nix run: Fix segfault on macOS

Note that clearenv() is not available on macOS.

Fixes #1907.

2 files changed, 10 insertions, 0 deletions

diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 341dedfdf038..2391e14a94bd 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -73,6 +73,13 @@ std::map<std::string, std::string> getEnv()
 }
 
 
+void clearEnv()
+{
+    for (auto & name : getEnv())
+        unsetenv(name.first.c_str());
+}
+
+
 Path absPath(Path path, Path dir)
 {
     if (path[0] != '/') {
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 47e02bc898a6..c5c537ee63d8 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -32,6 +32,9 @@ string getEnv(const string & key, const string & def = "");
 /* Get the entire environment. */
 std::map<std::string, std::string> getEnv();
 
+/* Clear the environment. */
+void clearEnv();
+
 /* Return an absolutized path, resolving paths relative to the
    specified directory, or the current directory otherwise.  The path
    is also canonicalised. */