Hello, Igor!
Thanks for your comments!
 
Here is the new commit message:
=========================================================
gdb: support LJ_DUALNUM mode
 
luajit-gdb.py displays integers in LJ_DUALNUM mode as nan-s. The
dumper function produces output considering any input value as a
double. However, in LJ_DUALNUM mode, integers and doubles are stored
differently, so the `itype` of a double must be less than
`LJ_TISNUM`, and the `itype` of an integer must be `LJ_TISNUM`. With
this fact in mind, we can easily differentiate one from another.
 
Closes tarantool/tarantool#6224
=========================================================
 
Here is the diff:
=========================================================
diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
index 9ccca66a..25428745 100644
--- a/src/luajit-gdb.py
+++ b/src/luajit-gdb.py
@@ -507,10 +507,14 @@ pointers respectively.
     '''
     def invoke(self, arg, from_tty):
-        gdb.write('LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}\n'.format(
-            LJ_64 = LJ_64,
-            LJ_GC64 = LJ_GC64
-        ))
+        gdb.write(
+            'LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}, LJ_DUALNUM : {LJ_DUALNUM}\n'
+            .format(
+                LJ_64 = LJ_64,
+                LJ_GC64 = LJ_GC64,
+                LJ_DUALNUM = LJ_DUALNUM
+            )
+        )
 class LJDumpTValue(LJBase):
     '''
@@ -690,7 +694,7 @@ The command requires no args and dumps current GC stats:
         ))
 def init(commands):
-    global LJ_64, LJ_GC64, LJ_DUALNUM, LJ_TISNUM, LJ_FR2, PADDING
+    global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, LJ_TISNUM, PADDING
     # XXX Fragile: though connecting the callback looks like a crap but it
     # respects both Python 2 and Python 3 (see #4828).
@@ -731,7 +735,7 @@ def init(commands):
     try:
         LJ_64 = str(gdb.parse_and_eval('IRT_PTR')) == 'IRT_P64'
         LJ_FR2 = LJ_GC64 = str(gdb.parse_and_eval('IRT_PGC')) == 'IRT_P64'
-        LJ_DUALNUM = lookup('lj_lib_checknumber') is not None
+        LJ_DUALNUM = gdb.lookup_global_symbol('lj_lib_checknumber') is not None
     except:
         gdb.write('luajit-gdb.py failed to load: '
                   'no debugging symbols found for libluajit\n')
=========================================================
 
> 
>>Max,
>>
>>Thanks for the patch! Please consider the comments below.
><snipped>
>>> def tvislightud(o):
>>> if LJ_64 and not LJ_GC64:
>>> @@ -343,7 +346,10 @@ def dump_lj_tudata(tv):
>>> return 'userdata @ {}'.format(strx64(gcval(tv['gcr'])))
>>>
>>> def dump_lj_tnumx(tv):
>>> - return 'number {}'.format(cast('double', tv['n']))
>>> + if tvisint(tv):
>>> + return 'number {}'.format(cast('int32_t', tv['i']))
>>
>>Side note: Agree with Sergey here. It is more convenient to understand
>>that TValue structure for integer slot differs from double.
>I have already fixed the output format here with the fix for v2 of the patch.
><snipped>
> 
>Best regards,
>Maxim Kokryashkin
>