Re: GNAT Executables: How low can you go?

[ok@goanna.cs.rmit.edu.au (Richard A. O'Keefe)]

"Theodore E. Dennison" <dennison@escmail.orl.mmc.com> writes:

>Michael F Brenner wrote:
>> 
>> There is no need to justify tiny executables, 140K is a Bloated hello-world.

>Its still 140K, just in two different files.


Wrong.  Suppose the library is 120 k and the application, minus library,
is 20k.

- static linking:
    you get 140k in your program AND YOU STILL HAVE THE LIBRARY
    so you have one 120k file and one 140k file

- dynamic linking
    you have one one 120k file and one 20k file.

The model I have here is someone developing on a UNIX box; I can't throw
away the original copy of the (statically linked) library just because I
have compiled one program!  Come to think of it, the same is true with
DOS compilers:  just because I've compiled one program doesn't mean I can
throw the library away.

1.  Development time.
    Dynamic linking saves space _even with only one program_.
    (In this example, 140k -vs- 260k.)

2.  Shipping.
    Any dynamic library that doesn't come standard with the operating
    system has to be shipped with the program that uses it.
    Shipping the DLL with the EXE may take _more_ space than shipping
    the statically linked version, because the DLL includes things
    that this particular EXE may not need.

    However, if the shipping package includes several applications using
    the same DLL, only one copy is needed, and it's really quite common
    to have several applications in one package.  (DOS example:  command
    line compiler, IDE compiler, linker.)

3.  Installation.
    The user only has to install *one* copy of the DLL; the installation
    process has to recognise whether the DLL has already been installed.

4.  Run time.
    The DLL will be loaded only once no matter how many applications are
    using it (UNIX "shared" libraries), and may, depending on the operating
    system, be kept around for a little while after the last application
    using it has quit so that it doesn't need reloading (like the old UNIX
    "save text" bit).


-- 
Abigail Ruth, born 8 April 1996, 7lbs, wonderful!
Richard A. O'Keefe; http://www.cs.rmit.edu.au/~ok; RMIT Comp.Sci.