Re: GDB version as convenience variable

[Eli Zaretskii <eliz@gnu.org>]

Seems like there's a consensus to have 2 separate variables, so here's
a version of the patch that does that.  OK to commit?

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 2de1adc..f841e0a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2019-03-06  Eli Zaretskii  <eliz@gnu.org>
+
+	* NEWS: Announce $_gdb_major and $_gdb_minor.
+
+	* top.c (init_gdb_version_vars): New function.
+	(gdb_init): Call init_gdb_version_vars.
+
 2019-03-25  Alan Hayward  <alan.hayward@arm.com>
 
 	* s390-linux-nat.c: Add include.
diff --git a/gdb/NEWS b/gdb/NEWS
index c45b313..676f0a0 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,12 @@
 
 *** Changes since GDB 8.3
 
+* New built-in convenience variables $_gdb_major and $_gdb_minor
+  provide the GDB version.  They are handy for conditionally using
+  features available only in or since specific GDB versions, in
+  scripts that should work error-free with many different versions,
+  such as in system-wide init files.
+
 *** Changes in GDB 8.3
 
 * GDB and GDBserver now support access to additional registers on
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 1f41498..c384267 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,7 @@
+2019-03-06  Eli Zaretskii  <eliz@gnu.org>
+
+	* gdb.texinfo (Convenience Vars): Document $_gdb_version.
+
 2019-03-22  Alan Hayward  <alan.hayward@arm.com>
 	    Jiong Wang  <jiong.wang@arm.com>
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4c1d5e8..115bcf7 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -11211,6 +11211,17 @@
 @item $_gthread
 The global number of the current thread.  @xref{global thread numbers}.
 
+@item $_gdb_major
+@itemx $_gdb_minor
+@vindex $_gdb_major@{, convenience variable}
+@vindex $_gdb_minor@{, convenience variable}
+The major and minor version numbers of the running @value{GDBN}.
+Development snapshots and pretest versions have their minor version
+incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
+the value 12 for @code{$_gdb_minor}.  These variables allow you to
+write scripts that work with different versions of @value{GDBN}
+without errors caused by features unavailable in some of those
+versions.
 @end table
 
 @node Convenience Funs
diff --git a/gdb/top.c b/gdb/top.c
index b10b064..afb77c0 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -2003,6 +2004,17 @@ set_history_filename (const char *args,
 }
 
 static void
+init_gdb_version_vars (void)
+{
+  struct internalvar *major_version_var = create_internalvar ("_gdb_major");
+  struct internalvar *minor_version_var = create_internalvar ("_gdb_minor");
+  int vmajor = 0, vminor = 0, vrevision = 0;
+  sscanf (version, "%d.%d.%d", &vmajor, &vminor, &vrevision);
+  set_internalvar_integer (major_version_var, vmajor);
+  set_internalvar_integer (minor_version_var, vminor + (vrevision > 0));
+}
+
+static void
 init_main (void)
 {
   struct cmd_list_element *c;
@@ -2206,4 +2218,7 @@ gdb_init (char *argv0)
      prefix to be installed.  Keep things simple and just do final
      script initialization here.  */
   finish_ext_lang_initialization ();
+
+  /* Create $_gdb_major and $_gdb_minor convenience variables.  */
+  init_gdb_version_vars ();
 }