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Different architectures use different types for va_list:
x86_64 uses an 1-length array of struct type[0]:
typedef struct {
unsigned int gp_offset;
unsigned int fp_offset;
void *overflow_arg_area;
void *reg_save_area;
} va_list[1];
aarch64 uses a struct type[1]
typedef struct {
void *__stack;
void *__gr_top;
void *__vr_top;
int __gr_offs;
int __vr_offs;
} va_list;
Consequently, C functions which takes a va_list as an argument,
such as vprintf, may pass va_list in different ways depending on
the architecture.
On x86_64, va_list is an array type, so parameter decays to a pointer
and passing the address of the va_list is correct.
On aarch64, the va_list struct is passed by value, but since it is
larger than 16 bytes, the parameter is replaced with a pointer to
caller-allocated memory. Thus, passing the address as an l argument
happens to work.
However, this pattern of passing the address of the va_list to
vprintf doesn't extend to other architectures. On riscv64, va_list
is defined as
typedef void *va_list;
which is *not* passed by reference. This means that tests that call
vprintf using the address of a va_list (vararg1 and vararg2) will
not work on riscv.
To fix this while keeping the tests architecture-neutral, add a
small wrapper function to the driver which takes a va_list *, and
let the C compiler deal with the details of passing va_list by
value.
[0] https://c9x.me/compile/bib/abi-x64.pdf#figure.3.34
[1] https://c9x.me/compile/bib/abi-arm64.pdf#%5B%7B%22num%22%3A63%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C52%2C757%2C0%5D
[2] https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#va_list-va_start-and-va_arg$
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