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+# FUSE {#sec-fuse}
+
+Some packages rely on
+[FUSE](https://www.kernel.org/doc/html/latest/filesystems/fuse.html) to provide
+support for additional filesystems not supported by the kernel.
+
+In general, FUSE software are primarily developed for Linux but many of them can
+also run on macOS. Nixpkgs supports FUSE packages on macOS, but it requires
+[macFUSE](https://osxfuse.github.io) to be installed outside of Nix. macFUSE
+currently isn't packaged in Nixpkgs mainly because it includes a kernel
+extension, which isn't supported by Nix outside of NixOS.
+
+If a package fails to run on macOS with an error message similar to the
+following, it's a likely sign that you need to have macFUSE installed.
+
+    dyld: Library not loaded: /usr/local/lib/libfuse.2.dylib
+    Referenced from: /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs
+    Reason: image not found
+    [1]    92299 abort      /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs
+
+Package maintainers may often encounter the following error when building FUSE
+packages on macOS:
+
+    checking for fuse.h... no
+    configure: error: No fuse.h found.
+
+This happens on autoconf based projects that use `AC_CHECK_HEADERS` or
+`AC_CHECK_LIBS` to detect libfuse, and will occur even when the `fuse` package
+is included in `buildInputs`. It happens because libfuse headers throw an error
+on macOS if the `FUSE_USE_VERSION` macro is undefined. Many projects do define
+`FUSE_USE_VERSION`, but only inside C source files. This results in the above
+error at configure time because the configure script would attempt to compile
+sample FUSE programs without defining `FUSE_USE_VERSION`.
+
+There are two possible solutions for this problem in Nixpkgs:
+
+1. Pass `FUSE_USE_VERSION` to the configure script by adding
+   `CFLAGS=-DFUSE_USE_VERSION=25` in `configureFlags`. The actual value would
+   have to match the definition used in the upstream source code.
+2. Remove `AC_CHECK_HEADERS` / `AC_CHECK_LIBS` for libfuse.
+
+However, a better solution might be to fix the build script upstream to use
+`PKG_CHECK_MODULES` instead. This approach wouldn't suffer from the problem that
+`AC_CHECK_HEADERS`/`AC_CHECK_LIBS` has at the price of introducing a dependency
+on pkg-config.