Fix determining the path to the binary.

If the binary name is resolve from the shell $PATH
environment variable, this previously failed and crashed
with an exception.

This change does some more effort to attempt trying to
find the correct path in that case.

This fixes prusa3d#5542

Signed-off-by: Henner Zeller <h.zeller@acm.org>

src/PrusaSlicer.cpp

@@ -585,6 +585,37 @@ int CLI::run(int argc, char **argv)
     return 0;
 }
 
+static boost::filesystem::path CanonicalPathToBinary(const char *prog) {
+    boost::filesystem::path result;
+    // If the executable is invoked with an absolute or relative path,
+    // we can extract it from there using system_complete().
+    //
+    // However this will fail if the binary is resolved by the shell
+    // from the PATH environment variable, then arv[0] will just be
+    // the "prusa-slicer" name to which system_complete will just prepend
+    // with $PWD and get a nonsense path (Bug #5542).
+    //
+    // On Linux, we use some operating system trick to find the true
+    // path of the binary: there the current running binary is symbolically
+    // linked from /proc/self/exe which we can resolve.
+    // It won't resolve anything on other platforms, but doesnt harm either.
+    //
+    // TODO: there might be other tricks needed on other operating systems.
+    for (const char *testpath : { prog, "/proc/self/exe" }) {
+        try {
+            result = boost::filesystem::system_complete(testpath);
+            result = boost::filesystem::canonical(result);
+            if (result.is_absolute())
+                return result;
+        }
+        catch (const boost::filesystem::filesystem_error& e) {
+            // Couldn't resolve. Let's continue our quest.
+        }
+    }
+    // Give up, fall back to simple system_complete.
+    return boost::filesystem::system_complete(prog);
+}
+
 bool CLI::setup(int argc, char **argv)
 {
     {
@@ -598,13 +629,13 @@ bool CLI::setup(int argc, char **argv)
         }
     }
 
-    boost::filesystem::path path_to_binary = boost::filesystem::system_complete(argv[0]);
+    const boost::filesystem::path path_to_binary = CanonicalPathToBinary(argv[0]);
 
     // Path from the Slic3r binary to its resources.
 #ifdef __APPLE__
     // The application is packed in the .dmg archive as 'Slic3r.app/Contents/MacOS/Slic3r'
     // The resources are packed to 'Slic3r.app/Contents/Resources'
-    boost::filesystem::path path_resources = boost::filesystem::canonical(path_to_binary).parent_path() / "../Resources";
+    boost::filesystem::path path_resources = path_to_binary.parent_path() / "../Resources";
 #elif defined _WIN32
     // The application is packed in the .zip archive in the root,
     // The resources are packed to 'resources'
@@ -618,7 +649,7 @@ bool CLI::setup(int argc, char **argv)
     // The application is packed in the .tar.bz archive (or in AppImage) as 'bin/slic3r',
     // The resources are packed to 'resources'
     // Path from Slic3r binary to resources:
-    boost::filesystem::path path_resources = boost::filesystem::canonical(path_to_binary).parent_path() / "../resources";
+    boost::filesystem::path path_resources = path_to_binary.parent_path() / "../resources";
 #endif
 
     set_resources_dir(path_resources.string());