Malloc and assignment in h8300-elf

["D.Venkatasubramanian, Noida" <dvenkat at noida dot hcltech dot com>]

Hi,

I was compiling a small program with malloc and memcpy 
using h8300-elf-gcc -mh. 
(I am not using -mint32 flag.)

When I run this program in the simulator, the simulator hangs. 
Also, there is a compilation warning generated.

On looking at the disassembly, I found

        d = ((char *)malloc(6));
     1d8:       79 00 00 06     79 00 00 06       mov.w #0x6,r0
     1dc:       5e 00 03 8a     5e 00 03 8a       jsr   @0x38a:0
     1e0:       0d 02           0d 02             mov.w r0,r2
     1e2:       17 f2           17 f2             exts.l        er2
     1e4:       01 00 6f e2     01 00 6f e2 ff f8 mov.l er2,@(0xfff8:16,er6)
     1e8:       ff f8

Why is this instruction generated?

exts.l        er2

At this point r0 has some value 0000xxxx which is moved into r2, but as 
soon as this sign extension takes place, er2 becomes ffffxxxx. er2 is passed

into d.

The simulator seems to have a memory of 256 KB only, so won't ffffxxxx be 
beyond that?

The simulator goes into an infinite loop in byteloop in the h8300 specific 
memcpy.S

memcpy (d, s, 4);

00000d40 <byteloop>:
     d40:       1b 01           1b 01             subs  #0x1,er1
     d42:       68 1a           68 1a             mov.b @er1,r2l
     d44:       6c 8a           6c 8a             mov.b r2l,@-er0   <---
This instruction
     d46:       1f 83           1f 83             cmp.l er0,er3
     d48:       46 f6           46 f6             bne   .-10 (d40)

er3 has the beginning of dst and er0 has end of destination address 
at the start of this loop. er1 points to last byte of src.

At the instruction

mov.b r2l,@-er0

er0 had say ffff8273, then it becomes 007f8272, whereas it should have been
ffff8272.
er3 has ffff8271 (say). Naturally the comparison fails and this code gets
into an 
infinite loop.

I was trying to find, where the problem exists, in the d = malloc code or
here in 
byteloop?

Am I misinterpreting something? Please advice. The problem should be
reproducible from
the code given below.

Thanks and Regards,

Venky
________________________________________________

Program Listing


#include <fcntl.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

int main()
{
        char *s = "Help\n";
        char *d;

        d = ((char *)malloc(6));
        memcpy (d, s, 4);
        d[5] = '\0';
        printf ("String d = %s\n", d);
        return 0;
}