I haven't called a custom DLL in some time now; since I have more spare time, I was noodling around with old code.
Took me a while to notice what was going on; "pass by reference" where you send a J array to a DLL to be written to wasn't working the way it had in the past. It actually is documented, but I had to read about it in the forum (this was <http://jsoftware.2058.n7.nabble.com/j807-cd-pass-array-arguments-td80898.html#a80909> helpful) to understand what it meant. I propose that memu be documented here as well as on the "calling DLLs" page https://code.jsoftware.com/wiki/Guides/DLLs/Memory_Management Also the use of & vs * in the signature is far from clear to me in the calling DLL <https://code.jsoftware.com/wiki/Guides/DLLs/Calling_DLLs>s page. In the past, if I had a function signature like this, and want variable XX to be populated in the dll (and returned to J), everything would be fine: (for a C function int MyIntMod (int len, int vec[]) which modifies the vector of length len ) cmd=. LIBNAME,' MyIntMod i i *i' XX =. nr $ 1-1 cd cmd;nr;XX (etc etc) Now, it only works if I do the following cmd=. LIBNAME,' MyIntMod i i &i' XX =. memu nr $ 1-1 cd cmd;nr;XX Is this the correct way for modify a vector passed by reference in a DLL? If so, when I read the documentation, it looks like it should work with *i as well. "The * type is a pointer to values. A * can be followed by c w u s i l x f d or j to indicate the type of values. The DLL can read or write this memory. The memory is unaliased. The & type is same as * except the memory is not unaliased as it is assumed to be constant." Can someone add a sentence for my (presumably common) dll use case? I was able to figure it out, but it took me a bit. -SL ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
