On Wed, 12 Apr 2017, Bishop via fpc-devel wrote:
I had some fears concerning idea development of "Dynamic packages" in
FreePascal and possible performance penalties of programs from these changes. This why i
start this discussion and try wrote some of my ideas or/and proposal that, as i
think, can help make FreePascal better.
At first I would like to designate a circle of tasks which in principle can
effectively decide by means of system of dynamic packets. Lets remember for what
DLL`s and SO`s was be created. It was for memory saving (by sharing code and
static conts parts from many applications in memory). Now there is so many
memory
even on phones, that this almoust have no sence (its still work for things like
LibC, ZLib and so.). But this kind of libraries better make with C-style
interface (or use COM/CORBA interfaces like in DirectX if it`s realy needed).
Yes, sometimes someone make libraries for C++ only, but it because of a dominant
position of this language. Pascal didn`t have it. So, as i think, dynamic
packages can be usefull only for something like plugin system in editors like
3Ds
Max, Photoshop and etc. But Sven Bart wrote that "Package libraries can however
only be used by a binary compiled with the same compiler as they rely on quite
a bit of compiler magic.", so they be usefull only for projects that target to
have plugins writed in pascal only. I try to say, that there is not so many
situations that we realy need this system. I dont say that we dont need it at
all, no. But disadvantages from this system must no effect on all other
projects.
This why i have some propositions.
Во время моего общения с Sven Barth он писал "With dynamic packages you can
share classes, strings, memory, etc. between the modules (the main binary and the
different package libraries)". Let's look at the most widespread operating
systems. This will be Windows and Unix-family. In Windows every application starts
from ntdll.dll and walk via kernel32.dll and only after that go to
"main"-function in EXE file. So kernel32.dll always loaded. And its already
have not bad
memory manager (Process heap functions group). Why dont use it? It allow share
memory with C code too (and strings with pascal code). Its already exist in
application memory. In Linux if application use shared libraries it use
libdl.so witch need libc.so. So we already have libc heap. As i know in FreeBSD
and
Solaris situation same.
And the second of my proposal it make dynamic packages like 2nd way in compiler
(like it maked in MSVS where we can select link CRT staticaly or dunamicaly).
Add some switch to compiler (and have 2 compiler variants of RTL, now we have
this in RTL source with {$IFDEF FPC_3_0_0} macro) that will allow generate or
not
generate compiler magic for dynamic packages. They need in not so many cases,
but all this indirect memory accesses make all applications slow (memory, first
of all memory latency, in bottleneck of all today computers).
Dynamic Packages will in each case be optional, they will not be not mandatory.
Michael.
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