Issue #21085: add configure check for siginfo_t.si_band

Patch by Masayuki Yamamoto, reviewed and rebased by Erik Bray.

This is a first step on the long road toward resupporting Cygwin, which does
not provide siginfo_t.si_band.

Misc/ACKS

@@ -1671,6 +1671,7 @@ Florent Xicluna
 Arnon Yaari
 Alakshendra Yadav
 Hirokazu Yamamoto
+Masayuki Yamamoto
 Ka-Ping Yee
 Chi Hsuan Yen
 Jason Yeo

Misc/NEWS

@@ -173,6 +173,9 @@ Windows
 Build
 -----
 
+- Issue #21085: Add configure check for siginfo_t.si_band, which Cygwin does
+  not provide.  Patch by Masayuki Yamamoto with review and rebase by Erik Bray.
+
 - Issue #28258: Fixed build with Estonian locale (python-config and distclean
   targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.
 

Modules/signalmodule.c

@@ -957,7 +957,11 @@ fill_siginfo(siginfo_t *si)
     PyStructSequence_SET_ITEM(result, 4, _PyLong_FromUid(si->si_uid));
     PyStructSequence_SET_ITEM(result, 5,
                                 PyLong_FromLong((long)(si->si_status)));
+#ifdef HAVE_SIGINFO_T_SI_BAND
     PyStructSequence_SET_ITEM(result, 6, PyLong_FromLong(si->si_band));
+#else
+    PyStructSequence_SET_ITEM(result, 6, PyLong_FromLong(0L));
+#endif
     if (PyErr_Occurred()) {
         Py_DECREF(result);
         return NULL;

configure

@@ -13087,6 +13087,18 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+fi
+
+# Issue #21085: In Cygwin, siginfo_t does not have si_band field.
+ac_fn_c_check_member "$LINENO" "siginfo_t" "si_band" "ac_cv_member_siginfo_t_si_band" "#include <signal.h>
+"
+if test "x$ac_cv_member_siginfo_t_si_band" = xyes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_SIGINFO_T_SI_BAND 1
+_ACEOF
+
+
 fi
 
 

configure.ac

@@ -3907,6 +3907,8 @@ AC_CHECK_MEMBERS([struct passwd.pw_gecos, struct passwd.pw_passwd], [], [], [[
   #include <sys/types.h>
   #include <pwd.h>
 ]])
++# Issue #21085: In Cygwin, siginfo_t does not have si_band field.
++AC_CHECK_MEMBERS([siginfo_t.si_band], [], [], [[#include <signal.h>]])
 
 AC_MSG_CHECKING(for time.h that defines altzone)
 AC_CACHE_VAL(ac_cv_header_time_altzone,[

pyconfig.h.in

@@ -856,6 +856,9 @@
 /* Define to 1 if you have the `sigaltstack' function. */
 #undef HAVE_SIGALTSTACK
 
+/* Define to 1 if `si_band' is a member of `siginfo_t'. */
+#undef HAVE_SIGINFO_T_SI_BAND
+
 /* Define to 1 if you have the `siginterrupt' function. */
 #undef HAVE_SIGINTERRUPT