Re: [PATCH 1/3] timespec.3type: tv_nsec is impl-def-type, glibc llong not a bug

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Hey наб!

On 1/28/23 15:17, наб wrote:
n3091 accepts n3066, making it part of the next working draft and C23:
   https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3091.doc

Update timespec.3type appropriately, largely mirroring my paper.
Nice! :-)


Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
This is in many ways a followup to the patchset that originally added
the BUGS sexion to timespec.3type, root msgid of
   <ec1dcc655184f6cdaae40ff8b7970b750434e4ef.1638123425.git.nabijaczleweli@xxxxxxxxxxxxxxxxxx>

For ease of reference, n3066:
   https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3066.pdf
and the relevant part of n3091 (screenshot, it's a .doc):
   https://cohost.org/nabijaczleweli/post/922578-pog-pog

What happened in the end with nsec_t? Was it rejected, or are they still considering it?


2/3 and 3/3 only span the pages that matched git grep -l tv_nsec,
but that should be most of the relevant ones

  man3type/timespec.3type | 46 +++++++++++++----------------------------
  1 file changed, 14 insertions(+), 32 deletions(-)

diff --git a/man3type/timespec.3type b/man3type/timespec.3type
index 7cd80ce86..ca5533814 100644
--- a/man3type/timespec.3type
+++ b/man3type/timespec.3type
@@ -16,14 +16,27 @@ Standard C library
  .PP
  .B struct timespec {
  .BR "    time_t  tv_sec;" "   /* Seconds */"
-.BR "    long    tv_nsec;" "  /* Nanoseconds [" 0 ", " 999999999 "] */"
+.BR "    /*\(da*/   tv_nsec;" "  /* Nanoseconds [" 0 ", " 999999999 "] */"

I'm tempted to merge this patch.  It's sooo qute /*↓*/

Please use the digit separator \(aq for the big number.

  .B };
  .EE
  .SH DESCRIPTION
  Describes times in seconds and nanoseconds.
+.PP
+.I tv_nsec
+is of an implementation-defined signed type capable of holding the specified range.
+Under glibc, this is usually
+.IR long ,
+and
+.I long long
+on X32.
+It can safely be down-cast to any concrete 32-bit integer type for processing.

Ok.

  .SH STANDARDS
  C11 and later;
  POSIX.1-2001 and later.
+Prior to C23

A comma here?

+.I tv_nsec
+was
+.IR long .

Please move this to a new VERSIONS sexion.

  .SH NOTES
  The following headers also provide this type:
  .IR <aio.h> ,
@@ -33,37 +46,6 @@ The following headers also provide this type:
  .IR <sys/select.h> ,
  and
  .IR <sys/stat.h> .
-.SH BUGS
-Under glibc,
-.I tv_nsec
-is the
-.I syscall
-long,
-though this affects only fringe architectures like X32,
-which is ILP32, but uses the LP64 AMD64 syscall ABI.
-In reality, the field ends up being defined as:
-.PP
-.in +4n
-.EX
-#if __x86_64__ && __ILP32__  /* == x32 */
-    long long  tv_nsec;
-#else
-    long       tv_nsec;
-#endif
-.EE
-.in
-.PP
-This is a long-standing and long-enshrined glibc bug
-.UR https://sourceware.org/bugzilla/show_bug.cgi?id=16437
-.I #16437
-.UE ,
-and an incompatible extension to the standards;
-however, as even a 32-bit
-.I long
-can hold the entire
-.I tv_nsec
-range,
-it's always safe to forcibly down-cast it to the standard type.

Ok.

Cheers,

Alex

  .SH SEE ALSO
  .BR clock_gettime (2),
  .BR clock_nanosleep (2),

--
<http://www.alejandro-colomar.es/>

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