ARM compiler misbehaves ?

[Svein-Erik Skjelbred <ixdp425 at skjelbred dot com>]

Hello
We are encontering something that we think is a compiler bug. Running on 
a normal PC it works. We have taken everything out of normal code and 
made the following sample code.

typedef struct
{
	unsigned char test_char;
	unsigned short test_short;
}  __attribute__ ((__packed__)) test_struct;

int main(void)
{
	test_struct test_var = {0x12, 0x3456};
	unsigned short* test_pointer;
		
	printf("test_var.test_char %x\n", test_var.test_char);
	printf("test_var.test_short %x\n", test_var.test_short);
	
	test_pointer = &test_var.test_short;
	*test_pointer = 0x789A;

        printf("test_var.test_char %x\n", test_var.test_char);
        printf("test_var.test_short %x\n", test_var.test_short);

	return 0;
}


ON A LINUX PC
$ gcc --version
gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5)
Copyright (C) 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc test.c
$ ./a.out
test_var.test_char 12
test_var.test_short 3456
test_var.test_char 12
test_var.test_short 789a


$ armv5b-linux-gcc --version
armv5b-linux-gcc (GCC) 3.3.3
Copyright (C) 2003 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


$ armv5b-linux-gcc --static test.c
<Transfer to target>
# ./a.out
test_var.test_char 12
test_var.test_short 3456
test_var.test_char 78 -----------------> Short started 1 byte to early
test_var.test_short 9a56
#

We think that the compiler takes the odd address and maskes out the east
significant bit.

Svein-Erik Skjelbred



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