From: John Carter <john.carter@...>
Date: 2008-06-30T10:19:36+09:00
Subject: BUG: Ruby 1.8.7 - io.c Argument Error in syscall,"string contains 	null byte"

I have opened this as bug...
   http://rubyforge.org/tracker/index.php?func=detail&aid=20895&group_id=426&atid=1698


The following snippet invokes the statfs64 syscall.
bug.rb================================================================
string = " "* 84
p syscall( 268, "/", string.size, string)
string = "\0"* 84
p syscall( 268, "/", string.size, string)
======================================================================

If I run this under ruby 1.8.6, both invocations work.

If I run this under ruby 1.8.7, the second one fails with...
ruby  -w bug.rb
0
bug.rb:4:in `syscall': string contains null byte (ArgumentError)
 	from bug.rb:4

The reason is in ruby-1.8.7-p22/io.c in the function rb_f_syscall
there is this code....

 	if (!NIL_P(v)) {
 	    StringValue(v);
 	    rb_str_modify(v);
 	    arg[i] = (unsigned long)StringValueCStr(v);
 	}

In ruby 1.8.6 is was

 	if (!NIL_P(v)) {
 	    StringValue(v);
 	    rb_str_modify(v);
 	    arg[i] = (unsigned long)RSTRING(v)->ptr;
 	}

The macro StringValueCStr is defined in ruby.h as....
   #define StringValueCStr(v) rb_string_value_cstr(&(v))

The function rb_string_value_cstr is defined in string.c as ....

rb_string_value_cstr(ptr)
     volatile VALUE *ptr;
{
     VALUE str = rb_string_value(ptr);
     char *s = RSTRING(str)->ptr;

     if (!s || RSTRING(str)->len != strlen(s)) {
 	rb_raise(rb_eArgError, "string contains null byte");
     }
     return s;
}

I believe the original 1.8.6 implementation was correct and this
particular changed should be rolled back.

Thanks.



John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand