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From: Richard Koch <n1gp@hotmail.com>
To: <crossgcc@sourceware.org>
Subject: Compiler Memory Alignment Issue
Date: Thu, 02 Feb 2012 18:15:00 -0000
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Hello List,

I'm seeing an alignment issue when I'm incrementing a pointer.

Using the program below I found that the cross compiler I built from
crosstools-ng-1.13.3, interprets the "*(ptr + 1)" as adding 1 BYTE to ptr. =
It should
know that ptr is declared as a pointer to an integer and interpret "*(ptr +=
 1)"
as adding 4 BYTES to ptr.

An older cross compiler from Technologics, crosstool-linux-gnueabi-2005q3-2=
, doesn't
exhibit this problem and interprets the pointer addition correctly. So does=
 the
native gcc on the target. I would prefer to use crosstools-ng.

The target is a Technologics TS-7350 ARM920T (EP9302).

I'm wondering if there may be something I haven't set properly in the cross=
tool-ng's
configuration?

The configuration file I'm using can be seen here:

=A0=A0=A0 http://home.comcast.net/~n1gp/ct_config

PROGRAM:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

int main()
{
=A0=A0=A0=A0=A0=A0=A0 unsigned char buffer[8], i;
=A0=A0=A0=A0=A0=A0=A0 int *ptr =3D (int *) buffer;

=A0=A0=A0=A0=A0=A0=A0 printf("size of int is: %d\n", sizeof(int));
=A0=A0=A0=A0=A0=A0=A0 memset(buffer, 0xff, sizeof buffer);

=A0=A0=A0=A0=A0=A0=A0 *(ptr + 1) =3D 0x1234;

=A0=A0=A0=A0=A0=A0=A0 for (i=3D0; i<(sizeof(buffer) +1); i++)
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 printf("buffer[%d]=3D%x\n", i=
, buffer[i]);
}


RESULTS WITH crosstool-linux-gnueabi-2005q3-2:

size of int is: 4
buffer[0]=3Dff
buffer[1]=3Dff
buffer[2]=3Dff
buffer[3]=3Dff
buffer[4]=3D34
buffer[5]=3D12
buffer[6]=3D0
buffer[7]=3D0
buffer[8]=3D0

RESULTS WITH crosstools-ng:

size of int is: 4
buffer[0]=3Dff
buffer[1]=3D34
buffer[2]=3D12
buffer[3]=3D0
buffer[4]=3D0
buffer[5]=3Dff
buffer[6]=3Dff
buffer[7]=3Dff
buffer[8]=3D8

Thanks,

Rick


=20=09=09=20=09=20=20=20=09=09=20=20

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