From e845d19ae368cb9ee6371c4b2fdbdc86a110d893 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Fri, 9 Oct 2020 17:54:59 +0200
Subject: [PATCH] Remove Lazy

This fixes a crash during startup when compiling Nix as a single
compilation unit.
---
 src/libutil/lazy.hh | 48 ---------------------------------------------
 src/libutil/util.cc | 34 +++++++++++++++++---------------
 2 files changed, 18 insertions(+), 64 deletions(-)
 delete mode 100644 src/libutil/lazy.hh

diff --git a/src/libutil/lazy.hh b/src/libutil/lazy.hh
deleted file mode 100644
index d073e486c..000000000
--- a/src/libutil/lazy.hh
+++ /dev/null
@@ -1,48 +0,0 @@
-#include <exception>
-#include <functional>
-#include <mutex>
-
-namespace nix {
-
-/* A helper class for lazily-initialized variables.
-
-     Lazy<T> var([]() { return value; });
-
-   declares a variable of type T that is initialized to 'value' (in a
-   thread-safe way) on first use, that is, when var() is first
-   called. If the initialiser code throws an exception, then all
-   subsequent calls to var() will rethrow that exception. */
-template<typename T>
-class Lazy
-{
-
-    typedef std::function<T()> Init;
-
-    Init init;
-
-    std::once_flag done;
-
-    T value;
-
-    std::exception_ptr ex;
-
-public:
-
-    Lazy(Init init) : init(init)
-    { }
-
-    const T & operator () ()
-    {
-        std::call_once(done, [&]() {
-            try {
-                value = init();
-            } catch (...) {
-                ex = std::current_exception();
-            }
-        });
-        if (ex) std::rethrow_exception(ex);
-        return value;
-    }
-};
-
-}
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 1a8873136..9804e9a51 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1,4 +1,3 @@
-#include "lazy.hh"
 #include "util.hh"
 #include "affinity.hh"
 #include "sync.hh"
@@ -522,21 +521,24 @@ std::string getUserName()
 }
 
 
-static Lazy<Path> getHome2([]() {
-    auto homeDir = getEnv("HOME");
-    if (!homeDir) {
-        std::vector<char> buf(16384);
-        struct passwd pwbuf;
-        struct passwd * pw;
-        if (getpwuid_r(geteuid(), &pwbuf, buf.data(), buf.size(), &pw) != 0
-            || !pw || !pw->pw_dir || !pw->pw_dir[0])
-            throw Error("cannot determine user's home directory");
-        homeDir = pw->pw_dir;
-    }
-    return *homeDir;
-});
-
-Path getHome() { return getHome2(); }
+Path getHome()
+{
+    static Path homeDir = []()
+    {
+        auto homeDir = getEnv("HOME");
+        if (!homeDir) {
+            std::vector<char> buf(16384);
+            struct passwd pwbuf;
+            struct passwd * pw;
+            if (getpwuid_r(geteuid(), &pwbuf, buf.data(), buf.size(), &pw) != 0
+                || !pw || !pw->pw_dir || !pw->pw_dir[0])
+                throw Error("cannot determine user's home directory");
+            homeDir = pw->pw_dir;
+        }
+        return *homeDir;
+    }();
+    return homeDir;
+}
 
 
 Path getCacheDir()