Add --with-tzpath to autoconf

This is configurable only on POSIX systems at the moment and TZPATH is
initialized to an empty string on Windows.

Lib/sysconfig.py

@@ -546,6 +546,7 @@ def get_config_vars(*args):
 
         if os.name == 'nt':
             _init_non_posix(_CONFIG_VARS)
+            _CONFIG_VARS['TZPATH'] = ''
         if os.name == 'posix':
             _init_posix(_CONFIG_VARS)
         # For backward compatibility, see issue19555

Lib/zoneinfo/_tzpath.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import sysconfig
 
 
 def reset_tzpath(to=None):
@@ -19,17 +20,10 @@ def reset_tzpath(to=None):
         env_var = os.environ.get("PYTHONTZPATH", None)
         if env_var is not None:
             base_tzpath = _parse_python_tzpath(env_var)
-        elif sys.platform != "win32":
-            base_tzpath = [
-                "/usr/share/zoneinfo",
-                "/usr/lib/zoneinfo",
-                "/usr/share/lib/zoneinfo",
-                "/etc/zoneinfo",
-            ]
-
-            base_tzpath.sort(key=lambda x: not os.path.exists(x))
         else:
-            base_tzpath = ()
+            base_tzpath = _parse_python_tzpath(
+                sysconfig.get_config_var("TZPATH")
+            )
 
     TZPATH = tuple(base_tzpath)
 

Makefile.pre.in

@@ -197,6 +197,9 @@ OPENSSL_INCLUDES=@OPENSSL_INCLUDES@
 OPENSSL_LIBS=@OPENSSL_LIBS@
 OPENSSL_LDFLAGS=@OPENSSL_LDFLAGS@
 
+# Default zoneinfo.TZPATH. Added here to expose it in sysconfig.get_config_var
+TZPATH=@TZPATH@
+
 # Modes for directories, executables and data files created by the
 # install process.  Default to user-only-writable for all file types.
 DIRMODE=	755

configure

@@ -658,6 +658,7 @@ LIBFFI_INCLUDEDIR
 PKG_CONFIG_LIBDIR
 PKG_CONFIG_PATH
 PKG_CONFIG
+TZPATH
 SHLIBS
 CFLAGSFORSHARED
 LINKFORSHARED
@@ -819,6 +820,7 @@ with_assertions
 enable_optimizations
 with_lto
 with_hash_algorithm
+with_tzpath
 with_address_sanitizer
 with_memory_sanitizer
 with_undefined_behavior_sanitizer
@@ -1524,6 +1526,9 @@ Optional Packages:
   --with-hash-algorithm=[fnv|siphash24]
                           select hash algorithm for use in Python/pyhash.c
                           (default is SipHash24)
+  --with-tzpath=<list of absolute paths separated by pathsep>
+                           Select the default time zone search path for zoneinfo.TZPATH
+
   --with-address-sanitizer
                           enable AddressSanitizer memory error detector,
                           'asan' (default is no)
@@ -10150,6 +10155,47 @@ $as_echo "default" >&6; }
 fi
 
 
+validate_tzpath() {
+    # Checks that each element of hte path is an absolute path
+    if test -z "$1"; then
+        # Empty string is allowed: it indicates no system TZPATH
+        return 0
+    fi
+
+    # Bad paths are those that don't start with /
+        if ( echo $1 | grep -qE '(^|:)([^/]|$)' ); then
+        as_fn_error $? "--with-tzpath must contain only absolute paths, not $1" "$LINENO" 5
+        return 1;
+    fi
+}
+
+TZPATH="/usr/share/zoneinfo:/usr/lib/zoneinfo:/usr/share/lib/zoneinfo:/etc/zoneinfo"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-tzpath" >&5
+$as_echo_n "checking for --with-tzpath... " >&6; }
+
+# Check whether --with-tzpath was given.
+if test "${with_tzpath+set}" = set; then :
+  withval=$with_tzpath;
+case "$withval" in
+    yes)
+        as_fn_error $? "--with-tzpath requires a value" "$LINENO" 5
+        ;;
+    *)
+        validate_tzpath "$withval"
+        TZPATH="$withval"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: \"$withval\"" >&5
+$as_echo "\"$withval\"" >&6; }
+        ;;
+esac
+
+else
+  validate_tzpath "$TZPATH"
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: \"$TZPATH\"" >&5
+$as_echo "\"$TZPATH\"" >&6; }
+fi
+
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-address-sanitizer" >&5
 $as_echo_n "checking for --with-address-sanitizer... " >&6; }
 

configure.ac

@@ -2946,6 +2946,42 @@ esac
 ],
 [AC_MSG_RESULT(default)])
 
+validate_tzpath() {
+    # Checks that each element of hte path is an absolute path
+    if test -z "$1"; then
+        # Empty string is allowed: it indicates no system TZPATH
+        return 0
+    fi
+
+    # Bad paths are those that don't start with /
+    dnl quadrigraphs "@<:@" and "@:>@" produce "[" and "]" in the output
+    if ( echo $1 | grep -qE '(^|:)(@<:@^/@:>@|$)' ); then
+        AC_MSG_ERROR([--with-tzpath must contain only absolute paths, not $1])
+        return 1;
+    fi
+}
+
+TZPATH="/usr/share/zoneinfo:/usr/lib/zoneinfo:/usr/share/lib/zoneinfo:/etc/zoneinfo"
+AC_MSG_CHECKING(for --with-tzpath)
+AC_ARG_WITH(tzpath,
+            AS_HELP_STRING([--with-tzpath=<list of absolute paths separated by pathsep>]
+                           [Select the default time zone search path for zoneinfo.TZPATH]),
+[
+case "$withval" in
+    yes)
+        AC_MSG_ERROR([--with-tzpath requires a value])
+        ;;
+    *)
+        validate_tzpath "$withval"
+        TZPATH="$withval"
+        AC_MSG_RESULT("$withval")
+        ;;
+esac
+],
+[validate_tzpath "$TZPATH"
+ AC_MSG_RESULT("$TZPATH")])
+AC_SUBST(TZPATH)
+
 AC_MSG_CHECKING(for --with-address-sanitizer)
 AC_ARG_WITH(address_sanitizer,
             AS_HELP_STRING([--with-address-sanitizer],

setup.py

@@ -304,6 +304,17 @@ def find_library_file(compiler, libname, std_dirs, paths):
     else:
         assert False, "Internal error: Path not found in std_dirs or paths"
 
+def validate_tzpath():
+    base_tzpath = sysconfig.get_config_var('TZPATH')
+    if not base_tzpath:
+        return
+
+    tzpaths = base_tzpath.split(os.pathsep)
+    bad_paths = [tzpath for tzpath in tzpaths if not os.path.isabs(tzpath)]
+    if bad_paths:
+        raise ValueError('TZPATH must contain only absolute paths, '
+                         + f'found:\n{tzpaths!r}\nwith invalid paths:\n'
+                         + f'{bad_paths!r}')
 
 def find_module_file(module, dirlist):
     """Find a module in a set of possible folders. If it is not found
@@ -2451,6 +2462,7 @@ class DummyProcess:
         ProcessPoolExecutor = None
 
     sys.modules['concurrent.futures.process'] = DummyProcess
+    validate_tzpath()
 
     # turn off warnings when deprecated modules are imported
     import warnings