Re: Compiler Memory Alignment Issue

["Yann E. MORIN" <yann dot morin dot 1998 at free dot fr>]

Richard, Bob, All,

On Friday 03 February 2012 11:16:27 Bob Dunlop wrote:
> On Thu, Feb 02 at 01:15, Richard Koch wrote:
> > I'm seeing an alignment issue when I'm incrementing a pointer.

I Just tried your .config and your sample C code, and it seems to work here
(with the buffer overflow fixed):

$ arm-none-linux-gnueabi-gcc -o ess ess.c
$ qemu-arm -L ..../arm-none-linux-gnueabi/sysroot ./ess
size of int is: 4
buffer[0]=ff
buffer[1]=ff
buffer[2]=ff
buffer[3]=ff
buffer[4]=34
buffer[5]=12
buffer[6]=0
buffer[7]=0

The assembly code corresponding to the assignment is (from gdb's disas /m):
14          *(ptr + 1) = 0x1234;
   0x00008400 <+56>:    ldr     r3, [r11, #-16]
   0x00008404 <+60>:    add     r2, r3, #4
   0x00008408 <+64>:    mov     r3, #4608       ; 0x1200
   0x0000840c <+68>:    add     r3, r3, #52     ; 0x34
   0x00008410 <+72>:    str     r3, [r2]

As you can see for @0x8404, an offset of #4 is added to the address of the
array.

Regards,
Yann E. MORIN.

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