On Thursday, 15 November 2018 at 21:12:39 UTC, Adam D. Ruppe
wrote:
On Thursday, 15 November 2018 at 21:07:51 UTC, pineapple wrote:
Is there a way to access this pointer?
It is passed as.. I think the final argument to the function.
(unless it is the first, do a quick test to find out).
Also, the calling convention documentation there doesn't
mention anything about 64-bit targets, are 64-bit registers
just not used?
It uses the C rules there, so look up the 64 bit C abi. I think
this is accurate
https://msdn.microsoft.com/en-us/library/ms235286.aspx
On the positive side: I see now how to return a 64-bit value from
a function in Windows x64! And I understand how the arguments are
coming in. This is very helpful.
On the less positive side: I still have no clue how to return my
16-byte struct. The Microsoft x64 ABI documentation I've seen so
far explains how return values of 8 bytes and fewer work, but
haven't explained how larger return values work. The obvious
answer of "RAX or EAX contains a pointer" is either not working
or my asm is wrong. (The latter is certainly a possibility.)
// Returns 128 (0x80)
ulong retTest() {
version(D_InlineAsm_X86_64) asm {
naked;
mov RAX, 0x80;
ret;
}
}
// Crashes
struct Result {
ulong low;
ulong high;
}
Result retTest() {
version(D_InlineAsm_X86_64) asm {
naked;
mov [RAX + 0], 0x80;
mov [RAX + 8], 0x80;
ret;
}
}
// Also crashes
struct Result {
ulong low;
ulong high;
}
Result retTest() {
version(D_InlineAsm_X86_64) asm {
naked;
mov [R9 + 0], 0x80;
mov [R9 + 8], 0x80;
ret;
}
}
