I find that it is necessary to #define _POSIX to get a full set of POSIX signal names defined in mingw's signal.h. I'm slightly surprised to find this is not implemented in gnulib: is there a reason?
If not, it would be straightforward to add
#ifdef __MINGW32__
#define _POSIX
#endif
before the #include of the system signal.h
# @INCLUDE_NEXT@ @NEXT_SIGNAL_H@
in signal.in.h.
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