DllCall which returns a STRUCT

[paultibb]

Hi, All. I've been struggling with this one for a bit now and after quite a bit of searching, I have still not found an answer.

I have the following C function definition which takes two pointers as inputs and returns a structure.

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typedef struct match_result
{
	int success;
	int should_update;
	int score;
} match_result;

match_result match(void* authenticator, void* args);

How do I form the DllCall function to get the result from the returned structure?

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retval := DllCall( "match.dll\match", "Ptr", authenticator, "Ptr", args, "Cdecl ??????")

Thoughts?

Thanks!

[iseahound]

No one seems to be answering your question

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retval := DllCall( "match.dll\match", "Ptr", authenticator, "Ptr", args, "ptr") ; try "cdecl ptr" if this doesn't work.

Then to retrieve your values,

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struct1 := NumGet(retval+0, 0, "int) ; Note the +0 this is AutoHotkey v1 being really dumb.

[Descolada]

Try

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match_result := DllCall( "match.dll\match", "Ptr", authenticator, "Ptr", args, "Ptr")
success := NumGet(match_result+0, 0, "Int")
should_update := NumGet(match_result+0, 4, "Int")
score := NumGet(match_result+0, 8, "Int")

And be sure to check out jeeswg's awesome DllCall tutorial

[swagfag]

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VarSetCapacity(match_result, 12)
pmatch_result := DllCall( "match.dll\match", "Ptr", &match_result, "Ptr", authenticator, "Ptr", args, "CDecl Ptr")
success := NumGet(match_result, 0, "Int")
should_update := NumGet(match_result, 4, "Int")
score := NumGet(match_result, 8, "Int")

[paultibb]

Thank you all for the thoughtful responses.

You win, @swagfag. Is this documented anywhere?

[swagfag]

probably, on some page somewhere in the C ANSI standard

[lexikos]

It's a detail of the x86/64 calling convention, not the C standard. I think I've posted about it before, in more detail.

[Helgef]

There was a related discussion, with links, which might be interesting for reference. See Passing structure to function.

Cheers.