On all the systems I could get hold of (Solaris, ReliantUNIX, BS2000, SINIX),

SHM_R was always 0400, never 0x400. My assumption is that is usually (always) is.
Feel free to change it to an OS test like this (if your OS differs):
case `uname -s` in
  SunOS | POSIX-BC | SINIX-* | ReliantUNIX-* ) # BS2000
    AC_DEFINE(SHM_R, 0400, [ ])
    AC_DEFINE(SHM_W, 0200, [ ])
    ;;
  *)
    AC_DEFINE(SHM_R, 0x400, [ ])
    AC_DEFINE(SHM_W, 0x200, [ ])
    ;;
esac


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84953 13f79535-47bb-0310-9956-ffa450edef68