fuse-7z-ng: add patch to zero-init struct fuse_operations

Fixes segfault when reading archive files.

`struct fuse_operations` contains function pointers specifying a
filesystem's behavior for each operation. For unimplemented operations,
they must be set to null so that libfuse can fall back to a default
implementation or return an error. In fuse-7z-ng, however, they were
left uninitialized, causing segfault due to garbage values stored in
them.

pkgs/tools/filesystems/fuse-7z-ng/default.nix

@@ -14,6 +14,9 @@ stdenv.mkDerivation rec {
     # Drop unused pthread library. pthread_yield()
     # fails the configure.
     ./no-pthread.patch
+    # Zero-initialize unset fields of `struct fuse_operations` so that
+    # garbage values don't cause segfault.
+    ./zero-init-fuse-operations.patch
   ];
 
   nativeBuildInputs = [ pkg-config makeWrapper autoconf automake ];

pkgs/tools/filesystems/fuse-7z-ng/zero-init-fuse-operations.patch

@@ -0,0 +1,12 @@
+Zero-initialize unset fields of `struct fuse_operations`.
+--- a/src/main.cpp
++++ b/src/main.cpp
+@@ -195,7 +195,7 @@ main (int argc, char **argv)
+         mkdir(param.mountpoint, 0750);
+     }
+ 
+-    struct fuse_operations fuse7z_oper;
++    struct fuse_operations fuse7z_oper = {0};
+     fuse7z_oper.init = fuse7z_init;
+     fuse7z_oper.destroy = fuse7z_destroy;
+     fuse7z_oper.readdir = fuse7z_readdir;