On 12/24/2012 07:53 PM, Roger Cruz wrote:
>
>
> I am compiling this piece of code from an open source project that I
> wish not to have to change. The problem is that when compiled for
> ARM, it generates an LDRD instruction, which when executed, causes a
> bus error since the address in ptr is not doubleword aligned.
Well, that's going to be tough. Your code isn't legal C, and a
compiler is not obligated to generate anything sensible for it. You
can't just convert an arbitrary byte pointer to a UINT64* and expect
working code. If you lie to the compiler it will bite you.
> I know I can change the code but I prefer to leave it intact as
> there may be many more instances of this and I don't wish to
> maintain the code.
There's no point talking about "maintenance" because the code is
already broken.
> 248 static DWORD64 dwarf2_get_u8(const unsigned char* ptr)
> 249 {
> 250 return *(const UINT64*)ptr;
> 251 }
This is the right way to do it:
static DWORD64 dwarf2_get_u8(const unsigned char* ptr)
{
UINT64 poo;
memcpy(&poo, ptr, sizeof poo);
return poo;
}
If GCC can detect that ptr is correctly aligned, it will generate an
LDRD or LDM instruction, as appropriate.
> Happy Holidays,
You too! :-)
Andrew.
