Hello,

I am trying to use libffi to call various functions, and my first try
was with printf(). As this is a variadic function, I used
ffi_prep_cif_var(). Everything seems to be working, except with floats,
which are not working, and are even generating wrong memory accesses
(detected by valgrind).

A similar function with ffi_prep_cif() and floats is working properly.

Could type promotion from float to double be the issue here ?
Does libffi handle type promotion in variadic calls or is it the
caller's job ?

I tested on a x86_64 computer both 64-bit and 32-bit versions (the
latter compiled with -m32) as well as ARM under qemu.
In all those cases, I didn't get the proper result with floats while
doubles are ok, as well as chars.
I've attached a sample source file that reproduces the problem and here
is the output of one test run:

 $ gcc $(pkg-config --cflags --libs libffi) -std=c99 -pedantic -Wall -Wextra libffi_variadic_printf.c -o libffi_variadic_printf
 $ ./libffi_variadic_printf
Non-variadic call:
[1.100000,2.200000,3.300000,4.400000,5.500000,6.600000,7.700000,8.800000,9.900000]
result is 83
Variadic call:
[0.000000,0.000000,0.000000,0.000000,0.000000,91750.390826,0.000000,0.000000,0.000000]
result is 87

Thanks,