🚀 go-pugleaf

RTFM!

Quoting from `man 2 intro' of my AT&T 3B1 UNIX manual set (and this manual
set dates from a decade ago -- UNIX has not changed in this respect during
this time):

Most of these calls have one or more error returns. **An error condition is
indicated by an otherwise impossible returned value.** [Emphasis mine] This
is almost always -1; the individual descriptions specify the details.  An
error number is also made available in the external variable *errno*. [Italics
theirs] *Errno* [italics theirs] **is not cleared** [emphasis mine] on success-
ful calls, so it should be test only after an error has been indicated.

You made a mistake.

tempnam() in the course of its internal processing may create one or more
error conditions that it recovers from itself.  E.g., it may create a
file name that is already in use.  Detecting this condition, it repeatly
generates more until it finds a name that is not in use.  `tempnam()' does
not clear errno afterwards!

Check for an error return from your system call or library call *first*!
*Only* if an error is indicated, should you check errno to determine what
error.

Randolph J. Herber, herber@fnalf.fnal.gov, +1 708 840 2966
(Speaking for myself and not for US, US DOE, FNAL nor URA.)
(Product, trade, or service marks herein belong to their respective owners.)

+From: "T.C. Zhao" <svec5@menudo.uh.edu>
+Newsgroups: comp.sys.sgi,comp.sys.sgi.bugs,comp.unix.ultrix
+Subject: tempnam(3S) bug, possibly on all MIPS
+Date: 19 Dec 92 04:23:37 GMT

+It appears that tempnam(3S) is broken on three MIPS machines I have
+access to:   IRIX 3.3, Ultrix 4.1, UMIPS 4.52:

+/* 
+ * check to see if tempnam has the errno bug.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>

+int main(int argc, char **argv)
+{
+   char *p;
+   errno = 0;
+   p = tempnam(0, 0);
+   if(errno) fprintf(stderr," tempnam is broken\n");
+   return 0;
+}