String_make problems

[Simon Glover]

 Currently, whenever we create a new string with a call to string_make,
 we allocate the memory for it by a simple call to malloc (via
 mem_sys_allocate in memory.c). However, we don't check the return value
 of this call, so if the malloc fails, Parrot promptly segfaults
 when we try to make the string null-terminated. For example,
 the code 

        set S0, "a"
        repeat S0, S0, 2000000000
        end      

 invariably causes Parrot to segfault on my machine. What's the best way
 to fix this? 

 Simon