Re: git on HP NonStop

2012-08-23 Thread Andreas Ericsson
On 08/22/2012 06:38 PM, Joachim Schmitz wrote:
 
 
 -Original Message-
 From: Junio C Hamano [mailto:gits...@pobox.com]
 Sent: Tuesday, August 21, 2012 4:06 AM
 To: Joachim Schmitz
 Cc: 'Johannes Sixt'; 'Jan Engelhardt'; git@vger.kernel.org
 Subject: Re: git on HP NonStop

 Joachim Schmitz j...@schmitz-digital.de writes:

 OK, so let's have a look at code, current git, builtin/cat-file.c,
 line 196:
  void *contents = contents;

 This variable is set later in an if branch (if (print_contents ==
 BATCH), but not in the else branch. It is later used always under the
 same condition as the one under which it is set.
 Apparently is is malloc_d storage (there a free(content);), so
 there's no harm al all in initializing it with NULL, even if it only
 appeases a stupid compiler.

 It actually is harmful.  See below.
 
 Harmful to initialize with NULL or to use that undefined behavoir?
 
 I checked what our compiler does here: after having warned about vlues us
 used before it is set: it actually dies seem to have initializes the value
 to 0 resp. NULL.
 So here there's no harm done in avoiding undefined behavior and set it to 0
 resp NULL in the first place.
 

There is harm in tricking future programmers into thinking that the
initialization actually means something, which some of them do.

It's unlikely that you're the one to maintain that code forever, and
the var = var idiom is used widely within git with a clear meaning
as a hint to programmers who read a bit of git code. If they aren't
used to that idiom, they usually investigate it in the code and
pretty quickly realize that what it means.


-- 
Andreas Ericsson   andreas.erics...@op5.se
OP5 AB www.op5.se
Tel: +46 8-230225  Fax: +46 8-230231

Considering the successes of the wars on alcohol, poverty, drugs and
terror, I think we should give some serious thought to declaring war
on peace.
--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


RE: git on HP NonStop

2012-08-23 Thread Joachim Schmitz
 From: Andreas Ericsson [mailto:a...@op5.se]
 Sent: Thursday, August 23, 2012 10:24 AM
 To: Joachim Schmitz
 Cc: 'Junio C Hamano'; 'Johannes Sixt'; 'Jan Engelhardt'; git@vger.kernel.org
 Subject: Re: git on HP NonStop
 
 On 08/22/2012 06:38 PM, Joachim Schmitz wrote:
 
 
  -Original Message-
  From: Junio C Hamano [mailto:gits...@pobox.com]
  Sent: Tuesday, August 21, 2012 4:06 AM
  To: Joachim Schmitz
  Cc: 'Johannes Sixt'; 'Jan Engelhardt'; git@vger.kernel.org
  Subject: Re: git on HP NonStop
 
  Joachim Schmitz j...@schmitz-digital.de writes:
 
  OK, so let's have a look at code, current git, builtin/cat-file.c,
  line 196:
   void *contents = contents;
 
  This variable is set later in an if branch (if (print_contents ==
  BATCH), but not in the else branch. It is later used always under the
  same condition as the one under which it is set.
  Apparently is is malloc_d storage (there a free(content);), so
  there's no harm al all in initializing it with NULL, even if it only
  appeases a stupid compiler.
 
  It actually is harmful.  See below.
 
  Harmful to initialize with NULL or to use that undefined behavoir?
 
  I checked what our compiler does here: after having warned about vlues us
  used before it is set: it actually dies seem to have initializes the value
  to 0 resp. NULL.
  So here there's no harm done in avoiding undefined behavior and set it to 0
  resp NULL in the first place.
 
 
 There is harm in tricking future programmers into thinking that the
 initialization actually means something, which some of them do.

Hmm, OK, I can agree to that.

 It's unlikely that you're the one to maintain that code forever, 

It is unlike for me to ever have to maintain this code.
Currently that's Junio's job and I won't apply for in ;-)

 and the var = var idiom is used widely within git 

This is overstating it a bit. I went thru the entire code and reported all 
places I could find in an earlier email.
I went back and counted: It is used in 11 files, at 15 places, for 21 
variables. 
OK, I may have missed  a few more that were in code paths my compiler didn't 
see, but still some 21+ isn't really much.

with a clear meaning

Only if you call undefined behavior a  'clear meaning!

 as a hint to programmers who read a bit of git code. If they aren't
 used to that idiom, they usually investigate it in the code and
 pretty quickly realize that what it means.

Whether I realize what it means, is irrelevant, my compiler does not and warns 
about it, and as per the ANSI/ICO C standard it
invokes undefined behavior.

If a proper initialization is meaningless for these cases, don't do them at 
all, let the stupid compiler complain about it and the
clever programmer check whether the warning is useful, but don't avoid a 
compiler warning on one compiler by introducing undefined
behavior and provoke a compiler warning on another.

Bye, Jojo

--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


RE: git on HP NonStop

2012-08-22 Thread Joachim Schmitz


 -Original Message-
 From: Junio C Hamano [mailto:gits...@pobox.com]
 Sent: Tuesday, August 21, 2012 4:06 AM
 To: Joachim Schmitz
 Cc: 'Johannes Sixt'; 'Jan Engelhardt'; git@vger.kernel.org
 Subject: Re: git on HP NonStop
 
 Joachim Schmitz j...@schmitz-digital.de writes:
 
  OK, so let's have a look at code, current git, builtin/cat-file.c,
  line 196:
  void *contents = contents;
 
  This variable is set later in an if branch (if (print_contents ==
  BATCH), but not in the else branch. It is later used always under the
  same condition as the one under which it is set.
  Apparently is is malloc_d storage (there a free(content);), so
  there's no harm al all in initializing it with NULL, even if it only
  appeases a stupid compiler.
 
 It actually is harmful.  See below.

Harmful to initialize with NULL or to use that undefined behavoir?

I checked what our compiler does here: after having warned about vlues us
used before it is set: it actually dies seem to have initializes the value
to 0 resp. NULL.
So here there's no harm done in avoiding undefined behavior and set it to 0
resp NULL in the first place.

  The next one, builtin/fast-export.c, line 486:
  struct commit *commit = commit; it is set in a switch
  statement, but not in every case, as far as I can see.
  Hmm, maybe it is, and I just get lost in the code And it is used
  directly after the switch, hopefully set to something reasonable.
  Why take the risk and not set it to NULL?
 
 Ditto.
 
  Next one, builtin/rev-list.c, line 390:
  int reaches = reaches, all = all;
 
  revs.commits = find_bisection(revs.commits, reaches,
all,
bisect_find_all);
 
  Seem pretty pointless to initialize them, provided find_bisection
  doesn't read them. Does it?
 
 That is why they are not initializations but marks to the compiler to
signal you
 may be stupid enough to think they are used before initialized or
assigned, but
 that is not the case.  Initializing them would be pointless.
 
  Next one, fast-import.c, line 2268:
  struct object_entry *oe = oe;
 
  os gets set in en if and an else branch, but not in then intermediate
  else if branch!
 
 Look again.  If the recent code is too complex for you to understand, go
back to
 10e8d68 (Correct compiler warnings in fast-import., 2007-02-06) and read
the
 function.
 
 The control flow of the early part of that function dictates that either
oe is
 assigned *or* inline_data is set to 1.  When inline_data is false, oe is
always
 set.
 
 The compiler was too stupid to read that, and that is why the
 (confusing) idiom to mark it for the stupid compiler was used.
 
 There are a few reasons why I do not think this self-assignment idiom or
 initializing the variable to an innocuous-looking random value is a
particularly
 good thing to do when you see compiler warnings.
 
 If the compiler suspects the variable might be unused, you should always
look
 at it and follow the flow yourself.  Once you know it is a false alarm,
you can
 use the idiom to squelch the warning, and it at the same serves as a note
to
 others that you verified the flow and made sure it is a false warning.
 
 When the next person wants to touch the code, if the person knows the use
of
 the idiom, it only serves as a warning to be extra careful not to
introduce a new
 codepath that reads the variable without setting, as the compiler no
longer
 helps him.  If the person who touches the code is as clueless as the
compiler
 and cannot follow the codepath to see the variable is never used
uninitialized,
 the result will be a lot worse.
 
 That is the reason why I do not think the idiom to squelch the compiler is
such a
 good thing.  Careless people touch the code, so oe = oe initialization
carefully
 placed in the original version does not necessarily stay as a useful
 documentation.
 
 But if you use oe = NULL as a way to squelch the warning in the first
place, it
 is no better than oe = oe.  In a sense, it is even worse, as it just
looks like any
 other initialization and gives a false impression that the remainder of
the code
 is written in such a way that it tolerates oe being NULL in any codepath,
or
 there is some assignment before that before the code reaches places where
oe
 cannot be NULL.  That is different from what oe = oe initializaion
documents--
 -in the codepath protected by if (inline_data), it isn't just oe can
safely be
 NULL there; instead it is oe can safely be *any* value there, because we
don't
 use it.  Of course, if you explicitly initialized oe to NULL, even if you
introduce
 a codepath where oe cannot be NULL later, you won't get a warning from the
 compiler, so it is no better than oe = oe.
 
 And that is the reason why I do not think initialization to an
innocuous-looking
 random value (e.g. NULL) is a good answer, either.
 
 When both are not good, replacing oe = oe with oe = NULL didn't make
 much sense

RE: git on HP NonStop

2012-08-20 Thread Joachim Schmitz
 From: Jan Engelhardt [mailto:jeng...@inai.de]
 Sent: Sunday, August 19, 2012 6:26 PM
 To: Joachim Schmitz
 Cc: 'Junio C Hamano'; git@vger.kernel.org
 Subject: RE: git on HP NonStop
 
 
 On Tuesday 2012-08-14 17:52, Joachim Schmitz wrote:
  @@ -98,6 +99,11 @@
  #include stdlib.h
  #include stdarg.h
  #include string.h
 +#ifdef __TANDEM
 +# include strings.h /* for strcasecmp() */
 +  typedef int intptr_t; /* not int * ?!? */
 +  typedef unsigned int uintptr_t; /* not unsigned int * ?!? */
 
 Of course not. intptr_t is an integral value capable of holding a pointer;
it is not
 a pointer to int (because that would really be redundant to int*.)

OK, thanks for the clarification.

Another issue I stumbled across:
There are numerous places (well, some 10) were something like the following
is done

int var = var;
char *othervar = othervar;

Here this leads to Compiler warnings  'variable var is used before its
value is set' on NonStop. This self-initialization seems to be a GCC
extension (?), but even gcc has a -Winit-self option to warn about this.
Shouldn't that better be like the following?

int var = 0;
char *othervar = NULL;

What is the reason for using that self-init stuff? I don't think it is
really portable, is it?

Bye, Jojo

--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


Re: git on HP NonStop

2012-08-20 Thread Johannes Sixt
Am 8/20/2012 12:36, schrieb Joachim Schmitz:
 int var = var;
 char *othervar = othervar;
 
 ... 

 What is the reason for using that self-init stuff? I don't think it is
 really portable, is it?

It is used to avoid var may be used uninitialized warnings for some
compilers. Officially (according to the C standard), it is undefined
behavior. But I've observed considerable resistance by Junio to fix this
properly. Therefore, unless you can show that your compiler generates
unusable code you better live with the self-initialization warnings.

-- Hannes
--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


RE: git on HP NonStop

2012-08-20 Thread Joachim Schmitz
 From: Johannes Sixt [mailto:j.s...@viscovery.net]
 Sent: Monday, August 20, 2012 12:57 PM
 To: Joachim Schmitz
 Cc: 'Jan Engelhardt'; 'Junio C Hamano'; git@vger.kernel.org
 Subject: Re: git on HP NonStop
 
 Am 8/20/2012 12:36, schrieb Joachim Schmitz:
  int var = var;
  char *othervar = othervar;
 
  ...
 
  What is the reason for using that self-init stuff? I don't think it is
  really portable, is it?
 
 It is used to avoid var may be used uninitialized warnings for some
compilers.

Well, it results in a similar warning on NonStop. var is used before it is
set and I think this is equally bad.
In either case we don't know what the content of that var is.

E.g. in wt_status.c the variable 'status' is set at only one place, but
later it is switched on. If lucky we get to the default case and die.
So why not just 
int status = 0;

 Officially (according to the C standard), it is undefined behavior. 

Yes, I had that suspicion. Not good to rely in this...

 But I've observed considerable resistance by Junio to fix this properly. 

What's the  reason behind that?

 Therefore, unless
 you can show that your compiler generates unusable code you better live
with
 the self-initialization warnings.

So far I can't, so I guess I'll have to live with the warnings, but don't
quite like it.
 
 -- Hannes

Bye, Jojo

--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


Re: git on HP NonStop

2012-08-20 Thread Junio C Hamano
Johannes Sixt j.s...@viscovery.net writes:

 Am 8/20/2012 12:36, schrieb Joachim Schmitz:
 int var = var;
 char *othervar = othervar;
 
 ... 

 What is the reason for using that self-init stuff? I don't think it is
 really portable, is it?

 It is used to avoid var may be used uninitialized warnings for some
 compilers. Officially (according to the C standard), it is undefined
 behavior. But I've observed considerable resistance by Junio to fix this
 properly.

I had resisted

-   int foo = foo;
+   int foo = 0;

in the past.  If some compiler is not seeing that foo is never
used uninitialized, such a compiler will generate an unnecessary
initialization, so it is not a _proper_ fix anyway (in fact, I do
not think a proper fix exists, short of simplifying the code so that
less sophisticated compilers can see that foo is never used
uninitialized).

So, no, I never resisted a proper fix.  I resisted swapping an
unsatisfactory workaround with another.

Between the two unsatisfactory workarounds, the latter (explicit
and unnecessary assignment to an innocuous value) is lessor of two
evils, so I do not particularly mind it, though.  Indeed, I think
more recent history shows that we have such changes.


--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


RE: git on HP NonStop

2012-08-20 Thread Joachim Schmitz
 From: Junio C Hamano [mailto:gits...@pobox.com]
 Sent: Monday, August 20, 2012 6:30 PM
 To: Johannes Sixt
 Cc: Joachim Schmitz; 'Jan Engelhardt'; git@vger.kernel.org
 Subject: Re: git on HP NonStop
 
 Johannes Sixt j.s...@viscovery.net writes:
 
  Am 8/20/2012 12:36, schrieb Joachim Schmitz:
  int var = var;
  char *othervar = othervar;
 
  ...
 
  What is the reason for using that self-init stuff? I don't think it
  is really portable, is it?
 
  It is used to avoid var may be used uninitialized warnings for some
  compilers. Officially (according to the C standard), it is undefined
  behavior. But I've observed considerable resistance by Junio to fix
  this properly.
 
 I had resisted
 
   -   int foo = foo;
 + int foo = 0;
 
 in the past.  If some compiler is not seeing that foo is never used
uninitialized,
 such a compiler will generate an unnecessary initialization, so it is not
a
 _proper_ fix anyway (in fact, I do not think a proper fix exists, short of
 simplifying the code so that less sophisticated compilers can see that
foo is
 never used uninitialized).
 
 So, no, I never resisted a proper fix.  I resisted swapping an
unsatisfactory
 workaround with another.
 
 Between the two unsatisfactory workarounds, the latter (explicit and
 unnecessary assignment to an innocuous value) is lessor of two evils, so I
do not
 particularly mind it, though.  Indeed, I think more recent history shows
that we
 have such changes.

OK, so let's have a look at code, current git,
builtin/cat-file.c, line 196:
void *contents = contents;

This variable is set later in an if branch (if (print_contents == BATCH),
but not in the else branch. It is later used always under the same condition
as the one under which it is set.
Apparently is is malloc_d storage (there a free(content);), so there's no
harm al all in initializing it with NULL, even if it only appeases a stupid
compiler.

The next one, builtin/fast-export.c, line 486:
struct commit *commit = commit;
it is set in a switch statement, but not in every case, as far as I can see.
Hmm, maybe it is, and I just get lost in the code
And it is used directly after the switch, hopefully set to something
reasonable.
Why take the risk and not set it to NULL?

Next one, builtin/rev-list.c, line 390:
int reaches = reaches, all = all;

revs.commits = find_bisection(revs.commits, reaches, all,
  bisect_find_all);

Seem pretty pointless to initialize them, provided find_bisection doesn't
read them. Does it?
I'm too Next one, lazy to check... I'd just set them to 0 and stop worrying.

Next one, fast-import.c, line 2268:
struct object_entry *oe = oe;

os gets set in en if and an else branch, but not in then intermediate else
if branch!
It is checked for !NULL later, so it should really get initialized to NULL
in the first place!

Same file, line 2437, same variable name, same story!
Same file, line 2616, variable e, it is used in an if branch but set after
that! 
Same file again, line 2917, variable oe again. Same story as above.

Next file, ll-merge.c, line
static const struct ll_merge_options default_opts;
Somewhat different story here, compiler warning claims  const variable
default_opts requires an initializer
Possible fix:
static const struct ll_merge_options default_opts = {0};

next file, match-trees.c, line 75ff:
const unsigned char *elem1 = elem1;
const unsigned char *elem2 = elem2;
const char *path1 = path1;
const char *path2 = path2;
unsigned mode1 = mode1;
unsigned mode2 = mode2;
Some get set, some not, depending on code path, but all get used, with
possibly bogus content.

Next file, merge-recursive.c, line 1903:
struct tree *mrtree = mrtree;
passed on my address to another function, which hopefully knows how to treat
it. It woult be learer and simpler to just have
struct tree *mrtree = NULL;
wouldn't it?

Next file, run-command.c, line 272:
int failed_errno = failed_errno;
Set deeply nested in some cases. Seems to be used reasonably, but again, why
take chanses= 0 is a goot errno ;-)

Next file, submodule.c, line 265:
struct commit *left = left, *right = right;
As far as I can see it is not set properly before it gets used in some
cases.

Next filen, transport.c, line 106:
int cmp = cmp, len;
I seem to see code paths whet it is used without being set properly

Next file, vcs-svn/svndiff.c, line 299 oh, that one has been fixed and
initialized to -1.

Next (and last) file, wt-status.c, line 267:
int status = status;
It apparently does get set properly before use. So here it once may once
again just make a compiler happy to set it to 0.

Bye, Jojo

--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More

Re: git on HP NonStop

2012-08-20 Thread Junio C Hamano
Joachim Schmitz j...@schmitz-digital.de writes:

 OK, so let's have a look at code, current git,
 builtin/cat-file.c, line 196:
 void *contents = contents;

 This variable is set later in an if branch (if (print_contents == BATCH),
 but not in the else branch. It is later used always under the same condition
 as the one under which it is set.
 Apparently is is malloc_d storage (there a free(content);), so there's no
 harm al all in initializing it with NULL, even if it only appeases a stupid
 compiler.

It actually is harmful.  See below.

 The next one, builtin/fast-export.c, line 486:
 struct commit *commit = commit;
 it is set in a switch statement, but not in every case, as far as I can see.
 Hmm, maybe it is, and I just get lost in the code
 And it is used directly after the switch, hopefully set to something
 reasonable.
 Why take the risk and not set it to NULL?

Ditto.

 Next one, builtin/rev-list.c, line 390:
 int reaches = reaches, all = all;

 revs.commits = find_bisection(revs.commits, reaches, all,
   bisect_find_all);

 Seem pretty pointless to initialize them, provided find_bisection doesn't
 read them. Does it?

That is why they are not initializations but marks to the compiler
to signal you may be stupid enough to think they are used before
initialized or assigned, but that is not the case.  Initializing
them would be pointless.

 Next one, fast-import.c, line 2268:
 struct object_entry *oe = oe;

 os gets set in en if and an else branch, but not in then intermediate else
 if branch!

Look again.  If the recent code is too complex for you to
understand, go back to 10e8d68 (Correct compiler warnings in
fast-import., 2007-02-06) and read the function.

The control flow of the early part of that function dictates that
either oe is assigned *or* inline_data is set to 1.  When inline_data
is false, oe is always set.

The compiler was too stupid to read that, and that is why the
(confusing) idiom to mark it for the stupid compiler was used.

There are a few reasons why I do not think this self-assignment
idiom or initializing the variable to an innocuous-looking random
value is a particularly good thing to do when you see compiler
warnings.

If the compiler suspects the variable might be unused, you should
always look at it and follow the flow yourself.  Once you know it is
a false alarm, you can use the idiom to squelch the warning, and it
at the same serves as a note to others that you verified the flow
and made sure it is a false warning.

When the next person wants to touch the code, if the person knows
the use of the idiom, it only serves as a warning to be extra
careful not to introduce a new codepath that reads the variable
without setting, as the compiler no longer helps him.  If the person
who touches the code is as clueless as the compiler and cannot
follow the codepath to see the variable is never used uninitialized,
the result will be a lot worse.

That is the reason why I do not think the idiom to squelch the
compiler is such a good thing.  Careless people touch the code, so
oe = oe initialization carefully placed in the original version
does not necessarily stay as a useful documentation.

But if you use oe = NULL as a way to squelch the warning in the
first place, it is no better than oe = oe.  In a sense, it is even
worse, as it just looks like any other initialization and gives a
false impression that the remainder of the code is written in such a
way that it tolerates oe being NULL in any codepath, or there is
some assignment before that before the code reaches places where oe
cannot be NULL.  That is different from what oe = oe initializaion
documents---in the codepath protected by if (inline_data), it
isn't just oe can safely be NULL there; instead it is oe can
safely be *any* value there, because we don't use it.  Of course,
if you explicitly initialized oe to NULL, even if you introduce a
codepath where oe cannot be NULL later, you won't get a warning from
the compiler, so it is no better than oe = oe.

And that is the reason why I do not think initialization to an
innocuous-looking random value (e.g. NULL) is a good answer, either.

When both are not good, replacing oe = oe with oe = NULL didn't
make much sense, especially when the former _could_ be used better
by more careful people.  And that is the resistance J6t remembers.

But when recent compilers started to warn oe = oe that itself is
undefined, the equation changed.  The idiom ceased to be a way to
squelch the incorrect compiler warning (which was the primary point
of its use---the documentation value is secondary, as what we
document is we are squelching a false alarm, but we no longer are
squelching anything).

See 4a5de8d (vcs-svn: avoid self-assignment in dummy initialization
of pre_off, 2012-06-01), and 58ebd98 (vcs-svn/svndiff.c: squelch
false unused warning from gcc, 2012-01-27) that it updated, for 

RE: git on HP NonStop

2012-08-19 Thread Jan Engelhardt

On Tuesday 2012-08-14 17:52, Joachim Schmitz wrote:
 @@ -98,6 +99,11 @@
 #include stdlib.h
 #include stdarg.h
 #include string.h
+#ifdef __TANDEM
+# include strings.h /* for strcasecmp() */
+  typedef int intptr_t; /* not int * ?!? */
+  typedef unsigned int uintptr_t; /* not unsigned int * ?!? */

Of course not. intptr_t is an integral value capable of holding
a pointer; it is not a pointer to int (because that would really
be redundant to int*.)
--
To unsubscribe from this list: send the line unsubscribe git in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


RE: git on HP NonStop

2012-08-14 Thread Joachim Schmitz
 From: Junio C Hamano [mailto:gits...@pobox.com]
 Sent: Tuesday, August 14, 2012 4:44 PM
 To: Joachim Schmitz
 Subject: Re: git on HP NonStop
 
 Joachim Schmitz j...@schmitz-digital.de writes:
 
  Interesting, I never mentioned Tandem did I, But still you recognized
  HP NonStop as that.
 
 No, *you* did in your patch #ifdef.

Ah, I see.

  Well, I do care about that platform,  but if you don't, there's not
  much point in me trying to get Tandem specific patches applied, is it?
 
 As long as the change is isolated (i.e. compilation without #define
TANDEM

__TANDEM actually

 for other people will produce byte-for-byte identical result as before),
and
 cleanly made (i.e. the resulting source code is not littered with #ifdef
 TANDEM in many places), I do not think there is a reason not to have such
a
 patchset.

It isn't in many places, only 2 places in git-compat-util.h so far:
/usr/local/bin/diff -EBbu ./git-compat-util.h.orig ./git-compat-util.h
--- ./git-compat-util.h.orig2012-07-30 15:50:38 -0500
+++ ./git-compat-util.h 2012-08-12 11:26:46 -0500
@@ -74,7 +74,8 @@
 # define _XOPEN_SOURCE 500
 # endif
 #elif !defined(__APPLE__)  !defined(__FreeBSD__)  !defined(__USLC__) 
\
-  !defined(_M_UNIX)  !defined(__sgi)  !defined(__DragonFly__)
+  !defined(_M_UNIX)  !defined(__sgi)  !defined(__DragonFly__)  \
+  !defined(__TANDEM)
 #define _XOPEN_SOURCE 600 /* glibc2 and AIX 5.3L need 500, OpenBSD needs
600 for S_ISLNK() */
 #define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
 #endif
 @@ -98,6 +99,11 @@
 #include stdlib.h
 #include stdarg.h
 #include string.h
+#ifdef __TANDEM
+# include strings.h /* for strcasecmp() */
+  typedef int intptr_t; /* not int * ?!? */
+  typedef unsigned int uintptr_t; /* not unsigned int * ?!? */
+#endif
 #include errno.h
 #include limits.h
 #include sys/param.h

Too much? The 2nd part is not necessary NonStop specific, any idea for a
better way?

There there's Makefile:
/usr/local/bin/diff -EBbu ./Makefile.orig ./Makefile
--- ./Makefile.orig 2012-07-30 15:50:38 -0500
+++ ./Makefile  2012-08-14 06:07:16 -0500
@@ -1297,6 +1297,45 @@
NO_CURL =
NO_EXPAT =
 endif
+ifeq ($(uname_S),NONSTOP_KERNEL)
+   CC = cc -c99 # needs some C99 features, inline is just one of them
+   CFLAGS= -g -O
+   prefix = /usr/local
+
+   # as detected by './configure'
+   #NO_CURL = YesPlease # missdetected, disabled, see below
+   NEEDS_SSL_WITH_CURL = YesPlease # added manually, see above
+   HAVE_LIBCHARSET_H=YesPlease
+   NEEDS_LIBICONV = YesPlease # needs libiconv first, changed further
down
+   NO_SYS_SELECT_H=UnfortunatelyYes
+   NO_D_TYPE_IN_DIRENT = YesPlease
+   NO_HSTRERROR=YesPlease
+   NO_STRCASESTR=YesPlease
+   NO_FNMATCH_CASEFOLD = YesPlease
+   NO_MEMMEM = YesPlease
+   NO_STRLCPY = YesPlease
+   NO_SETENV = YesPlease
+   NO_UNSETENV = YesPlease
+   NO_MKDTEMP = YesPlease
+   NO_MKSTEMPS = YesPlease
+   OLD_ICONV=UnfortunatelyYes # currently libiconv-1.9.1
+   NO_REGEX=YesPlease # Why? ToDo?
+   NO_PTHREADS=UnfortunatelyYes # ToDo? Using PUT, maybe?
+
+   # our's are in ${prefix}/bin
+   PERL_PATH = ${prefix}/bin/perl
+   PYTHON_PATH = ${prefix}/bin/python
+
+   # not detected (nor checked for) by './configure'
+   COMPAT_CFLAGS += -DSA_RESTART=0 # we don't have SA_RESTART on
NonStop
+   COMPAT_CFLAGS += -DHAVE_STRING_H=1 # needed in
compat/fnmatch/fnmatch.c
+   NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease # we don't have that on
NonStop
+   NO_NSEC = YesPlease # we don't have that on NonStop
+   NO_PREAD = YesPlease # we could use floss_pread though?
+   NO_MMAP = YesPlease # we could use floss_mmap though?
+   # newly implemented further down
+   NO_POLL = YesPlease # we could use floss_poll though?
+endif
 ifneq (,$(findstring MINGW,$(uname_S)))
pathsep = ;
NO_PREAD = YesPlease
@@ -1526,6 +1565,11 @@
LIB_4_CRYPTO = $(OPENSSL_LINK) -lcrypto
 endif
 endif
+ifndef NO_GETTEXT
+ifndef LIBC_CONTAINS_LIBINTL
+   EXTLIBS += -lintl
+endif
+endif
 ifdef NEEDS_LIBICONV
ifdef ICONVDIR
BASIC_CFLAGS += -I$(ICONVDIR)/include
@@ -1538,11 +1582,6 @@
 ifdef NEEDS_LIBGEN
EXTLIBS += -lgen
 Endif
-ifndef NO_GETTEXT
-ifndef LIBC_CONTAINS_LIBINTL
-   EXTLIBS += -lintl
-endif
-endif
 ifdef NEEDS_SOCKET
EXTLIBS += -lsocket
 endif
@@ -1591,6 +1630,11 @@
BASIC_CFLAGS += -DNO_GETTEXT
USE_GETTEXT_SCHEME ?= fallthrough
 endif
+ifdef NO_POLL
+   NO_SYS_POLL_H = YesPlease
+   COMPAT_CFLAGS += -DNO_POLL -Icompat/win32 # so it finds poll.h
+   COMPAT_OBJS += compat/win32/poll.o
+endif
 ifdef NO_STRCASESTR
COMPAT_CFLAGS += -DNO_STRCASESTR
COMPAT_OBJS += compat/strcasestr.o

How das that look to you?

  Finally, I would prefer to see any message that is addressed to me as
  the project maintainer to be Cc'ed to the list.  I feel 80% of my