Lose hope of running against guile 2.2 or earlier.

We have previously allowed versions 2.0 and 2.2 to get past the configure
stage, but all versions of guile before 3.0 have in fact failed to compile the
code due to syntax errors for some time now.

* build-aux/guix.scm:  package depends on guile@3
* configure.ac:  only look for guile version 3
* src/mcron/base.scm:  drop allowance for old-fashioned (version 2.0) select

build-aux/guix.scm

@@ -45,7 +45,7 @@
   (source (local-file (dirname %srcdir) #:recursive? #t
                       #:select? keep-mcron-file?))
   (inputs
-   `(("guile" ,(specification->package "guile@2.2"))))
+   `(("guile" ,(specification->package "guile@3"))))
   (native-inputs
    `(("autoconf" ,(specification->package "autoconf"))
      ("automake" ,(specification->package "automake"))

configure.ac

@@ -43,7 +43,7 @@ m4_pattern_allow([^GUILE_PKG])
 m4_pattern_allow([^GUILE_PROGS])
 
 # Check for latest Guile development files.
-GUILE_PKG([3.0 2.2 2.0])
+GUILE_PKG([3.0])
 
 # Checks for programs.
 GUILE_PROGS

src/mcron/base.scm

@@ -397,16 +397,16 @@ of CHILDREN-DATA."
   (define (match-collected-pid? job-data)
     (= (job-data:pid job-data) collected-pid))
 
-  (if (and has-children?
+  (cond ((and has-children?
-           (not (= 0 collected-pid)))   ;at least one process was collected
+              (not (= 0 collected-pid)))   ;at least one process was collected
-      (begin
+         (update-number-children! 1-)
-        (update-number-children! 1-)
+         ;; Fully collect the output of the reaped child process.
-        ;; Fully collect the output of the reaped child process.
+         (and=> (find match-collected-pid? children-data)
-        (and=> (find match-collected-pid? children-data)
+                (lambda (child-data)
-               (lambda (child-data)
+                  (process-output (list child-data))))
-                 (process-output (list child-data))))
+         (child-cleanup (remove match-collected-pid? children-data)))
-        (child-cleanup (remove match-collected-pid? children-data)))
+        (else
-      children-data))
+         children-data)))
 
 (define* (run-job-loop #:optional (fd-list '())
                        #:key (schedule %global-schedule))
@@ -423,20 +423,6 @@ infinitum."
   ;; case we break out of the loop here, and let the main procedure deal with
   ;; the situation (it will eventually re-call this function, thus maintaining
   ;; the loop).
-  (cond-expand
-    ((or guile-3.0 guile-2.2)                     ;2.2 and 3.0
-     (define select* select))
-    (else
-     ;; On Guile 2.0, 'select' could throw upon EINTR or EAGAIN.
-     (define (select* read write except time)
-       (catch 'system-error
-         (lambda ()
-           (select read write except time))
-         (lambda args
-           (if (member (system-error-errno args) (list EAGAIN EINTR))
-               '(() () ())
-               (apply throw args)))))))
-
   (let/ec break
     (let loop ((children-data '()))     ;list of <job-data> objects
       (match (find-next-jobs #:schedule schedule)
@@ -452,8 +438,8 @@ infinitum."
                                                   (port->fdes p)))
                                            ports)))
            (when (> sleep-time 0)
-             (match (select* (append fd-list children-fdes)
+             (match (select (append fd-list children-fdes)
-                             '() '() sleep-time)
+                            '() '() sleep-time)
                ((() () ())
                 ;; 'select' returned an empty set, perhaps because it got
                 ;; EINTR or EAGAIN.