[augeas-devel] [Augeas] #123: unref of static value causes segfault

[Augeas]

#123: unref of static value causes segfault
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  Reporter:  fgiraldeau  |       Owner:  lutter
      Type:  defect      |      Status:  new   
  Priority:  minor       |   Milestone:  next  
 Component:  Augeas      |     Version:  0.7.0 
Resolution:              |    Keywords:        
-------------------------+--------------------------------------------------
Comment (by fgiraldeau):

 Function exn_error creates a static const value:
 {{{
 struct value *exn_error(void) {
     static const struct exn exn = {
         .info = NULL, .seen = 1, .error = 1,
         .message = (char *) "Error during evaluation",
         .nlines = 0, .lines = NULL };
     static const struct value value = {
         .ref = REF_MAX, /* Protect against being freed */
         .info = NULL, .tag = V_EXN,
         { .exn = (struct exn *) &exn } };
     return (struct value *) &value;
 }
 }}}

 And macro unref tries to always assign 0 to value->info

 {{{
 #define unref(s, t)                                                     \
     do {                                                                \
         if ((s) != NULL && (s)->ref != REF_MAX) {                       \
             assert((s)->ref > 0);                                       \
             if (--(s)->ref == 0) {                                      \
                 /*memset(s, 255, sizeof(*s));*/                         \
                 free_##t(s);                                            \
             }                                                           \
         }                                                               \
         (s) = NULL;                                                     \
     } while(0)
 }}}

 Could we assign the value only if it's not yet 0?

-- 
Ticket URL: <https://fedorahosted.org/augeas/ticket/123#comment:6>
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