Canonicalize the path returned by current_binary_dir()

mlx/backend/common/utils.cpp

@@ -12,7 +12,19 @@ std::filesystem::path current_binary_dir() {
     if (!dladdr(reinterpret_cast<void*>(&current_binary_dir), &info)) {
       throw std::runtime_error("Unable to get current binary dir.");
     }
-    return std::filesystem::path(info.dli_fname).parent_path();
+    // glibc reports dli_fname for a main executable as argv[0] verbatim, so it
+    // may be relative or contain "."; resolve it so that parent_path() of the
+    // result names the real parent directory.
+    std::filesystem::path path(info.dli_fname);
+    if (!path.has_parent_path()) {
+      // A bare argv[0] carries no location, and the two standard libraries
+      // disagree about it: libc++ would resolve it against the current working
+      // directory, inventing an unrelated answer.
+      return path.parent_path();
+    }
+    std::error_code ec;
+    auto resolved = std::filesystem::weakly_canonical(path, ec);
+    return ec ? path.parent_path() : resolved.parent_path();
   }();
   return binary_dir;
 }

mlx/backend/common/utils.h

@@ -6,12 +6,15 @@
 #include <tuple>
 #include <vector>
 
+#include "mlx/api.h"
 #include "mlx/array.h"
 
 namespace mlx::core {
 
-// Return the directory that contains current shared library.
-std::filesystem::path current_binary_dir();
+// Return the resolved directory that contains the current binary, with ".",
+// ".." and symlinks removed. Empty when the loader reports no location for
+// it, which glibc does for a PATH-launched executable.
+MLX_API std::filesystem::path current_binary_dir();
 
 inline int64_t
 elem_to_loc(int elem, const Shape& shape, const Strides& strides) {

tests/utils_tests.cpp

@@ -2,10 +2,22 @@
 
 #include "doctest/doctest.h"
 
+#include "mlx/backend/common/utils.h"
 #include "mlx/mlx.h"
 
 using namespace mlx::core;
 
+TEST_CASE("test current binary dir is resolved") {
+  auto dir = current_binary_dir();
+  // Empty is a legal result: a PATH-launched executable gets a bare argv[0],
+  // which carries no location to resolve.
+  if (dir.empty()) {
+    return;
+  }
+  CHECK(dir.is_absolute());
+  CHECK_EQ(dir, dir.lexically_normal());
+}
+
 TEST_CASE("test type promotion") {
   for (auto t : {bool_, uint32, int32, int64, float32}) {
     auto a = array(0, t);