Re: Interfacing with C - pointer problem

On Jan 30, 1:10 pm, tmo...@xxxxxxx wrote:
type LPSTR is access all String;

This does not work correct. What I found is, that data'Address is 32
bit and LPSTR is 64 bit.

Because LPSTR points to a dynamic size string and thus needs to
carry along bounds information. A C LPSTR does not point to a dynamic
string, but instead points to a single character - the first in the
string. So the match is
type LPSTR is access Interfaces.C.Char;
procedure C_Func (x : LPSTR); -- expects an address (C-pointer, 32-bit)
and then
data : Interfaces.C.char_array := Interfaces.C.To_C("ABC");
and
C_Func (data(data'first)'unchecked_access);

Or perhaps better:

procedure C_Func (x : Interfaces.C.Strings.chars_ptr);

data : aliased Interfaces.C.char_array := Interfaces.C.To_C
("ABC");

C_Func (Interfaces.C.Strings.To_Chars_Ptr (data'unchecked_access));

May as well use the stuff Ada provides for this exact purpose.

-- Adam

.

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