
 
 static int
diff --git a/gdb/cli/cli-setshow.h b/gdb/cli/cli-setshow.h
index 83e4984ed6c..35e229022ff 100644
--- a/gdb/cli/cli-setshow.h
+++ b/gdb/cli/cli-setshow.h
@@ -62,4 +62,25 @@ extern std::string get_setshow_command_value_string (const cmd_list_element *c);
 
 extern void cmd_show_list (struct cmd_list_element *list, int from_tty);
 
+/* Write the file of gdb "set" commands that is read early in the
+   startup sequence.  */
+
+extern void write_startup_file ();
+
+/* The type of a callback function that is used when writing the
+   startup file.  */
+
+class ui_file;
+typedef void write_startup_setting_ftype (ui_file *);
+
+/* Add a callback function that will be called when writing the
+   startup sequence.  */
+
+extern void add_startup_writer (write_startup_setting_ftype *callback);
+
+/* Read the startup file.  This should only be called by the gdb
+   startup sequence.  */
+
+extern void read_startup_file ();
+
 #endif /* CLI_CLI_SETSHOW_H */
diff --git a/gdb/main.c b/gdb/main.c
index 3649e4a2201..bd1f6d6b2c5 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -35,6 +35,7 @@
 #include "main.h"
 #include "source.h"
 #include "cli/cli-cmds.h"
+#include "cli/cli-setshow.h"
 #include "objfiles.h"
 #include "auto-load.h"
 #include "maint.h"
@@ -933,6 +934,10 @@ captured_main_1 (struct captured_main_args *context)
   /* Initialize all files.  */
   gdb_init (gdb_program_name);
 
+  /* Set the startup style.  */
+  if (!inhibit_gdbinit && !inhibit_home_gdbinit)
+    read_startup_file ();
+
   /* Now that gdb_init has created the initial inferior, we're in
      position to set args for that inferior.  */
   if (set_args)
-- 
2.17.2