Fundamental defect of the concept of shared libraries

[Guy Harris]

>>In the proceedings of the Summer 1990 Usenix Conference (Anaheim) there
>>are two papers describing different implementations of shared libraries.
>>Both papers present results.  Both papers conclude that for programs not
>>dominated by startup costs,
>
>Marc Sabatella's paper gives data, 10% for ineffecient coding of library
>and maximum of 10% of start up overhead with reasonably large programs.

Marc Sabatella's paper says that the overhead of PIC is about 10%, and
also notes that since only the libraries are PIC, "this has a negligible
effect on the performance of most programs".  I'm curious whether that
statement is intended to apply to window-system programs or not; I
wouldn't be surprised if they didn't spend more time in library code.

>As I already said, PIC (Position Independent Code) imposes several
>restrictions to hardware, which many architectures can't obey.

Which architectures?  SPARC obviously isn't one of them, and HP-PA
isn't, either, as the HP folks also did their shared libraries on Series
800 machines.  So far, MIPS R-series doesn't seem to be one, either; its
branch instructions are position-independent, and it can do an
unconditional "branch to subroutine", so it can get the PC of the
beginning of the routine into a register with position-independent code.
The Motorola 88K isn't one, either; check out the System V Release 4 ABI
for the 88K.