[Chicken-janitors] #999: Unit ports uses read-string! from unit extras, causing errors (segfaults) in programs that only (use ports)

[Chicken Trac]

#999: Unit ports uses read-string! from unit extras, causing errors (segfaults)
in programs that only (use ports)
----------------------------+-----------------------------------------------
 Reporter:  sjamaan         |       Owner:  felix  
     Type:  defect          |      Status:  new    
 Priority:  major           |   Milestone:  someday
Component:  core libraries  |     Version:  4.8.x  
 Keywords:                  |  
----------------------------+-----------------------------------------------
 On IRC, user "szablica" pointed out that the following program will cause
 a segfault when run in compiled mode:

 {{{
 #!scm
 (use ports)

 (define (read-file-contents filename)
   (call-with-output-string
     (lambda (result-string)
       (call-with-input-file
         filename
         (lambda (source-file)
           (copy-port source-file result-string))))))

 (display (read-file-contents "/etc/hosts"))
 }}}

 If you run it with a Chicken built with DEBUGBUILD=1, you'll get a decent
 error message:

 {{{
 Error: unbound variable: read-string!

         Call history:

         foo.scm:11: read-file-contents
         foo.scm:4: call-with-output-string
         foo.scm:6: call-with-input-file
         foo.scm:9: copy-port            <--
 }}}

 It works fine from csi.  The reason this doesn't work is that {{{read-
 string!}}} is provded by unit extras, but ports doesn't depend on it.
 Simply adding {{{(uses extras)}}} to the declarations causes the problem
 to go away, but AFAICT, this is iffy: extras already declares {{{(uses
 ports)}}} so this would mean we've introduced a circular dependency.

 I think such implicit dependencies could be easily prevented by converting
 core to use proper modules, and getting rid of the "unit" concept, but I
 don't know if that's feasible.

-- 
Ticket URL: <http://bugs.call-cc.org/ticket/999>
Chicken Scheme <http://www.call-with-current-continuation.org/>
Chicken Scheme is a compiler for the Scheme programming language.