From 929323f49c0cbc4c3d0147cc190f9cd34ece6e98 Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Sat, 13 Aug 2022 10:13:26 -0400
Subject: [PATCH] Deprecate behavior in _mangle_base. Ref pypa/distutils#169.

---
 distutils/ccompiler.py | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/distutils/ccompiler.py b/distutils/ccompiler.py
index 8c9b1d48..c8d3b24b 100644
--- a/distutils/ccompiler.py
+++ b/distutils/ccompiler.py
@@ -6,6 +6,8 @@
 import sys
 import os
 import re
+import warnings
+
 from distutils.errors import (
     CompileError,
     LinkError,
@@ -943,7 +945,16 @@ def _mangle_base(base):
         # Chop off the drive
         no_drive = os.path.splitdrive(base)[1]
         # If abs, chop off leading /
-        return no_drive[os.path.isabs(no_drive) :]
+        rel = no_drive[os.path.isabs(no_drive) :]
+        if rel != base:
+            msg = (
+                f"Absolute path {base!r} is being replaced with a "
+                f"relative path {rel!r} for outputs. This behavior is "
+                "deprecated. If this behavior is desired, please "
+                "comment in pypa/distutils#169."
+            )
+            warnings.warn(msg, DeprecationWarning)
+        return rel
 
     def shared_object_filename(self, basename, strip_dir=0, output_dir=''):
         assert output_dir is not None