I have a data-conversion function in our ARM9 code which uses varargs.
I've been using an arm-elf yagarto distribution from a couple of years
ago, with no problems.  Recently, we upgraded to the arm-eabi-none
yagarto package from the yagarto site, and I'm finding that we now have
problems with floating point values.  What I eventually discovered is
that doubles are being forced to 8-byte boundaries, and the existing
varargs floating-point handler didn't expect to find gaps in the args.

I can manually check the pointer and force it up to an eight-byte
boundary (in fact, I did that, and that fixed the issue entirely), but
I'd like to know why this has suddenly started happening.

Is there a compiler switch that specifies data alignment on the stack,
or in function calls, or something like that??  And why would it be
defaulting to 8-byte boundaries on a 32-bit (4-byte) architecture??

I would appreciate any advice or insights that anyone could provide on
these issues.