Add configure test for NSIG, _NSIG or __NSIG.

This is better than just defining NSIG in sudo_compat.h if it is
not defined since signal.h may not have been included.

config.h.in

@@ -155,6 +155,10 @@
    don't. */
 #undef HAVE_DECL_LLONG_MIN
 
+/* Define to 1 if you have the declaration of 'NSIG', and to 0 if you don't.
+   */
+#undef HAVE_DECL_NSIG
+
 /* Define to 1 if you have the declaration of 'PATH_MAX', and to 0 if you
    don't. */
 #undef HAVE_DECL_PATH_MAX
@@ -231,6 +235,10 @@
    don't. */
 #undef HAVE_DECL__INNETGR
 
+/* Define to 1 if you have the declaration of '_NSIG', and to 0 if you don't.
+   */
+#undef HAVE_DECL__NSIG
+
 /* Define to 1 if you have the declaration of '_POSIX_PATH_MAX', and to 0 if
    you don't. */
 #undef HAVE_DECL__POSIX_PATH_MAX
@@ -243,6 +251,10 @@
    don't. */
 #undef HAVE_DECL__SYS_SIGNAME
 
+/* Define to 1 if you have the declaration of '__NSIG', and to 0 if you don't.
+   */
+#undef HAVE_DECL___NSIG
+
 /* Define to 1 if you have the 'devname' function. */
 #undef HAVE_DEVNAME
 

configure

@@ -27654,6 +27654,65 @@ case "$enable_zlib" in
 	;;
 esac
 
+ac_fn_check_decl "$LINENO" "NSIG" "ac_cv_have_decl_NSIG" "
+$ac_includes_default
+#include <signal.h>
+
+" "$ac_c_undeclared_builtin_options" "CFLAGS"
+if test "x$ac_cv_have_decl_NSIG" = xyes
+then :
+  ac_have_decl=1
+else case e in #(
+  e) ac_have_decl=0 ;;
+esac
+fi
+printf "%s\n" "#define HAVE_DECL_NSIG $ac_have_decl" >>confdefs.h
+if test $ac_have_decl = 1
+then :
+
+else case e in #(
+  e)
+    ac_fn_check_decl "$LINENO" "_NSIG" "ac_cv_have_decl__NSIG" "
+$ac_includes_default
+#include <signal.h>
+
+" "$ac_c_undeclared_builtin_options" "CFLAGS"
+if test "x$ac_cv_have_decl__NSIG" = xyes
+then :
+  ac_have_decl=1
+else case e in #(
+  e) ac_have_decl=0 ;;
+esac
+fi
+printf "%s\n" "#define HAVE_DECL__NSIG $ac_have_decl" >>confdefs.h
+if test $ac_have_decl = 1
+then :
+
+else case e in #(
+  e)
+	ac_fn_check_decl "$LINENO" "__NSIG" "ac_cv_have_decl___NSIG" "
+$ac_includes_default
+#include <signal.h>
+
+" "$ac_c_undeclared_builtin_options" "CFLAGS"
+if test "x$ac_cv_have_decl___NSIG" = xyes
+then :
+  ac_have_decl=1
+else case e in #(
+  e) ac_have_decl=0 ;;
+esac
+fi
+printf "%s\n" "#define HAVE_DECL___NSIG $ac_have_decl" >>confdefs.h
+
+     ;;
+esac
+fi
+
+ ;;
+esac
+fi
+
+
 ac_fn_check_decl "$LINENO" "errno" "ac_cv_have_decl_errno" "
 $ac_includes_default
 #include <errno.h>

configure.ac

@@ -3282,6 +3282,24 @@ case "$enable_zlib" in
 	;;
 esac
 
+dnl
+dnl Check for NSIG, _NSIG or __NSIG declarations in signal.h
+dnl
+AC_CHECK_DECLS([NSIG], [], [
+    AC_CHECK_DECLS([_NSIG], [], [
+	AC_CHECK_DECLS([__NSIG], [], [], [
+AC_INCLUDES_DEFAULT
+#include <signal.h>
+	])
+    ], [
+AC_INCLUDES_DEFAULT
+#include <signal.h>
+    ])
+], [
+AC_INCLUDES_DEFAULT
+#include <signal.h>
+])
+
 dnl
 dnl Check for errno declaration in errno.h
 dnl

include/sudo_compat.h

@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: ISC
  *
- * Copyright (c) 1996, 1998-2005, 2008, 2009-2022
+ * Copyright (c) 1996, 1998-2005, 2008, 2009-2023
  *	Todd C. Miller <Todd.Miller@sudo.ws>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -205,10 +205,10 @@ extern int errno;
 #endif /* !HAVE_DECL_ERRNO */
 
 /* Not all systems define NSIG in signal.h */
-#if !defined(NSIG)
+#if !defined(HAVE_DECL_NSIG) || !HAVE_DECL_NSIG
-# if defined(_NSIG)
+# if defined(HAVE_DECL__NSIG) && HAVE_DECL__NSIG
 #  define NSIG _NSIG
-# elif defined(__NSIG)
+# elif defined(HAVE_DECL___NSIG) && HAVE_DECL___NSIG
 #  define NSIG __NSIG
 # else
 #  define NSIG 64