Your syntax is correct; the gotcha here is a bit of weirdness with Cygwin's view of the filesystem.
In Cygwin, the root directory
/ points to what, in the Windows filesystem, is the root of your Cygwin install, which is usually
c:\cygwin. To access anything outside that, you canonically have to use
/cygdrive/[drive letter]; for example, the
c:\windows\system32 directory's path within Cygwin is not
/c/windows/system32 but rather
A common way of circumventing this annoyance is to create symlinks in
/ which point to various drive letters in
ln -s /cygdrive/c /c; if you're able to access files outside the Cygwin root with paths such as
/c/windows/..., it's because such symlinks exist, whether created by hand or automatically.
This scheme works well for most purposes, but not all programs automatically follow symlinks, and
find is such a program;
find /c/strawberry/ ... works because you're starting
find off on the 'far' side of the symlink, but
find / ... doesn't because it starts out on the 'near' side and won't by default follow the
/c symlink. To produce the desired behavior, pass the
-L option to find;
find -L / -name libstdc++-6.dll should turn up the same results as
find /c/strawberry -name libstdc++-6.dll will.