I like the idea that vid has of making a portable library in FASM that can be used in both Windows and Linux. What I have put together as a test piece is a set of module I pinched fom the masm32 library, (mainly string procedures), ported them to FASM and then built them using the MINGW utility AR.EXE. FASM runs on both platforms and AR.EXE should also do this so the test library using this tecnique may not be a lot of work to make truly portable between both platforms.
http://www.masm32.com/files/fasm32.zip
nice, thanks for pointing out the "ar" utility.
but i think you won't have it THAT easy. I bet the linux files would have to be ELF, not MS-COFF. And i don't which is linux library format.
Probaby the Linux version would be built with different file names but the info I found on the internet to build libraries with AR.EXE probably applies to to Linux as well as Windows so as long as FASM can properly build ELF format object modules, I can't see a problem making a portable library that just needs to be assembled on each platform and then built as a library.