Re: gettimeofday module on cygwin

[Bruno Haible]

Eric Blake wrote:
> cygwin's <sys/time.h> declares struct
> timeval, then includes <sys/select.h>, which in turn includes <sys/time.h>
> to guarantee struct timeval is declared no matter which header was
> included first.  But once gnulib has decided that cygwin needs the
> replacement, it turns into the following:
> 
> include ./sys/time.h
>  first time, so...
>  include_next /usr/include/sys/time.h
>   declare struct timeval
>   include /usr/include/sys/select.h
>    include ./sys/time.h
>    second time, so...
>    define gettimeofday rpl_gettimeofday
>    declare gettimeofday (struct timeval*, void*);
>   declare gettimeofday (struct timeval*, struct timezone*)

I don't understand this sequence. Did you mean to indent it like this?

include ./sys/time.h
 first time, so...
 include_next /usr/include/sys/time.h
  declare struct timeval
  include /usr/include/sys/select.h
   include ./sys/time.h
    second time, so...
    define gettimeofday rpl_gettimeofday
    declare gettimeofday (struct timeval*, void*);
  declare gettimeofday (struct timeval*, struct timezone*)

Paul patched lib/time_.h so that it allows recursive includes on 2007-06-23;
appended is a proposed patch to do the same with lib/sys_time_.h.

> At any rate, is it necessary that gettimeofday.m4 insist that gettimeofday
> have void* as the type of the second parameter?

The gettimeofday redeclaration is fine. There is no need to blame it.

> Without -Werror,
> gnulib does not create ./sys/time.h, so this problem does not surface.

Maybe gnulib will create a sys/time.h for other reasons in the future.
Therefore it's not worthless to fix the problem now, even through -Werror
is unsupported by gnulib.

Bruno


2007-07-05  Bruno Haible  <address@hidden>

        * lib/sys_time_.h: Use a recursion-safe inclusion guard rather than
        a split double-inclusion guard. Needed for cygwin, where <sys/time.h>
        includes <cygwin/sys_time.h> which includes <sys/select.h> which
        include <sys/time.h>.
        Reported by Eric Blake.

--- lib/sys_time_.h     21 Jun 2007 04:39:11 -0000      1.7
+++ lib/sys_time_.h     5 Jul 2007 23:17:50 -0000
@@ -18,31 +18,35 @@
 
 /* Written by Paul Eggert.  */
 
-#ifndef _GL_SYS_TIME_H
+#if defined _GL_SYS_TIME_H
+
+/* Simply delegate to the system's header, without adding anything.  */
+# if @HAVE_SYS_TIME_H@
+#  @INCLUDE_NEXT@ @NEXT_SYS_TIME_H@
+# endif
 
-/* The include_next requires a split double-inclusion guard.  */
-#if @HAVE_SYS_TIME_H@
-# @INCLUDE_NEXT@ @NEXT_SYS_TIME_H@
 #else
-# include <time.h>
-#endif
 
-#ifndef _GL_SYS_TIME_H
-#define _GL_SYS_TIME_H
+# define _GL_SYS_TIME_H
+
+# if @HAVE_SYS_TIME_H@
+#  @INCLUDE_NEXT@ @NEXT_SYS_TIME_H@
+# else
+#  include <time.h>
+# endif
 
-#if ! @HAVE_STRUCT_TIMEVAL@
+# if ! @HAVE_STRUCT_TIMEVAL@
 struct timeval
 {
   time_t tv_sec;
   long int tv_usec;
 };
-#endif
+# endif
 
-#if @REPLACE_GETTIMEOFDAY@
-# undef gettimeofday
-# define gettimeofday rpl_gettimeofday
+# if @REPLACE_GETTIMEOFDAY@
+#  undef gettimeofday
+#  define gettimeofday rpl_gettimeofday
 int gettimeofday (struct timeval *restrict, void *restrict);
-#endif
+# endif
 
 #endif /* _GL_SYS_TIME_H */
-#endif /* _GL_SYS_TIME_H */