From a5a611496aa06ce04fe4a4411cdafbf5ab8e8ec6 Mon Sep 17 00:00:00 2001
From: Christopher Dykes <cdykes@fb.com>
Date: Tue, 11 Apr 2017 12:26:53 -0700
Subject: [PATCH] Implement clearenv in the portability headers

Summary:
It doesn't exist on OSX or Windows, so implement it.

Closes https://github.com/facebook/folly/issues/567

Reviewed By: yfeldblum

Differential Revision: D4783463

fbshipit-source-id: 0a2586aced7123b797a8e55a3e86124b449634e4
---
 folly/portability/Stdlib.cpp | 27 +++++++++++++++++++++++++++
 folly/portability/Stdlib.h   |  4 ++++
 2 files changed, 31 insertions(+)

diff --git a/folly/portability/Stdlib.cpp b/folly/portability/Stdlib.cpp
index 013a7d32..e790a3ea 100644
--- a/folly/portability/Stdlib.cpp
+++ b/folly/portability/Stdlib.cpp
@@ -136,3 +136,30 @@ int unsetenv(const char* name) {
 }
 }
 #endif
+
+#if !__linux__ && !FOLLY_MOBILE
+#include <string>
+#include <vector>
+
+extern "C" int clearenv() {
+  std::vector<std::string> data;
+  for (auto it = environ; it && *it; ++it) {
+    std::string entry(*it);
+    auto equalsPosition = entry.find('=');
+    if (equalsPosition == std::string::npos || equalsPosition == 0) {
+      // It's either a drive setting (if on Windows), or something clowny is
+      // going on in the environment.
+      continue;
+    } else {
+      data.emplace_back(entry.substr(0, equalsPosition));
+    }
+  }
+
+  for (auto s : data) {
+    if (unsetenv(s.c_str()) != 0)
+      return -1;
+  }
+
+  return 0;
+}
+#endif
diff --git a/folly/portability/Stdlib.h b/folly/portability/Stdlib.h
index 333453da..1124273b 100644
--- a/folly/portability/Stdlib.h
+++ b/folly/portability/Stdlib.h
@@ -47,4 +47,8 @@ char*** _NSGetEnviron(void);
 #endif
 #define environ (*_NSGetEnviron())
 #endif
+
+#if !__linux__ && !FOLLY_MOBILE
+int clearenv();
+#endif
 }
-- 
2.34.1