/usr/lib/xemacs-21.4.24/x86_64-linux-gnu/include/s/cxux7.h is in xemacs21-bin 21.4.24-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | /* Synched up with: FSF 19.31. */
/* Define this symbol if you are running CX/UX 7.0 or later (7.0 introduced
* support for ELF files, and while we still build emacs in COFF format, the
* way it is linked is different for 7.0).
*/
#define USING_CX_UX_7
#include "cxux.h"
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