Fix configure.py issue with --clang_path.

If --clang_path is passed a symlink, an error would occur when building C++ files that had includes from the standard library. E.g., a possible error was:

ERROR: /root/.cache/bazel/_bazel_root/e4ab50d61a21943a819d1e092972a817/external/zlib/BUILD.bazel:5:11: Compiling zutil.c [for tool] failed: undeclared inclusion(s) in rule '@zlib//:zlib':
this rule is missing dependency declarations for the following files included by 'zutil.c':
  '/usr/lib/clang/17/include/stddef.h'
  '/usr/lib/clang/17/include/__stddef_max_align_t.h'
  '/usr/lib/clang/17/include/limits.h'
  '/usr/lib/clang/17/include/stdarg.h'

The clang on the PATH, such as /usr/bin/clang-17, is usually symlinked to a file such as /usr/lib/llvm-17/bin/clang, so this would typically cause issues when building with --clang_path.

The issue is that bazel gives such errors when compiled with a symlinked clang. Without --clang_path, we resolved symlinks, but not with --clang_path. This change also resolves symlinks with --clang_path.

PiperOrigin-RevId: 636004628

build_tools/configure/configure.py

@@ -69,27 +69,32 @@ def _find_executable(executable: str) -> Optional[str]:
   return None
 
 
-def _find_executable_or_die(executable: str) -> str:
+def _find_executable_or_die(
+    executable_name: str, executable_path: Optional[str] = None
+) -> str:
   """Finds executable and resolves symlinks or raises RuntimeError.
 
   Resolving symlinks is sometimes necessary for finding system headers.
 
   Args:
-    executable: The name of the executable that we want to find.
+    executable_name: The name of the executable that we want to find.
+    executable_path: If not None, the path to the executable.
 
   Returns:
-    The path to the executable we are looking for.
+    The path to the executable we are looking for, after symlinks are resolved.
   Raises:
     RuntimeError: if path to the executable cannot be found.
   """
-  resolved_path_to_exe = _find_executable(executable)
+  if executable_path:
+    return str(pathlib.Path(executable_path).resolve(strict=True))
+  resolved_path_to_exe = _find_executable(executable_name)
   if resolved_path_to_exe is None:
     raise RuntimeError(
-        f"Could not find executable `{executable}`! "
+        f"Could not find executable `{executable_name}`! "
         "Please change your $PATH or pass the path directly like"
-        f"`--{executable}_path=path/to/executable."
+        f"`--{executable_name}_path=path/to/executable."
     )
-  logging.info("Found path to %s at %s", executable, resolved_path_to_exe)
+  logging.info("Found path to %s at %s", executable_name, resolved_path_to_exe)
 
   return resolved_path_to_exe
 
@@ -236,7 +241,7 @@ def get_relevant_paths_and_versions(self, config: "XLAConfigOptions"):
       self.ld_library_path = os.environ.get("LD_LIBRARY_PATH", None)
 
     if config.host_compiler == HostCompiler.CLANG:
-      self.clang_path = self.clang_path or _find_executable_or_die("clang")
+      self.clang_path = _find_executable_or_die("clang", self.clang_path)
       self.clang_major_version = (
           self.clang_major_version or _get_clang_major_version(self.clang_path)
       )
@@ -247,11 +252,11 @@ def get_relevant_paths_and_versions(self, config: "XLAConfigOptions"):
       # directly.
       self.lld_path = self.lld_path or shutil.which("ld.lld")
     elif config.host_compiler == HostCompiler.GCC:
-      self.gcc_path = self.gcc_path or _find_executable_or_die("gcc")
+      self.gcc_path = _find_executable_or_die("gcc", self.gcc_path)
 
     if config.backend == Backend.CUDA:
       if config.cuda_compiler == CudaCompiler.CLANG:
-        self.clang_path = self.clang_path or _find_executable_or_die("clang")
+        self.clang_path = _find_executable_or_die("clang", self.clang_path)
 
       if not self.cuda_compute_capabilities:
         self.cuda_compute_capabilities = _get_cuda_compute_capabilities_or_die()

build_tools/configure/configure_test.py

@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
+import os
+
 from absl.testing import absltest
 
 from xla.build_tools import test_utils
@@ -55,7 +57,11 @@ def setUpClass(cls):
       cls.clang_bazelrc_lines = [line.strip() for line in f.readlines()]
 
     with (testdata / "gcc.bazelrc").open() as f:
-      cls.gcc_bazelrc_lines = [line.strip() for line in f.readlines()]
+      resolved_gcc_path = os.path.realpath(_GCC_PATH)
+      cls.gcc_bazelrc_lines = [
+          line.strip().replace(_GCC_PATH, resolved_gcc_path)
+          for line in f.readlines()
+      ]
 
     with (testdata / "cuda_clang.bazelrc").open() as f:
       cls.cuda_clang_bazelrc_lines = [line.strip() for line in f.readlines()]
@@ -64,7 +70,11 @@ def setUpClass(cls):
       cls.nvcc_clang_bazelrc_lines = [line.strip() for line in f.readlines()]
 
     with (testdata / "nvcc_gcc.bazelrc").open() as f:
-      cls.nvcc_gcc_bazelrc_lines = [line.strip() for line in f.readlines()]
+      resolved_gcc_path = os.path.realpath(_GCC_PATH)
+      cls.nvcc_gcc_bazelrc_lines = [
+          line.strip().replace(_GCC_PATH, resolved_gcc_path)
+          for line in f.readlines()
+      ]
 
   def test_clang_bazelrc(self):
     config = XLAConfigOptions(