[configure] Detect HAVE_GLOB_PERIOD, and use it

Overriding GLOB_PERIOD as 0 isn't quite right.  It doesn't work in both
Python and C++.

configure

@@ -309,9 +309,11 @@ echo_shell_vars() {
     echo 'HAVE_READLINE='
     echo 'READLINE_DIR='
   fi
+  echo
 
   echo "PREFIX=$FLAG_prefix"
   echo "DATAROOTDIR=$FLAG_datarootdir"
+  echo
 
   if cc_quiet build/detect-cc.c -Wl,--gc-sections; then
     echo 'STRIP_FLAGS=--gc-sections'
@@ -368,6 +370,20 @@ check_sizeof() {
 }
 
 detect_c_language() {
+  # Exported by pyext/libc.c
+  if test "$have_fnm_extmatch" = 1; then
+    echo '#define HAVE_FNM_EXTMATCH 1'
+  else
+    echo '#define HAVE_FNM_EXTMATCH 0'
+  fi
+
+  if test "$have_glob_period" = 1; then
+    echo '#define HAVE_GLOB_PERIOD 1'
+  else
+    echo '#define HAVE_GLOB_PERIOD 0'
+  fi
+  echo
+
   # This is the equivalent of AC_CHECK_SIZEOF(int, 4)
   check_sizeof SIZEOF_INT 'int' 4
   check_sizeof SIZEOF_LONG 'long' 4
@@ -465,20 +481,18 @@ echo_cpp() {
     echo '/* #undef HAVE_SYSTEMTAP_SDT */'
   fi
 
+  echo
+
   if test "$have_fnm_extmatch" = 1; then
-    echo '/* libc defines FNM_EXTMATCH */'
+    echo '#define HAVE_FNM_EXTMATCH 1'
   else
-    # INVALID value that we can detect in code
-    # e.g. musl libc does not support this, but glibc does
-    echo '#define FNM_EXTMATCH 0'
+    echo '#define HAVE_FNM_EXTMATCH 0'
   fi
 
   if test "$have_glob_period" = 1; then
-    echo '/* libc defines GLOB_PERIOD */'
+    echo '#define HAVE_GLOB_PERIOD 1'
   else
-    # INVALID value that we can detect in code
-    # e.g. Android does not support this, but glibc and musl libc do
-    echo '#define GLOB_PERIOD 0'
+    echo '#define HAVE_GLOB_PERIOD 0'
   fi
 
   # Used by cpp/core.cc

core/state.py

@@ -36,7 +36,7 @@
                          NewDict)
 from pylib import os_path
 
-from libc import GLOB_PERIOD
+from libc import HAVE_GLOB_PERIOD
 import posix_ as posix
 
 from typing import Tuple, List, Dict, Optional, Any, cast, TYPE_CHECKING
@@ -347,7 +347,7 @@ def _SetOptionNum(opt_name):
 
 def _MaybeWarnDotglob():
     # type: () -> None
-    if GLOB_PERIOD == 0:  # invalid value that means it wasn't detected
+    if HAVE_GLOB_PERIOD == 0:
         # GNU libc and musl libc have GLOB_PERIOD, but Android doesn't
         print_stderr(
             "osh warning: GLOB_PERIOD wasn't found in libc, so 'shopt -s dotglob' won't work")

osh/glob_.py

@@ -16,7 +16,7 @@
 from mycpp import mylib
 from mycpp.mylib import log, print_stderr
 
-from libc import GLOB_PERIOD
+from libc import GLOB_PERIOD, HAVE_GLOB_PERIOD
 
 from typing import List, Tuple, cast, TYPE_CHECKING
 if TYPE_CHECKING:
@@ -416,7 +416,7 @@ def _Glob(self, arg, out):
         # type: (str, List[str]) -> int
         try:
             flags = 0
-            if self.exec_opts.dotglob():
+            if self.exec_opts.dotglob() and HAVE_GLOB_PERIOD:
                 flags |= GLOB_PERIOD
             results = libc.glob(arg, flags)
         except RuntimeError as e:

pyext/libc.c

@@ -21,6 +21,8 @@
 
 #include <Python.h>
 
+#include "_build/detected-config.h"
+
 // Log messages to stderr.
 static void debug(const char* fmt, ...) {
 #ifdef LIBC_VERBOSE
@@ -410,8 +412,12 @@ void initlibc(void) {
 
   module = Py_InitModule("libc", methods);
   if (module != NULL) {
+      // ./configure values
+      PyModule_AddIntConstant(module, "HAVE_GLOB_PERIOD", HAVE_GLOB_PERIOD);
+      PyModule_AddIntConstant(module, "HAVE_FNM_EXTMATCH", HAVE_FNM_EXTMATCH);
+
+      // Actual libc values
       PyModule_AddIntConstant(module, "GLOB_PERIOD", GLOB_PERIOD);
-      PyModule_AddIntConstant(module, "FNM_EXTMATCH", FNM_EXTMATCH);
       PyModule_AddIntConstant(module, "FNM_CASEFOLD", FNM_CASEFOLD);
       PyModule_AddIntConstant(module, "REG_ICASE", REG_ICASE);
       PyModule_AddIntConstant(module, "REG_NEWLINE", REG_NEWLINE);

pyext/libc.pyi

@@ -1,5 +1,10 @@
 from typing import List, Optional, Tuple
 
+# generated by ./configure
+HAVE_GLOB_PERIOD: int
+HAVE_FNM_EXTMATCH: int
+
+# libc values
 FNM_CASEFOLD: int
 GLOB_PERIOD: int
 REG_ICASE: int

pyext/libc_test.py

@@ -22,7 +22,8 @@ class LibcTest(unittest.TestCase):
 
   def testConstants(self):
       print('GLOB_PERIOD %d' % libc.GLOB_PERIOD)
-      print('FNM_EXTMATCH %d' % libc.FNM_EXTMATCH)
+      print('HAVE_GLOB_PERIOD %d' % libc.HAVE_GLOB_PERIOD)
+      print('HAVE_FNM_EXTMATCH %d' % libc.HAVE_FNM_EXTMATCH)
 
   def testFnmatch(self):
 

pyext/setup_libc.py

@@ -3,6 +3,8 @@
 
 module = Extension('libc',
                     sources = ['pyext/libc.c'],
+                    # for #include "_build/detected-config.h"
+                    extra_compile_args = ['-I', '.'],
                     undef_macros = ['NDEBUG'])
 
 setup(name = 'libc',