How to use the crate?

[saona-raimundo]

Hi! Maybe I am doing something really wrong since I have never used ffi in Rust...

I wanted to run the README example in my computer and I have the following error when compiling.

   Compiling graphviz-ffi v0.1.2
error: failed to run custom build command for `graphviz-ffi v0.1.2`

Caused by:
  process didn't exit successfully: `C:\Users\rsaonaur\projects\knowledge\target\debug\build\graphviz-ffi-b606b415f266dceb\build-script-build` (exit code: 101)
  --- stdout
  cargo:rustc-link-lib=gvc
  cargo:rustc-link-lib=cgraph

  --- stderr
  thread 'main' panicked at 'Unable to find libclang: "couldn't find any valid shared libraries matching: ['clang.dll', 'libclang.dll'], set the `LIBCLANG_PATH` environment variable to a path where one of these files can be found (invalid: [])"', C:\Users\rsaonaur\.cargo\registry\src\github.com-1ecc6299db9ec823\bindgen-0.59.1\src/lib.rs:2117:31
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I am not sure what it means :/
Do I have to install libclang before using this crate?
Maybe I have to obtain gvc and cgraph from graphviz to make the link?

Again, sorry if this is a very basic question.

[pgimalac]

So you need to link with graphviz (gvc and cgraph) to be able to use this crate, and I guess from your error message that these libraries need clang to run (or that Rust need clang to run ?).

Try to install clang (and graphviz if it's not already done).

Fyi I tried on my computer and it worked well, I guess I have everything needed already installed.
I looked at the list of libraries used and there wasn't libclang, but I guess that's system dependent... (there was libgcc though)

[saona-raimundo]

Hi, thank you for helping me! and sorry for bothering

I installed clang (through chocolatey llvm), and of course I had installed graphviz. Now the error message for me is the following.

   Compiling graphviz-ffi v0.1.2
error: failed to run custom build command for `graphviz-ffi v0.1.2`

Caused by:
  process didn't exit successfully: `C:\Users\rsaonaur\projects\knowledge\target\debug\build\graphviz-ffi-b606b415f266dceb\build-script-build` (exit code: 101)
  --- stdout
  cargo:rustc-link-lib=gvc
  cargo:rustc-link-lib=cgraph

  --- stderr
  wrapper.h:1:10: fatal error: 'graphviz/gvc.h' file not found
  wrapper.h:1:10: fatal error: 'graphviz/gvc.h' file not found, err: true
  thread 'main' panicked at 'Unable to generate bindings: ()', C:\Users\rsaonaur\.cargo\registry\src\github.com-1ecc6299db9ec823\graphviz-ffi-0.1.2\build.rs:46:10

I tried to put the files graphviz/gvc.h and graphviz/cgraph.h in the crate root folder (taken from the gitlab repository of graphviz), but it seems it is not that easy.

Could it be that I have to install the development version of graphviz? I remember something about this on the official website. I just installed graphviz through chocolatey.

[pgimalac]

I never developed anything on Windows so I don't exactly know how it works, but I guess there are folders somewhere which contain library header files. For it to work, you should have in one such directory a "graphviz" directory with the two wanted header files.

Indeed, I think you need the development version which should contain the headers.

[saona-raimundo]

I did not need the development version!

Here is an answer about where to put .h files in windows so they can be found and called like #include <graphviz/gvc.h> (used by wrapper.h). https://superuser.com/questions/297872/where-to-put-libraries-and-headers-on-windows-coming-from-unix
In short, "Install to its own location under Program Files or Program Files\Common Files."

I copied the files that come with graphviz installation, in my case under C:\Program Files\Graphviz 2.44.1\include.

Sorry to bother you again, but now it should be about the crate itself and not Windows installation.
It seems that stdin and stdout used in the README example are not in the root. I get this error.

error[E0432]: unresolved imports `graphviz_ffi::stdin`, `graphviz_ffi::stdout`
 --> src\main.rs:2:89
  |
2 |     agclose, agread, fopen, gvContext, gvFreeContext, gvFreeLayout, gvLayout, gvRender, stdin,
  |                                                                                         ^^^^^ no `stdin` in the root
3 |     stdout,
  |     ^^^^^^ no `stdout` in the root

I tried to replace them following this question without luck.

[pgimalac]

It seems like stdin and stdout aren't exported in the windows version, which is weird...

I looked for stdin and stdout in the libc crate, without success, but I found STDIN_FILENO and STDOUT_FILENO, so using the C function fdopen you can replace stdin with fdopen(libc::STDIN_FILENO, to_c_string!("r")) and stdout with fdopen(libc::STDOUT_FILENO, to_c_string!("w")).

If you don't want to use libc, STDIN_FILENO should be the integer 0 and STDOUT_FILENO the integer 1.

I looked at your link after writing this, what did you try specifically ? Using fdopen like above didsn't work for you ?

[saona-raimundo]

Thank you!

Changing stdin and stdout

Changing stdin for fdopen(0, to_c_string!("r")) and stdout for fdopen(1, to_c_string!("w")), where fdopen is imported from graphviz_ffi makes the program compile :D

Now when I run it, it shows a link problem with 'gvc.lib'... and I know this is very caotic with link problems, so I will just give up for now.

I looked at your link after writing this, what did you try specifically ?

I tried to change stdout as an import from graphviz_ffi to this:

extern {
    static stdout: *mut libc::FILE;
}

but the types are different, so there was a compile error.

On link problem

Just in case you have something in mind, I tried to link the headers directly to my graphviz installation, by changing wrapper.h by

#include "Direct path to graphviz/gvc.h"
#include "Direct path to graphviz/cgraph.h"

but this did not solve the linking problem.

Workaorund

This is totally unsafe and so on... but works for me.

My workaround to use graphviz from rust is using the command line app dot like so:

Command::new("dot")
      .args(["-Tsvg", "my.dot", "-o", "my.svg"])
      .spawn()?
      .wait()?;

where my.dot is written somehow from Rust and then I can read the output from the output file of dot, in this case my.svg.

[pgimalac]

Now when I run it, it shows a link problem with 'gvc.lib'... and I know this is very caotic with link problems, so I will just give up for now.

Could you show the error message please ?

I tried to replace the path to the header files like you did and it built correctly, what error message did you have ?

The workaround is better than nothing ! If the only thing you need is to call dot, it's better than nothing ; the issue would be if you need something more specific only available using the C library directly...

[saona-raimundo]

Surely, this is the error I get.

   Compiling hello_graphviz v0.1.0 (C:\Users\rsaonaur\projects\hello_graphviz)
error: linking with `link.exe` failed: exit code: 1181
  |
  = note: "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\VC\\Tools\\MSVC\\14.29.30133\\bin\\HostX64\\x64\\link.exe" "/NOLOGO" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.100sk3mkpxtbqh8w.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.12o4ajvr1xupn8qi.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.1jcirr2d6e2pmvcb.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.1l34so64ccg6v7l.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.1pcshjjwdbszlyia.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.213jp44txkbo56od.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.26k1auu6097vufyi.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.288lbr0oc11kdwyy.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.29psywq2rpd8hy8b.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.2bb3qwoil3v90so0.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.2e7n8srcl2h1qd0q.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.2kik98wxt5kdjsli.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.2tmxmujxz5xz79sg.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.2zhz4xw0ezv0palw.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.32gk0bn3d6tgt4lr.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.32s6hw1weyy87ack.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.37cdocsrj50444xz.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.387q5hm9odjbcdgy.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.38vfuyy09huu4wj6.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.3d8r2hxwubg3273j.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.3ea97bxg403n1pdd.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.3hdxnqo7w4ynbixd.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.3x5uvgp4zpu0lqkb.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4ciqidkrjowbwkof.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4dax5j63yyg1hnkg.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4ifrjysyv04jf3hw.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4q7yj65vcnuzpaen.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4vgldcwn8su8syij.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4y3tqwyg1gf4o18f.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.4zbe65sipt11nfmg.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.52n2gga9yheo97qu.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.52ox7v8znho0nbs7.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.54p53etnwhkzpoyy.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.58ojkvp5i6lh2n8y.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.ri8qjmd2526v7v.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.y7m10n0lvlwrflt.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.zu5ovl39vfn2i65.rcgu.o" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.18zi9i162aayc851.rcgu.o" "/LIBPATH:C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps" "/LIBPATH:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\libgraphviz_ffi-3064a0b1c2dfbf33.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libstd-3d786a338e3fbd3c.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libpanic_unwind-c7722f94ca812e0f.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libstd_detect-f6ac1aae8e3d5b95.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\librustc_demangle-8244d5c29082f380.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libhashbrown-c29ed8b388a545d6.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\librustc_std_workspace_alloc-daec0207219073db.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libunwind-e1164c8529217a2a.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libcfg_if-78991d36592dccee.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\liblibc-3e2bb97c5be118b7.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\liballoc-d5bd6400adb9fa95.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\librustc_std_workspace_core-07dcecfd1f459221.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libcore-f0c150dc0abba70a.rlib" "C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libcompiler_builtins-0f3806ca1d72c7be.rlib" "gvc.lib" "cgraph.lib" "kernel32.lib" "ws2_32.lib" "advapi32.lib" "userenv.lib" "kernel32.lib" "msvcrt.lib" "/NXCOMPAT" "/LIBPATH:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "/OUT:C:\\Users\\rsaonaur\\projects\\hello_graphviz\\target\\debug\\deps\\hello_graphviz.exe" "/OPT:REF,NOICF" "/DEBUG" "/NATVIS:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\intrinsic.natvis" "/NATVIS:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\liballoc.natvis" "/NATVIS:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\libcore.natvis" "/NATVIS:C:\\Users\\rsaonaur\\.rustup\\toolchains\\stable-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\libstd.natvis"
  = note: LINK : fatal error LNK1181: cannot open input file 'gvc.lib'

Let me know if you would like any other info, I am happy to tell you.