cpython: fix ctypes.util.find_library

pkgs/development/interpreters/python/cpython/3.7/find_library.patch

@@ -0,0 +1,105 @@
+From 9b5a023a5dc3127da15253f7acad71019395ebe1 Mon Sep 17 00:00:00 2001
+From: Pablo Galindo <Pablogsal@gmail.com>
+Date: Thu, 8 Oct 2020 19:50:37 +0100
+Subject: [PATCH] [3.7] bpo-41976: Fix the fallback to gcc of
+ ctypes.util.find_library when using gcc>9 (GH-22598). (GH-22601)
+
+(cherry picked from commit 27ac19cca2c639caaf6fedf3632fe6beb265f24f)
+
+Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
+---
+ Lib/ctypes/test/test_find.py                  | 12 ++++++-
+ Lib/ctypes/util.py                            | 32 +++++++++++++++----
+ .../2020-10-08-18-22-28.bpo-41976.Svm0wb.rst  |  3 ++
+ 3 files changed, 39 insertions(+), 8 deletions(-)
+ create mode 100644 Misc/NEWS.d/next/Library/2020-10-08-18-22-28.bpo-41976.Svm0wb.rst
+
+diff --git a/Lib/ctypes/test/test_find.py b/Lib/ctypes/test/test_find.py
+index b99fdcba7b28f..92ac1840ad7d4 100644
+--- a/Lib/ctypes/test/test_find.py
++++ b/Lib/ctypes/test/test_find.py
+@@ -1,4 +1,5 @@
+ import unittest
++import unittest.mock
+ import os.path
+ import sys
+ import test.support
+@@ -72,7 +73,7 @@ def test_shell_injection(self):
+ 
+ @unittest.skipUnless(sys.platform.startswith('linux'),
+                      'Test only valid for Linux')
+-class LibPathFindTest(unittest.TestCase):
++class FindLibraryLinux(unittest.TestCase):
+     def test_find_on_libpath(self):
+         import subprocess
+         import tempfile
+@@ -111,6 +112,15 @@ def test_find_on_libpath(self):
+                 # LD_LIBRARY_PATH)
+                 self.assertEqual(find_library(libname), 'lib%s.so' % libname)
+ 
++    def test_find_library_with_gcc(self):
++        with unittest.mock.patch("ctypes.util._findSoname_ldconfig", lambda *args: None):
++            self.assertNotEqual(find_library('c'), None)
++
++    def test_find_library_with_ld(self):
++        with unittest.mock.patch("ctypes.util._findSoname_ldconfig", lambda *args: None), \
++             unittest.mock.patch("ctypes.util._findLib_gcc", lambda *args: None):
++            self.assertNotEqual(find_library('c'), None)
++
+ 
+ if __name__ == "__main__":
+     unittest.main()
+diff --git a/Lib/ctypes/util.py b/Lib/ctypes/util.py
+index 97973bce001d9..0c2510e1619c8 100644
+--- a/Lib/ctypes/util.py
++++ b/Lib/ctypes/util.py
+@@ -93,6 +93,12 @@ def find_library(name):
+     # Andreas Degert's find functions, using gcc, /sbin/ldconfig, objdump
+     import re, tempfile
+ 
++    def _is_elf(filename):
++        "Return True if the given file is an ELF file"
++        elf_header = b'\x7fELF'
++        with open(filename, 'br') as thefile:
++            return thefile.read(4) == elf_header
++
+     def _findLib_gcc(name):
+         # Run GCC's linker with the -t (aka --trace) option and examine the
+         # library name it prints out. The GCC command will fail because we
+@@ -299,17 +312,22 @@ def _findLib_ld(name):
+                                      stderr=subprocess.PIPE,
+                                      universal_newlines=True)
+                 out, _ = p.communicate()
+-                res = re.search(expr, os.fsdecode(out))
+-                if res:
+-                    result = res.group(0)
+-            except Exception as e:
++                res = re.findall(expr, os.fsdecode(out))
++                for file in res:
++                    # Check if the given file is an elf file: gcc can report
++                    # some files that are linker scripts and not actual
++                    # shared objects. See bpo-41976 for more details
++                    if not _is_elf(file):
++                        continue
++                    return os.fsdecode(file)
++            except Exception:
+                 pass  # result will be None
+             return result
+ 
+         def find_library(name):
+             # See issue #9998
+             return _findSoname_ldconfig(name) or \
+-                   _get_soname(_findLib_gcc(name) or _findLib_ld(name))
++                   _get_soname(_findLib_gcc(name)) or _get_soname(_findLib_ld(name))
+ 
+ ################################################################
+ # test code
+diff --git a/Misc/NEWS.d/next/Library/2020-10-08-18-22-28.bpo-41976.Svm0wb.rst b/Misc/NEWS.d/next/Library/2020-10-08-18-22-28.bpo-41976.Svm0wb.rst
+new file mode 100644
+index 0000000000000..c8b3fc771845e
+--- /dev/null
++++ b/Misc/NEWS.d/next/Library/2020-10-08-18-22-28.bpo-41976.Svm0wb.rst
+@@ -0,0 +1,3 @@
++Fixed a bug that was causing :func:`ctypes.util.find_library` to return
++``None`` when triying to locate a library in an environment when gcc>=9 is
++available and ``ldconfig`` is not. Patch by Pablo Galindo

pkgs/development/interpreters/python/cpython/default.nix

@@ -165,6 +165,9 @@ in with passthru; stdenv.mkDerivation {
   ] ++ [
     # LDSHARED now uses $CC instead of gcc. Fixes cross-compilation of extension modules.
     ./3.8/0001-On-all-posix-systems-not-just-Darwin-set-LDSHARED-if.patch
+  ] ++ optionals (isPy37 || isPy38) [
+    # Backport a fix for ctypes.util.find_library.
+    ./3.7/find_library.patch
   ];
 
   postPatch = ''