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, 2 insertions, 2 deletions

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index bd9be52f3..20519c1a2 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -549,7 +549,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
             if (fds[1].revents) {
                 /* Accept a new connection. */
                 assert(fds[1].revents & POLLIN);
-                AutoCloseFD fdClient = accept(fdServer.get(), nullptr, nullptr);
+                AutoCloseFD fdClient{accept(fdServer.get(), nullptr, nullptr)};
                 if (!fdClient) continue;
 
                 debug("GC roots server accepted new client");
@@ -647,7 +647,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
            by another process. We need to be sure that we can acquire an
            exclusive lock before deleting them. */
         if (baseName.find("tmp-", 0) == 0) {
-            AutoCloseFD tmpDirFd = open(realPath.c_str(), O_RDONLY | O_DIRECTORY);
+            AutoCloseFD tmpDirFd{open(realPath.c_str(), O_RDONLY | O_DIRECTORY)};
             if (tmpDirFd.get() == -1 || !lockFile(tmpDirFd.get(), ltWrite, false)) {
                 debug("skipping locked tempdir '%s'", realPath);
                 return;