On 14.09.2017 08:44, Gary Schneir wrote:
Can anyone provide some assistance to understanding the differences and
a way get a single code base to work in all three environments without
naming the library file?
On Cygwin, libraries are Windows DLL's. That appears to be a
conscious project decision.
The TL;DR is that Windows DLL's are not going to give you the behaviors
of ELF
shared libraries on GNU/Linux. Cygwin would probably have to whip up its
own
shared library format for that, or port one.
The complication doesn't seem worth it.
You can think of dlopen as a wrapper around LoadLibrary, and dlsym doing
GetProcAddress.
In Windows programming, doing GetProcAddress on symbols within an .exe
is something
that isn't normally done; it's not clear that it is supposed to work at
all.
For it to even have any hope of working, the function would have to be
somehow
declared "dllexport" (in Visual C terms).
I think the shared lib building mechanism under Cygwin hides that; there
is no
Visual C __declspec(dllexport) stuff:
See: https://cygwin.com/cygwin-ug-net/dll.html
Still, the toolchain has to be arranging for the equivalent of
__declspec(dllexport)
for the external symbols.
It's probably not configured to do that for the symbols in a regular
executable.
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