On 12/15/2014 12:39 PM, Richard Earnshaw wrote:
On 12/12/14 23:50, Florian Weimer wrote:
On 12/12/2014 08:02 PM, Jeff Law wrote:
It'd probably work for the specific cases Florian wants to tackle, but
I'd consider it highly non-portable.
I agree, that's why I asked for something “GCC-portable”.
Don't go this way. Seriously, you can't assume that a future platform
ABI won't break if you do. ABI's at this level really aren't controlled
by GCC, which just has to conform to whatever the platform ABI requires.
We were very close in AArch64 to defining the ABI for variadics to push
all variadic (from the ... onwards) arguments onto the stack - it leads
to a very simple ABI from an implementation viewpoint and eliminates
much of the grotty code around reconstructing the parameter list.
This would still work except in a very pathological corner case which
cannot happen with glibc (the stack cannot be empty when the open
function is called because all user code runs with a non-empty stack).
Did you shy away from the simple implementation because of too many
interop failures?
--
Florian Weimer / Red Hat Product Security
