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Preprocessor problem on Cygwin


Every now and then, I try my (bad) luck on Cygwin.  This time, I fell
prey of an apparent bug in the version of the Cygwin dll I had
installed: it sets errno even when lstat() succeeds, which breaks
cpp's pathname simplification code.

Even though I believe this is actually a bug in Cygwin, I thought I'd
work around the problem, that might well be present in other OSs, with
this simple patch in GCC.  Ok for mainline?  Ok for branch?

Index: gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* cppfiles.c (remove_component_p): Don't assume lstat/stat will
	keep errno unchanged on success.

Index: gcc/cppfiles.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cppfiles.c,v
retrieving revision 1.117
diff -u -p -r1.117 cppfiles.c
--- gcc/cppfiles.c 2001/05/05 11:12:19 1.117
+++ gcc/cppfiles.c 2001/05/22 09:49:39
@@ -1027,6 +1027,12 @@ remove_component_p (path)
   result = stat (path, &s);
 #endif
 
+  /* There's no guarantee that errno will be unchanged, even on
+     success.  Cygwin's lstat(), for example, will often set errno to
+     ENOSYS.  In case of success, reset errno to zero.  */
+  if (result == 0 && errno != 0)
+    errno = 0;
+
   return result == 0 && S_ISDIR (s.st_mode);
 }
 

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me

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