Re: Calling C function with static array includes length and pointer
mwarning wrote: > Anyway, the D spec says: > "Static arrays are value types, but as in C static arrays are passed to > functions by reference and cannot be returned from functions." > (http://www.digitalmars.com/d/1.0/arrays.html#static-arrays) I've been thinking D2. :) In D2, fixed-sized arrays are value types and copied to and from functions: import std.stdio; int[2] foo(int[2] array) { writeln("in foo : ", &(array[0])); return array; } void main() { int[2] array; writeln("in main 1: ", &(array[0])); int[2] result = foo(array); writeln("in main 2: ", &(result[0])); } All three addresses are separate in D2. Ali
Re: Calling C function with static array includes length and pointer
On Tue, 22 Jun 2010 00:00:27 +0200, torhu wrote: > On 21.06.2010 23:30, mwarning wrote: >> Hi, >> >> I try to pass a static array to a variadic C function. Looks like the >> array is passed by values as expected, but the length and pointer are >> prepended, too. Is this intentional or a bug? >> >> http://pastebin.com/6ejFF37j > > I believe this works as intended. And arrays in D 1 are *not* passed by > value, ie. the data is not copied. > > From www.digitalmars.com/d/1.0/arrays.html: > > "a string literal is passed as a (length,pointer) combination to > variadic parameters" Thanks, I missed that section! > In other words, use stack.ptr if you want just the pointer. I wrap it into a struct, that will do it.
Re: Calling C function with static array includes length and pointer
On 21.06.2010 23:30, mwarning wrote: Hi, I try to pass a static array to a variadic C function. Looks like the array is passed by values as expected, but the length and pointer are prepended, too. Is this intentional or a bug? http://pastebin.com/6ejFF37j I believe this works as intended. And arrays in D 1 are *not* passed by value, ie. the data is not copied. From www.digitalmars.com/d/1.0/arrays.html: "a string literal is passed as a (length,pointer) combination to variadic parameters" In other words, use stack.ptr if you want just the pointer.
Re: Calling C function with static array includes length and pointer
On Mon, 21 Jun 2010 14:38:50 -0700, Ali Çehreli wrote: > mwarning wrote: >> Hi, >> >> I try to pass a static array to a variadic C function. Looks like the >> array is passed by values as expected, but the length and pointer are >> prepended, too. Is this intentional or a bug? >> >> http://pastebin.com/6ejFF37j > > Fixed sized arrays don't have ptr and length members: > > import std.stdio; > > void main() > { > int[5] array; > writeln(array.sizeof); // prints 20 writeln(array.ptr, ' > ', &array); // prints the save value > } Hm? You just have proved that they have. :> But those are not members of a struct/pair instance (as for dynamic arrays). They are compile time values. Whatever, it's me nitpicking. :) > The code you've pasted has this: > > extern(C) void* foo(uint x, ...) > { > Stdout("x: ")(x).nl; > Stdout("y: ")(*(&x + 1)).nl; //outputs 64! return null; > } > > The expression *(&x + 1) is undefined behavior, because (&x + 1) is not > valid, i.e. not specified to be accessible by the language. > > Ali True, the D spec doesn't specify the memory layout. But the C calling convention does (depending on the platform). Anyway, the D spec says: "Static arrays are value types, but as in C static arrays are passed to functions by reference and cannot be returned from functions." (http://www.digitalmars.com/d/1.0/arrays.html#static-arrays) It seems that D does a little more then just pass by value. It includes the pointer and length value as well. Btw.: smth. told me workaround/solution: wrap the static array in a struct.
Re: Calling C function with static array includes length and pointer
mwarning wrote: Hi, I try to pass a static array to a variadic C function. Looks like the array is passed by values as expected, but the length and pointer are prepended, too. Is this intentional or a bug? http://pastebin.com/6ejFF37j Fixed sized arrays don't have ptr and length members: import std.stdio; void main() { int[5] array; writeln(array.sizeof); // prints 20 writeln(array.ptr, ' ', &array); // prints the save value } The code you've pasted has this: extern(C) void* foo(uint x, ...) { Stdout("x: ")(x).nl; Stdout("y: ")(*(&x + 1)).nl; //outputs 64! return null; } The expression *(&x + 1) is undefined behavior, because (&x + 1) is not valid, i.e. not specified to be accessible by the language. Ali