I completely removed Cygwin from my machine and then installed the
latest version using the defaults, except I asked for the entire
development package.  I wanted a fresh system for Csound5 testing.

The csound-4.23f10gbs.0 distribution builds and installs as expected,
except in one case.  When building with a version of FLTK that does
not use the Cygwin libraries, and making sure that Csound has access
to this libary and compiling it without the Cygwin libraries, I get a
linking error that never occured before.  Something about _atexit
being defined twice.  Worse yet, -lcygwin appears in the link command!

I don't know what's going on, but I thought I would warn you about
this. 

John

------------------------------- nohup.out --------------------------
...
/bin/bash ../libtool --mode=link gcc  -mno-cygwin -Wall
-falign-loops=4 -falign-jumps=4 -ffast-math -fomit-frame-pointer
-finline-functions -funroll-loops
-I/home/Administrator/opt/fltk/include -mwindows -DWIN32 -mno-cygwin
-mno-cygwin -o
csound.exe -mconsole ccsound.o libcsound.la
-L/home/Administrator/opt/fltk/lib -mwindows -lfltk -lole32 -luuid
-lcomctl32 -lwsock32 -lsupc++ -lstdc++ -lpthread
 -lwinmm
libtool: link: warning: library `/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/../../../libstdc++.la' was moved.
libtool: link: warning: library `/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/../../../libstdc++.la' was moved.
gcc -mno-cygwin -Wall -falign-loops=4 -falign-jumps=4 -ffast-math
-fomit-frame-pointer -finline-functions -funroll-loops
-I/home/Administrator/opt/fltk/include
-mwindows -DWIN32 -mno-cygwin -mno-cygwin -o csound.exe -mconsole
ccsound.o -mwindows  ./.libs/libcsound.a
-L/home/Administrator/opt/fltk/lib
-L/GCC/gcc-3.3.1-3/.build/i686-pc-cygwin/libstdc++-v3/src
-L/GCC/gcc-3.3.1-3/.build/i686-pc-cygwin/libstdc++-v3/src/.libs
-L/GCC/gcc-3.3.1-3/.build/gcc -L/usr/i686-pc-cygwin/bin
-L/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1
-L/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/../../.. -lfltk -lole32 -luuid
-lcomctl32 -lwsock32 /usr/lib/./libsupc++.a
/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/../../../libstdc++.a -lcygwin
-luser32 -lkernel32 -ladvapi32 -lshell32 -lgcc -lpthread -lwinmm
/usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/../../../libcygwin.a(d000675.o)(.text+0x0):
multiple definition of `_atexit'
/usr/lib/gcc-lib/i686-pc-mingw32/3.3.1/../../../../i686-pc-mingw32/lib/crt2.o(.text+0x270):crt1.c:
first defined here
collect2: ld returned 1 exit status
make[2]: *** [csound.exe] Error 1