bpo-45221: Fix handling of LDFLAGS and CPPFLAGS options in setup.py (GH-29031)

1 files changed, 12 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index 24365ef..5428cbd 100644
--- a/setup.py
+++ b/setup.py
@@ -801,6 +801,18 @@ class PyBuildExt(build_ext):
             if env_val:
                 parser = argparse.ArgumentParser()
                 parser.add_argument(arg_name, dest="dirs", action="append")
+
+                # To prevent argparse from raising an exception about any
+                # options in env_val that it mistakes for known option, we
+                # strip out all double dashes and any dashes followed by a
+                # character that is not for the option we are dealing with.
+                #
+                # Please note that order of the regex is important!  We must
+                # strip out double-dashes first so that we don't end up with
+                # substituting "--Long" to "-Long" and thus lead to "ong" being
+                # used for a library directory.
+                env_val = re.sub(r'(^|\s+)-(-|(?!%s))' % arg_name[1],
+                                 ' ', env_val)
                 options, _ = parser.parse_known_args(env_val.split())
                 if options.dirs:
                     for directory in reversed(options.dirs):