libutil: make AutoCloseFD a better resource

add a reset() method to close the wrapped fd instead of assigning magic
constants. also make the from-fd constructor explicit so you can't
accidentally assign the *wrong* magic constant, or even an unrelated
integer that also just happens to be an fd by pure chance.

Change-Id: I51311b0f6e040240886b5103d39d1794a6acc325

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstore/remote-fs-accessor.cc b/src/libstore/remote-fs-accessor.cc
index fcfb527f5..c8e20b3b5 100644
--- a/src/libstore/remote-fs-accessor.cc
+++ b/src/libstore/remote-fs-accessor.cc
@@ -71,7 +71,7 @@ std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_, boo
             auto narAccessor = makeLazyNarAccessor(listing,
                 [cacheFile](uint64_t offset, uint64_t length) {
 
-                    AutoCloseFD fd = open(cacheFile.c_str(), O_RDONLY | O_CLOEXEC);
+                    AutoCloseFD fd{open(cacheFile.c_str(), O_RDONLY | O_CLOEXEC)};
                     if (!fd)
                         throw SysError("opening NAR cache file '%s'", cacheFile);