segfault on opening a register window

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segfault on opening a register window

Atsushi Nemoto
The insight crashes with segfault when opening a register window after
connecting to a remote ARM target.  I confirmed the problem with 7.0.1,
7.1 and current CVS.

The crash happened here:

Program received signal SIGSEGV, Segmentation fault.
get_register (regnum=0, arg={integer = 0, ptr = 0x0})
    at ../../insight/src/gdb/gdbtk/generic/gdbtk-register.c:341
341      if ((TYPE_CODE (reg_vtype) == TYPE_CODE_UNION)

(gdb) p reg_vtype
$1 = (struct type *) 0x66

The reg_vtype pointer had a wrong value.  I realized that contents of
regtype[] array are corrupted.  This is because current gdbarch was
changed but regformat or regtype array was not reconstructed.

1. start insight.
2. setup_architecture_data() was called.
3. connecting to a remote target, then gdbarch (also numregs) changed.
4. gdb_regformat() was called and write to outside of allocated
   regformat, regtype array.

The problem is setup_architecture_data() is not called when gdbarch
was changed.  If I opened the register window _before_ connecting to
a remote target, setup_architecture_data() is called via
gdb_reg_arch_changed.  But it seems gdb_reg_arch_changed is called
only if the register windows was opened.

Here is a quick workaround.  Is there good way to call
setup_architecture_data() automatically if current arch was changed?
Or other good fix?


--- gdb/gdbtk/generic/gdbtk-register.c.org 2010-09-07 23:06:48.000000000 +0900
+++ gdb/gdbtk/generic/gdbtk-register.c 2010-09-07 23:06:59.000000000 +0900
@@ -65,6 +65,7 @@ static void get_register_types (int regn
 static char *old_regs = NULL;
 static int *regformat = (int *)NULL;
 static struct type **regtype = (struct type **)NULL;
+static struct gdbarch *cur_gdbarch = NULL;
 
 int
 Gdbtk_Register_Init (Tcl_Interp *interp)
@@ -149,6 +150,10 @@ gdb_register_info (ClientData clientData
       return TCL_ERROR;
     }
   
+  /* Check gdbarch change to avoid corruption of regformat/regtype array */
+  if (cur_gdbarch != get_current_arch ())
+    setup_architecture_data ();
+
   /* Skip the option */
   objc -= 2;
   objv += 2;
@@ -469,6 +474,7 @@ setup_architecture_data ()
 {
   int numregs;
 
+  cur_gdbarch = get_current_arch ();
   xfree (old_regs);
   xfree (regformat);
   xfree (regtype);

---
Atsushi Nemoto