It would be nice to have a configure option to disable/enable including the POSIX function tmpnam.
It may give Guile a more "code secure" option to have the default be disabled.

I tried to generate a patch, but I could not get it to work both ways (disable and enable).  My autoconf
knowledge and skills are lacking. 

Here is what I tried (THIS DOES NOT WORK)

--- libguile/posix.c-orig       2017-10-24 05:28:30.000000000 -0700
+++ libguile/posix.c    2017-10-24 05:28:51.000000000 -0700
@@ -1557,6 +1557,7 @@
 }
 #undef FUNC_NAME
 
+#ifdef ENABLE_TMPNAM
 #ifdef L_tmpnam
 
 SCM_DEFINE (scm_tmpnam, "tmpnam", 0, 0, 0,
@@ -1580,6 +1581,7 @@
 #undef FUNC_NAME
 
 #endif
+#endif
 
 SCM_DEFINE (scm_tmpfile, "tmpfile", 0, 0, 0,
             (void),

--- configure.ac-orig   2017-10-24 05:21:56.000000000 -0700
+++ configure.ac        2017-10-25 16:07:34.000000000 -0700
@@ -164,6 +164,10 @@
   [  --disable-regex         omit regular expression interfaces],,
   enable_regex=yes)
 
+AC_ARG_ENABLE(tmpnam,
+  [  --enable-tmpnam         enable POSIX tmpnam],
+  enable_tmpnam=yes, enable_tmpnam=no)
+
 AC_ARG_ENABLE([deprecated],
   AS_HELP_STRING([--disable-deprecated],[omit deprecated features]))

^--- DOES NOT WORK