Error: unknown type name ‘pthread_attr_t’ in signal.h

[Jeffrey Walton]

Hi Everyone,

I'm trying to build Emacs on Cygwin. I use the platform as a test bed
because of Newlib. Emacs is failing with:

gcc -DHAVE_CONFIG_H -I. -I../lib -I../src -I../src
-I/usr/local/include -DNDEBUG -pthread -D_XOPEN_SOURCE=600    -m64 -MT
close-stream.o -MD -MP -MF .deps/close-stream.Tpo -c -o close-stream.o
close-stream.c
In file included from /usr/include/sys/signal.h:22:0,
                 from /usr/include/signal.h:6,
                 from ./signal.h:52,
                 from ./sys/select.h:107,
                 from /usr/include/sys/time.h:47,
                 from ./sys/time.h:39,
                 from ./sys/select.h:86,
                 from /usr/include/sys/types.h:68,
                 from ./sys/types.h:28,
                 from ./fcntl.h:50,
                 from binary-io.h:23,
                 from binary-io.c:3:
/usr/include/cygwin/signal.h:175:3: error: unknown type name ‘pthread_attr_t’
   pthread_attr_t *sigev_notify_attributes; /* notification attributes */
   ^~~~~~~~~~~~~~

Examining /usr/include/cygwin/signal.h around 175, I see:

typedef struct sigevent
{
  sigval_t sigev_value;                 /* signal value */
  int sigev_signo;                      /* signal number */
  int sigev_notify;                     /* notification type */
  void (*sigev_notify_function) (sigval_t); /* notification function */
  pthread_attr_t *sigev_notify_attributes; /* notification attributes */
} sigevent_t;

But I don't see an include for the pthread gear in the signal.h header file.

I found one past message that's similar
(https://cygwin.com/ml/cygwin/2016-06/msg00458.html), but its reported
as an upstream bug. I don't think it applies here since the pthread
data structure is used without an apparent declaration.

Can anyone confirm things are (not?) working as expected? If things
are working as expected, then hints to work around the failure would
be appreciated.

Thanks in advance,

Jeff

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