[M3devel] LONGREAL and m3gdb (was gettimeofday called from CheckLoadTracedRef?)

[Rodney M. Bates]

Floating point values in m3gdb is one area I have never done any
work on at all, but I have been aware for a long time that it probably
needs some.  It just uses stock gdb's code, which also just uses
the C builtin arithmetic on C floating types.  At the very least, the
mapping between C's two and Modula-3's three floating types, on
the various targets, is purely an accident right now.  I recall there
is something wrong in the formatting too.

Mika Nystrom wrote:
> Hi Modula-3ers, especially Tony,
>
> I'm seeing the following behavior a lot in a program I'm running:
>
> #0  0x68ecbba7 in gettimeofday () from /lib/libc.so.5
> #1  0x68611cb9 in Now () at ../src/time/POSIX/TimePosix.m3:16
> #2  0x685ecf06 in CollectorOn (timeOnEntry=Invalid C/C++ type code 30 in symbol table.
> ) at ../src/runtime/common/RTCollector.m3:674
> #3  0x685f2476 in CheckLoadTracedRef (ref=Invalid C/C++ type code 46 in symbol table.
> ) at ../src/runtime/common/RTCollector.m3:2271
> #4  0x68139379 in Get (tbl=Invalid C/C++ type code 26 in symbol table.
> )
>     at ../FreeBSD4/SortedTotalOrderLRTbl.m3 => /usr/local/cm3/pkg/libm3/src/sortedtable/SortedTable.mg:145
>
> Is it normal for CheckLoadTracedRef to make system calls?
>
> Hmm, why is it even doing CheckLoadTracedRef?  Here's the code (from SortedTable.mg):
>
>
> PROCEDURE Get (           tbl : Default;
>                READONLY   k   : Key.T;
>                VAR(*OUT*) v   : Value.T): BOOLEAN =
>   VAR
>     x   : Node := tbl.h.hi;
>     cmp : Cmp;
>   BEGIN
>     WHILE (x # NIL) DO
>       cmp := tbl.keyCompare (k, x.key);
>       IF cmp = 0 THEN  v := x.value;  RETURN TRUE; END;
>       IF (cmp < 0)
>         THEN x := x.lo; (* line 145 *)
>         ELSE x := x.hi;
>       END;
>     END;
>     RETURN FALSE;
>   END Get;
>
> where Node is defined as 
>
> TYPE
>   Node = REF RECORD
>     key     : Key.T;
>     value   : Value.T;
>     lo      : Node := NIL;
>     hi      : Node := NIL;
>     priority: INTEGER    (* random num; tree is a heap on these *)  
>   END;
>
> It seems odd to me that, under these circumstances, x := x.lo would
> cause any sort of checking activity...
>
> I'm using a CM3 that's about a month old, on FreeBSD4.
>
>      Mika
>
> P.S. Needless to say, the code in question runs about 10x faster under
> PM3 than with this relatively new CM3...  but my m3gdb is having trouble
> with PM3's LONGREALs for some reason.
>
>