Pointer difference

["Marc Nieper-Wißkirchen" <marc.nieper+gnu@gmail.com>]

Using gcc_jit_context_new_binary_op together with
GCC_JIT_BINARY_OP_MINUS, one can generate code to calculate the
difference of two pointer rvalues P and Q.

According to my experiments, however, the difference is not taken in
the C sense where the difference is the number of units between the
two pointers, which depends on the types of P and Q. Instead,
libgccjit seems to calculate the equivalent of GCC's (void *) P -
(void *) Q.

It's probably worth noting this in the documentation.

Thanks,

Marc

PS Coincidentally, libgccjit doesn't support the addition of an
integral type to a pointer type using GCC_JIT_BINARY_OP_PLUS; for that
one has to go through gcc_jit_context_new_array_access and then
gcc_jit_lvalue_get_address.