[Swig-devel] [ swig-Bugs-2485751 ] Tcl wrong int64 parameter

[SourceForge.net <no...@so...>]

Bugs item #2485751, was opened at 2009-01-04 09:59
Message generated for change (Comment added) made by pdokj
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101645&aid=2485751&group_id=1645

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: tcl
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Vera (vera_soft)
Assigned to: Nobody/Anonymous (nobody)
Summary: Tcl wrong int64 parameter

Initial Comment:
I wrote a C function, expecting "long long" as parameter:
int c_my (long long big_offset);

With SWIG I have an interface to Tcl.

In Tcl I call:
c_my 3000000000

in C (c_my) I got:
big_offset = -1294967296.

There is an bug in SWIG_AsVal_long_SS_long.

The whole discussion is in comp.lang.tcl
Subj:"64 bit integers (long long)"


Here is my (working) hotfix. Replace all the code in SWIG_AsVal_long_SS_long with:

SWIGINTERN int
SWIG_AsVal_long_SS_long SWIG_TCL_DECL_ARGS_2(Tcl_Obj *obj, long long *val)
{
    if (Tcl_GetWideIntFromObj(0, obj, val) != TCL_OK) {
        return SWIG_TypeError;
    }
    return SWIG_OK;
}


----------------------------------------------------------------------

Comment By: Kjell Wooding (pdokj)
Date: 2010-12-01 12:39

Message:
--- tclprimtypes.swg.orig       2010-12-01 12:11:23.000000000 -0700
+++ tclprimtypes.swg    2010-12-01 12:30:40.000000000 -0700
@@ -133,11 +133,11 @@
 SWIGINTERN int
 SWIG_AsVal_dec(long long)(Tcl_Obj *obj, long long *val)
 {
-  long v;
-  if (Tcl_GetLongFromObj(0,obj, &v) == TCL_OK) {
-    if (val) *val = v;
-    return SWIG_OK;
-  } else {
+    /*
+     * XXX Bug - remove incorrect optimization.
+     * Optimized fix needs GetWideIntFromObj (tcl >=8.4), so
+     * just remove it for now
+     */
     int len = 0;
     const char *nptr = Tcl_GetStringFromObj(obj, &len);
     if (nptr && len > 0) {
@@ -157,7 +157,6 @@
        }
       }
     }
-  }
   return SWIG_TypeError;
 }
 }


----------------------------------------------------------------------

Comment By: Kjell Wooding (pdokj)
Date: 2010-12-01 12:38

Message:
This is still a bug in 2.0.1. 
The problem is in tclprimtypes.swg:

    SWIGINTERN int
    SWIG_AsVal_dec(long long)(Tcl_Obj *obj, long long *val)
    {
      long v;
      if (Tcl_GetLongFromObj(0,obj, &v) == TCL_OK) {
        if (val) *val = v;
        return SWIG_OK;
      } else {
    ...

When trying to convert a signed int64 (long long), this code attempts to
convert first to a signed int32 (long). If the input is positive, but
between 2^31 and 2^32, the conversion attempt will appear to succeed (at
least, with the supplied test), but will cast the result to a negative
quantity)

The solution is to not do this silly optimization at all, or to require
Tcl >=8.4, and change this call to Tcl_GetWideIntFromObj

Patch attached. Please fix this, as spending a day chasing a bug that was
identified back in 2009 is no kind of fun.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101645&aid=2485751&group_id=1645