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Message-ID: <51811D36.2060104@gmx.de>
Date: Wed, 01 May 2013 15:48:38 +0200
From: Juan Manuel Guerrero <juan DOT guerrero AT gmx DOT de>
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To: djgpp-workers AT delorie DOT com
Subject: Re: The encoding of S_IFREG
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Reply-To: djgpp-workers AT delorie DOT com

Am 01.05.2013 14:24, schrieb Rugxulo:
 > On Wed, May 1, 2013 at 5:04 AM, Juan Manuel Guerrero
 > <juan DOT guerrero AT gmx DOT de> wrote:
 > >
 > > While I was trying to port patch 2.7.1, besides a lot of issues, I
 > > encountered
 > > the following problem:  DJGPP file mode encodes S_IFREG with 0x0000.
 > > Unfortunately the patch code checks if the file mode is valid at all by
 > > checking against zero.
 > >
 > > We could replace 0x0000 by 0x6000.  I am aware that this may introduce
 > > backward
 > > incompatibilities, but the benefits when a porting job is done are 
evident.
 >
 > At risk of stating the obvious, just #undef it locally and (re)
 > #define it with non-zero value.

This is what I do.  In the config.h file created by config.bat, a DJGPP
specific section is added that redefines S_IFREG and S_ISREG so that
they work with a value different from zero.


 > While it's possible that something would break if you changed this
 > globally, I'd be mighty surprised. AFAIK, the whole point of such
 > named constants is to avoid relying on hidden values.

This approach does not work with git style patches.  They may look
like this:

diff --git a/symlink b/symlink
new file mode 120000
index 0000000..12a8d8a
--- /dev/null
+++ b/symlink
@@ -0,0 +1 @@
+target1
\ No newline at end of file

As can be seen the file mode is coded in the patch. The octal 120000
encodes S_IFLNK on linux but if this number is assigned to djgpp's
st_mode it makes no sense.  It certainly does not match djgpp's value
of S_IFLNK and the port may work erratic when evaluated with S_ISLNK .
Of course, I have written a macro that maps the linux S_IFMT bits
to the corresponding djgpp ones leaving the rest unchanged.


Regards,
Juan M. Guerrero