From 3eaf8675650e79c61dcbe442b7c9df83a9ec5d28 Mon Sep 17 00:00:00 2001
From: Guillaume Bouchard <guillaum.bouchard@gmail.com>
Date: Sat, 16 Sep 2017 14:28:57 +0200
Subject: [PATCH] More robust dependency lookup

---
 README.md   | 24 +++++++++++++++++++-----
 default.nix |  2 +-
 nixGL       | 28 +++++++++++++++-------------
 3 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/README.md b/README.md
index 2ebebe0..9e4d376 100644
--- a/README.md
+++ b/README.md
@@ -46,13 +46,27 @@ nixGL program args
 
 # Limitations
 
-The idea is really simple and should work reliably. However there is still two configurations variables hardcoded in the wrapper. Open a bug / pull request if this does not work on your distribution / driver.
+The idea is really simple and should work reliably in most cases.
 
-## Library paths
+However there is still two configurations variables hardcoded in the wrapper.
 
-The path of where the `libGL.so` library can be found on your system, usually `/usr/lib`.
+- `ignored`: the list of all nix packages which may contain a wrong `libGL.so`.
+- `systemLibs`: the list of where on the host system the `libGL.so` can be found.
 
-## Name of the Nix package which contains `libGL.so`
+Open a bug / pull request if this does not work on your distribution / driver.
 
-This package will be ignored by the wrapper. It is currently hardcoded as `mesa-noglu` but this can be fixed.
+It works with `primus`, but there is some artifacts.
 
+## Fundamental issue
+
+If your program libraries depends on different version of the same library, for example, this dependency tree:
+
+```
+program
+   libFoo-1.2
+      libBar-1.4
+   libTurtle-1.6
+      libBar-1.2
+```
+
+One version or the other of `libBar` may be used. In practice this does not happen a lot.
\ No newline at end of file
diff --git a/default.nix b/default.nix
index b570c0d..9f1e8b7 100644
--- a/default.nix
+++ b/default.nix
@@ -8,7 +8,7 @@ rec {
      name = "nixGL-${version}";
      version = "1.0.0";
 
-     buildInputs = [ pkgs.python3 pkgs.which pkgs.patchelf ];
+     buildInputs = [ pkgs.python3 pkgs.which pkgs.binutils ];
      outputs = [ "out" ];
 
      src = ./.;
diff --git a/nixGL b/nixGL
index 481dfda..6326959 100755
--- a/nixGL
+++ b/nixGL
@@ -16,18 +16,19 @@ systemLibs = [b"/usr/lib", b"/lib"]
 cmd = (prog, *args) = sys.argv[1:]
 realProg = subprocess.check_output(["which", prog]).strip()
 
-# extract rpath of the program
-rpaths = map(bytes.strip, subprocess.check_output(
-    ['patchelf', '--print-rpath', realProg]).split(b':'))
+# extract libs deps of the program
+paths = []
+for line in subprocess.check_output(['ldd', realProg]).split(b'\n'):
+    line = line.split()
+    if len(line) == 4:
+        lib = line[2]
+        path = os.path.dirname(lib)
 
-# filter rpath, removing ignored and empty paths
-dir = []
-
-for i in rpaths:
-    for c in ignored:
-        if c not in i:
-            if i.strip():
-                dir.append(i.strip())
+        for c in ignored:
+            if c in path:
+                break
+        else:
+            paths.append(path)
 
 # build the new environment
 newenv = os.environb
@@ -42,7 +43,8 @@ oldLdLibraryPath = newenv.get(b'LD_LIBRARY_PATH', b'').split()
 # This ensure three properties:
 # a) system library (and libOpenGL.so) are used AFTER the one of nix
 # b) the executible respect the LD_LIBRARY_PATH for an user viewpoint
-newLibraryPath = oldLdLibraryPath + dir + systemLibs
+newLibraryPath = b':'.join(oldLdLibraryPath + paths + systemLibs)
+
+newenv.update({b'LD_LIBRARY_PATH': newLibraryPath})
 
-newenv.update({b'LD_LIBRARY_PATH': b':'.join(newLibraryPath)})
 os.execvpe(prog, cmd, newenv)