Re: C Strings in Ada?

[adoyle@bbn.com (Allan Doyle)]

Whew, the nesting is getting too deep. I sliced out the parts I want to
comment on...

>>What is the best way to represent C_Strings in Ada?  

>$$	procedure to_c (str : string) 
>$$	is
>$$	  procedure c_routine (addr : system.address);
>$$          pragma interface (C, c_routine);	-- (void) c_routine(s)
>$$						-- char * s;
>$$	  c_string : constant string := str & Ascii.NUL;
>$$	begin
>$$	  c_routine(c_string(c_string'first)'address);
>$$	end to_c;

>I dont think this solution *requires* heap allocation.  A good compiler would 
>be free to use stack space for the C strings in these cases, both for
>the local constant c_string and for the return value.  Of course, there is 
>the overhead of copying the strings but the allocation can be relatively
>cheap.
>
>-----------------------------------------------------------------------
>Alex Blakemore                       Internet: blakemore@software.org
>Software Productivity Consortium     UUNET:    ...!uunet!software!blakemore
>2214 Rock Hill Rd, Herndon VA 22070  Bellnet:  (703) 742-7125

Judging from the replies about heap space, I'm getting a little worried.
Do you guys mean to tell me that it's compiler dependent how to allocate
the 'c_string' constant? This is just the sort of thing that makes me
mistrust Ada for a realtime application that has to run for a long time
without any memory leaks. If I take the worst case assumption that c_string
is being allocated from the heap and add it to the worst case assumption
that my Ada run-time will not be doing garbage collection (perfectly legal,
I understand), then how many of these little beasties can I convert from
Ada to C before I run out of memory?



Allan Doyle                                        adoyle@bbn.com
BBN Systems and Technologies Corporation           (617) 873-3398
70 Fawcett Street,   Cambridge, MA 02138