Pyxplot segfaults immediately in Ventura #10

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1. kencu commented on Jan 8, 2023

   

   kencu

   on Jan 8, 2023

   Last edited by kencu

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   the function ppl_unixGetHomeDir seems to be returning NULL on Ventura, resulting in the crash.

   This doesn't fix the function, but avoids the crash, at least:

   % cat patch-pyxplot-no-crash-ventura.diff
   --- ./src/settings/settingsInit.c.orig	2023-01-07 16:41:23
   +++ ./src/settings/settingsInit.c	2023-01-07 16:41:31
   @@ -364,7 +364,14 @@
      se->session_default.color_rep= SW_TERMCOL_GRN;
      se->session_default.color_wrn= SW_TERMCOL_BRN;
      se->session_default.color_err= SW_TERMCOL_RED;
   -  strcpy(se->session_default.homedir, ppl_unixGetHomeDir(&context->errcontext));
   +
   +  char  *myhomedir;
   +  myhomedir = ppl_unixGetHomeDir(&context->errcontext);
   +  if (myhomedir == NULL) {
   +  	myhomedir = "~";
   +  }
   +  strncpy(se->session_default.homedir,myhomedir,4096);
   +  //strcpy(se->session_default.homedir, ppl_unixGetHomeDir(&context->errcontext));
    
      // Estimate the machine precision of the floating point unit we are using
      ppl_makeMachineEpsilon();
   
2. kencu commented on Jan 11, 2023

   

   kencu

   on Jan 11, 2023

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   this problem is in the way this function works:

   struct passwd *UnixGetPwEntry(pplerr_context *context)
    {
     int uid;
     struct passwd *ptr;
   
     uid = getuid();
     setpwent(); // Memory leak which valgrind reveals here is probably okay; getpwent sets up a static variable with malloc
     while ((ptr = getpwent()) != NULL)
      if (ptr->pw_uid == uid) break;
     endpwent();
     return(ptr);
    }
   

   calling endpwent(); is clearing the ptr before returning it, resulting in the NULL:

   adding this:

     printf("these are findings before endpwent: userid = %d, homedir = %s\n", ptr->pw_uid, ptr->pw_dir);
     endpwent();
     printf("these are findings after endpwent: userid = %d, homedir = %s\n", ptr->pw_uid, ptr->pw_dir);
     
     return(ptr);
   

   we see:

   % ./a.out     
   these are findings before endpwent: userid = 501, homedir = /Users/myusername
   these are findings after endpwent: userid = 0, homedir = (null)
   

   there are several ways this might be fixed, but one way is to use a different function to find pw entry:

   char *ppl_unixGetHomeDir(pplerr_context *context)
    {
     struct passwd *ptr;
     static char   *failover=NULL;
   
   //  ptr = UnixGetPwEntry(context);
   
     //use this function instead
     ptr = getpwuid(getuid());