Fix: Accept lists in gen_preprocess_options for TOML compatibility

docs/conf.py

@@ -194,12 +194,7 @@
 
 # Allow linking objects on other Sphinx sites seamlessly:
 intersphinx_mapping.update(
-    # python=('https://docs.python.org/3', None),
-    python=('https://docs.python.org/3.11', None),
-    # ^-- Python 3.11 is required because it still contains `distutils`.
-    #     Just leaving it as `3` would imply 3.12+, but that causes an
-    #     error with the cross references to distutils functions.
-    #     Inventory cache may cause errors, deleting it solves the problem.
+    python=('https://docs.python.org/3', None),
 )
 
 # Add support for the unreleased "next-version" change notes

docs/userguide/extension.rst

@@ -293,7 +293,7 @@ A few important points for writing revision control file finders:
   inform the user of the missing program(s).
 
 
-.. _distutils: https://docs.python.org/3.9/library/distutils.html
+.. _distutils: https://setuptools.pypa.io/en/latest/deprecated/distutils/index.html
 
 
 Final Remarks

setuptools/_distutils/compilers/C/base.py

@@ -1327,6 +1327,9 @@ def gen_preprocess_options(
     # and therefore common to all CCompiler classes.
     pp_opts = []
     for macro in macros:
+        # Convert lists to tuples to support TOML format which uses arrays
+        if isinstance(macro, list):
+            macro = tuple(macro)
         if not (isinstance(macro, tuple) and 1 <= len(macro) <= 2):
             raise TypeError(
                 f"bad macro definition '{macro}': "

setuptools/_distutils/compilers/C/tests/test_base.py

@@ -81,3 +81,45 @@ def test_include_dirs_after_multiple_compile_calls(c_file):
     assert compiler.include_dirs == [python]
     compiler.compile([c_file])
     assert compiler.include_dirs == [python]
+
+
+def test_gen_preprocess_options_with_lists():
+    """
+    Test that gen_preprocess_options accepts lists (from TOML format)
+    and converts them to tuples. Regression test for issue #4810.
+    """
+    from ..base import gen_preprocess_options
+
+    # Test with lists (as provided by TOML/pyproject.toml)
+    macros_as_lists = [
+        ["MACRO1"],  # single-element list
+        ["MACRO2", "value"],  # two-element list
+        ["MACRO3", None],  # list with None
+    ]
+
+    result = gen_preprocess_options(macros_as_lists, [])
+    assert "-UMACRO1" in result
+    assert "-DMACRO2=value" in result
+    assert "-DMACRO3" in result
+
+    # Test with tuples (original format should still work)
+    macros_as_tuples = [
+        ("MACRO4",),
+        ("MACRO5", "value"),
+        ("MACRO6", None),
+    ]
+
+    result = gen_preprocess_options(macros_as_tuples, [])
+    assert "-UMACRO4" in result
+    assert "-DMACRO5=value" in result
+    assert "-DMACRO6" in result
+
+    # Test mixed lists and tuples
+    mixed_macros = [
+        ["MACRO_A"],
+        ("MACRO_B", "value"),
+    ]
+
+    result = gen_preprocess_options(mixed_macros, [])
+    assert "-UMACRO_A" in result
+    assert "-DMACRO_B=value" in result