Re: git 1.6.6.1 on glibc 2.2

[Jonathan Nieder <jrnieder@gmail.com>]

Gabor Z. Papp wrote:
>| Gabor Z. Papp wrote:
 
>|> trying to compile git 1.6.6.1 on Linux 2.4.37.7, glibc 2.2.5:
>|> 
>|> read-cache.c: In function 'fill_stat_cache_info':
>|> read-cache.c:72: error: 'struct stat' has no member named 'st_ctim'
[...] 
> Thanks Jonathan, compiles fine defining NO_NSEC, but my glibc is 2.2.5
> and the comment abot USE_NSEC says it requires at least glibc
> 2.2.4. Maybe the comment is wrong? glibc 2.3.6 compiles fine.

Hmm, in the glibc changelog I find this, from ChangeLog.14:

| 2003-01-04  Andreas Schwab  <schwab@suse.de>
|
|	* sysdeps/unix/sysv/linux/m68k/bits/stat.h: Add nanosecond fields.

That’s around the time of glibc 2.3.2.

The stat(2) man page tells a little more:

| Since kernel 2.5.48, the stat structure supports nanosecond resolution for
| the  three  file timestamp fields.  Glibc exposes the nanosecond component
| of each field using names either  of  the  form  st_atim.tv_nsec,  if  the
| _BSD_SOURCE  or _SVID_SOURCE feature test macro is defined, or of the form
| st_atimensec, if neither of these macros is defined.  On file systems that
| do not support sub-second timestamps, these nanosecond fields are returned
| with the value 0.

Searching a little harder yields commit cvs/glibc-2_3_2~418
(2002-12-31) of git://sourceware.org/git/glibc.git, in which the
feature was added.  There’s a lovely discussion about it from then on
libc-alpha. [1]

The comment you mention is from commit bdd4da5 (Make nsec checking
optional, 2005-04-13); I am guessing 2.2.4 was just mentioned as a lower
bound.

So how about something like the following?  Please feel free to
write something better --- in particular, I am not sure the
documentation for USE_NSEC is the most obvious place to look when
something goes wrong.

Thanks,
Jonathan

[1] http://sourceware.org/ml/libc-alpha/2002-12/threads.html#00011

-- %< --
Subject: Makefile: document minimal glibc version supporting tv_nsec

Compiling git with the default settings and old glibc produces
errors like the following:

| read-cache.c: In function 'fill_stat_cache_info':
| read-cache.c:72: error: 'struct stat' has no member named 'st_ctim'

The Makefile seems to imply that versions after 2.2.4 should be
okay, but that is not true: NO_NSEC must be set to build with
glibc versions before 2.3.2.

Reported-by: Gabor Z. Papp <gzp@papp.hu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
diff --git a/Makefile b/Makefile
index fd7f51e..8ebc966 100644
--- a/Makefile
+++ b/Makefile
@@ -134,7 +134,7 @@ all::
 # "-Wl,-rpath=/path/lib" is used instead.
 #
 # Define USE_NSEC below if you want git to care about sub-second file mtimes
-# and ctimes. Note that you need recent glibc (at least 2.2.4) for this, and
+# and ctimes. Note that you need recent glibc (at least 2.3.2) for this, and
 # it will BREAK YOUR LOCAL DIFFS! show-diff and anything using it will likely
 # randomly break unless your underlying filesystem supports those sub-second
 # times (my ext3 doesn't).