[gdb] Initialize main_thread_id earlier

I wrote a patch using is_main_thread (), and found it returning false in the
main thread due to main_thread_id not being initialized yet.

Initialization currently takes place in _initialize_run_on_main_thread, but
that's too late for earlier uses.

Fix this by initializing, either:
- when entering main, or
- on an earlier first use.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/gdb/gdb.c b/gdb/gdb.c
index 71a3fd1..6e3ff07 100644
--- a/gdb/gdb.c
+++ b/gdb/gdb.c
@@ -19,10 +19,17 @@
 #include "defs.h"
 #include "main.h"
 #include "interps.h"
+#include "run-on-main-thread.h"
 
 int
 main (int argc, char **argv)
 {
+  /* The first call to is_main_thread () should be from the main thread.
+     If this is the first call, then that requirement is fulfilled here.
+     If this is not the first call, then this verifies that the first call
+     fulfilled that requirement.  */
+  gdb_assert (is_main_thread ());
+
   struct captured_main_args args;
 
   memset (&args, 0, sizeof args);