Clean up errno reporting and fix some errno-reporting bugs.

* callproc.c (Fcall_process):
* fileio.c (Fcopy_file, Finsert_file_contents, Fwrite_region):
* process.c (create_process, Fmake_network_process):
* unexaix.c (report_error):
* unexcoff.c (report_error):
Be more careful about reporting the errno of failed operations.
The code previously reported the wrong errno sometimes.
Also, prefer report_file_errno to setting errno + report_file_error.
(Fcall_process): Look at openp return value rather than at path,
as that's a bit faster and clearer when there's a numeric predicate.
* fileio.c (report_file_errno): New function, with most of the
old contents of report_file_error.
(report_file_error): Use it.
(Ffile_exists_p, Ffile_accessible_directory_p):
Set errno to 0 when it is junk.
* fileio.c (Faccess_file):
* image.c (x_create_bitmap_from_file):
Use faccessat rather than opening the file, to avoid the hassle of
having a file descriptor open.
* lisp.h (report_file_errno): New decl.
* lread.c (Flocate_file_internal): File descriptor 0 is valid, too.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/unexcoff.c b/src/unexcoff.c
index 6b2a3336c8a..c467e59a665 100644
--- a/src/unexcoff.c
+++ b/src/unexcoff.c
@@ -127,9 +127,10 @@ static int pagemask;
 static void
 report_error (const char *file, int fd)
 {
+  int err = errno;
   if (fd)
     emacs_close (fd);
-  report_file_error ("Cannot unexec", Fcons (build_string (file), Qnil));
+  report_file_errno ("Cannot unexec", Fcons (build_string (file), Qnil), err);
 }
 
 #define ERROR0(msg) report_error_1 (new, msg, 0, 0); return -1