mxcl•2y ago

getting errno with ffi

I am using ffi to call execv and need to get the value of errno for failures, but can’t see how I can do that.

10 Replies

ioB•2y ago

@aapoalas, as the local ffi wizard, do you have any input here?

Seems like errno is defined by a macro so I'm not sure it's exactly readable directly with Deno FFI but if it is then it's something like this:

Deno.dlopen("",
  {
    errno: {
      type: "int32"
    }
  });

Deno.dlopen("",
  {
    errno: {
      type: "int32"
    }
  });

Hm yeah, seems to be somewhat platform specific. Here's how it'd work for Android:

const lib = Deno.dlopen("",
{
  __geterrno: {
    parameters: [],
    result: "pointer",
  },
});

const errnoPointer = lib.symbols.__geterrno();
const errno = new Deno.UnsafePointerView(errnoPointer).getInt32();

const lib = Deno.dlopen("",
{
  __geterrno: {
    parameters: [],
    result: "pointer",
  },
});

const errnoPointer = lib.symbols.__geterrno();
const errno = new Deno.UnsafePointerView(errnoPointer).getInt32();

mxclOP•2y ago

thanks both!

Deno.dlopen("",
  {
    errno: {
      type: "int32"
    }
  });

Deno.dlopen("",
  {
    errno: {
      type: "int32"
    }
  });

works (darwin/vanilla linux)

AapoAlas•2y ago

Happy to help! If you have your code up somewhere or put it up later, let me know, I'm interested in seeing all the wonderful and wacky things people come up with using FFI 🙂

ioB•2y ago

Pretty sure this is for tea curious what this is for specifically though

AapoAlas•2y ago

Like brewing?

ioB•2y ago

https://github.com/teaxyz/cli

GitHub

GitHub - teaxyz/cli: the next-generation, cross‐platform package ma...

the next-generation, cross‐platform package manager - GitHub - teaxyz/cli: the next-generation, cross‐platform package manager

ioB•2y ago

TLDR; package manager written in Deno https://github.com/teaxyz/cli/pull/621/files oh wow this is a cursed PR

mxclOP•2y ago

thanks for the help here both. This use of ffi is now live!

ioB•2y ago

Happy to help as always Max