igjoshua / coffi Goto Github PK

I'm trying to use libclang to auto-generate struct layouts for use with coffi. As a sanity check, I wanted to make sure that the size of a struct reported by clang matched mem/size-of. It generally does, but I noticed there's a size difference when a struct includes pointers.

For example:

#include <stdio.h>

typedef struct S1 {
    char c;
    void* p;
} S1;

int main(int n, char** args){
    printf("size: %lu\n", sizeof(S1));
}

The above gives a size of 16, but the same struct definition in coffi gives 9:

(defalias ::S1
  (layout/with-c-layout
   [::mem/struct
    [[:c ::mem/char]
     [:p ::mem/pointer]]]))

(mem/size-of ::S1) ;; 9

It doesn't seem like there's anything wrong with the implementation. The byteAlignment of ValueLayout/ADDRESS is 1. I'm not really sure whether I'm using clang wrong or if there's something else going on. Either way, I thought I'd report it in case there is some improvement to be made.

This library looks for useful! Unfortunately, my first tests hit a wall right away. If I start the JVM with the --add-modules=jdk.incubator.foreign flag set, I get:

java.lang.module.FindException: Module jdk.incubator.foreign not found

... and if I remove that flag, I get an error telling me that it can't find the jdk.incubator.foreign.Addressable class.

This is on an aarch64 Mac/MacOS 12.6.1. My JDK info:

java -version
openjdk version "19.0.1" 2022-10-18
OpenJDK Runtime Environment Homebrew (build 19.0.1)
OpenJDK 64-Bit Server VM Homebrew (build 19.0.1, mixed mode, sharing)

Anything I should try? Thanks in advance.

defvar calls ensure-symbol which is private (in develop branch)

typedef struct S1 {
    char c;
    void* p;
} S1;

extern void f1(S1* s){
    
}

(defalias ::S1
  (layout/with-c-layout
   [::mem/struct
    [[:c ::mem/char]
     [:p ::mem/pointer]]]))

(defcfn
 f1
 ""
 "f1"
  [[:coffi.mem/pointer ::S1]]
 :coffi.mem/void)
;; Syntax error compiling at (*cider-repl workspace/clong:localhost:58963(clj)*:40:33).
Unable to resolve symbol: scope12651 in this context

It's likely that I'm doing something dumb here, but I thought I'd file an issue just in case.

Also, I saw the following notes in the readme:

In cases where a pointer to some data is required to pass as an argument to a native function, but doesn't need to be read back in, the pointer primitive type can take a type argument.

I'm not actually sure what you mean by "doesn't need to be read back in".

This interface was removed going from JDK 19 to JDK 20:

https://bugs.openjdk.org/browse/JDK-8295045