diff --git a/hphp/compiler/package.cpp b/hphp/compiler/package.cpp
index 7dfbe94f7..35c627f6d 100644
--- a/hphp/compiler/package.cpp
+++ b/hphp/compiler/package.cpp
@@ -19,6 +19,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <dirent.h>
+#include "folly/String.h"
 #include "hphp/compiler/analysis/analysis_result.h"
 #include "hphp/compiler/parser/parser.h"
 #include "hphp/compiler/analysis/symbol_table.h"
@@ -67,7 +68,7 @@ void Package::addInputList(const char *listFileName) {
   FILE *f = fopen(listFileName, "r");
   if (f == nullptr) {
     throw Exception("Unable to open %s: %s", listFileName,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
   char fileName[PATH_MAX];
   while (fgets(fileName, sizeof(fileName), f)) {
diff --git a/hphp/runtime/base/exceptions.h b/hphp/runtime/base/exceptions.h
index 1b190c7cb..542791d57 100644
--- a/hphp/runtime/base/exceptions.h
+++ b/hphp/runtime/base/exceptions.h
@@ -20,6 +20,7 @@
 #include "hphp/util/exception.h"
 #include "hphp/util/util.h"
 #include "hphp/runtime/base/types.h"
+#include "folly/String.h"
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -173,7 +174,7 @@ class SystemCallFailure : public ExtendedException {
 public:
   explicit SystemCallFailure(const char *func)
     : ExtendedException("%s returned %d: %s.", func, errno,
-                        Util::safe_strerror(errno).c_str()) {}
+                        folly::errnoStr(errno).c_str()) {}
   virtual ~SystemCallFailure() throw() {}
   EXCEPTION_COMMON_IMPL(SystemCallFailure);
 };
diff --git a/hphp/runtime/base/file.cpp b/hphp/runtime/base/file.cpp
index 082b7ab65..70af8a750 100644
--- a/hphp/runtime/base/file.cpp
+++ b/hphp/runtime/base/file.cpp
@@ -30,9 +30,11 @@
 #include "hphp/runtime/base/zend-string.h"
 #include "hphp/runtime/base/zend-printf.h"
 #include "hphp/runtime/base/exceptions.h"
-#include <sys/file.h>
 #include "hphp/runtime/base/array-iterator.h"
 #include "hphp/runtime/base/stream-wrapper-registry.h"
+#include "folly/String.h"
+
+#include <sys/file.h>
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -776,7 +778,7 @@ Array File::readCSV(int64_t length /* = 0 */, char delimiter_char /* = ',' */,
 }
 
 String File::getLastError() {
-  return Util::safe_strerror(errno);
+  return String(folly::errnoStr(errno).toStdString());
 }
 
 
diff --git a/hphp/runtime/base/hardware-counter.cpp b/hphp/runtime/base/hardware-counter.cpp
index b1b8c33e1..9908a9205 100644
--- a/hphp/runtime/base/hardware-counter.cpp
+++ b/hphp/runtime/base/hardware-counter.cpp
@@ -37,6 +37,7 @@
 #include "hphp/runtime/base/zend-url.h"
 #include "hphp/runtime/base/runtime-option.h"
 #include "hphp/runtime/vm/jit/translator-x64.h"
+#include "folly/String.h"
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -76,13 +77,13 @@ public:
     m_fd = syscall(__NR_perf_event_open, &pe, 0, -1, -1, 0);
     if (m_fd < 0) {
       Logger::Verbose("perf_event_open failed with: %s",
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
       m_err = -1;
       return;
     }
     if (ioctl(m_fd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
       Logger::Warning("perf_event failed to enable: %s",
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
       close();
       m_err = -1;
       return;
@@ -128,7 +129,7 @@ public:
   void reset() {
     if (m_fd > 0 && ioctl (m_fd, PERF_EVENT_IOC_RESET, 0) < 0) {
       Logger::Warning("perf_event failed to reset with: %s",
-          Util::safe_strerror(errno).c_str());
+          folly::errnoStr(errno).c_str());
       m_err = -1;
     }
   }
diff --git a/hphp/runtime/base/runtime-option.cpp b/hphp/runtime/base/runtime-option.cpp
index 2f0640778..514de30bc 100644
--- a/hphp/runtime/base/runtime-option.cpp
+++ b/hphp/runtime/base/runtime-option.cpp
@@ -41,6 +41,7 @@
 #include "hphp/util/parser/scanner.h"
 #include "hphp/runtime/server/access_log.h"
 #include "hphp/runtime/base/crash-reporter.h"
+#include "folly/String.h"
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -473,7 +474,7 @@ static void setResourceLimit(int resource, Hdf rlimit, const char *nodeName) {
     if (ret) {
       Logger::Error("Unable to set %s to %" PRId64 ": %s (%d)",
                     nodeName, (int64_t)rl.rlim_cur,
-                    Util::safe_strerror(errno).c_str(), errno);
+                    folly::errnoStr(errno).c_str(), errno);
     }
   }
 }
diff --git a/hphp/runtime/base/socket.h b/hphp/runtime/base/socket.h
index 8cac40010..af6c010d0 100644
--- a/hphp/runtime/base/socket.h
+++ b/hphp/runtime/base/socket.h
@@ -24,7 +24,7 @@
 #define SOCKET_ERROR(sock, msg, errn)                           \
   sock->setError(errn);                                         \
   raise_warning("%s [%d]: %s", msg, errn,                       \
-                  Util::safe_strerror(errn).c_str())            \
+                  folly::errnoStr(errn).c_str())                \
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/hphp/runtime/base/ssl-socket.cpp b/hphp/runtime/base/ssl-socket.cpp
index cb92e7e89..4c51e9f20 100644
--- a/hphp/runtime/base/ssl-socket.cpp
+++ b/hphp/runtime/base/ssl-socket.cpp
@@ -18,6 +18,7 @@
 #include "hphp/runtime/base/complex-types.h"
 #include "hphp/runtime/base/runtime-error.h"
 #include "hphp/util/util.h"
+#include "folly/String.h"
 #include <poll.h>
 
 namespace HPHP {
@@ -265,8 +266,7 @@ bool SSLSocket::handleError(int64_t nr_bytes, bool is_init) {
         m_eof = true;
         retry = false;
       } else {
-        string estr = Util::safe_strerror(errno);
-        raise_warning("SSL: %s", estr.c_str());
+        raise_warning("SSL: %s", folly::errnoStr(errno).c_str());
         retry = false;
       }
       break;
diff --git a/hphp/runtime/base/thread-info.cpp b/hphp/runtime/base/thread-info.cpp
index aec22c1f8..ee4996eac 100644
--- a/hphp/runtime/base/thread-info.cpp
+++ b/hphp/runtime/base/thread-info.cpp
@@ -20,6 +20,7 @@
 #include "hphp/runtime/vm/jit/target-cache.h"
 #include "hphp/util/lock.h"
 #include "hphp/util/alloc.h"
+#include "folly/String.h"
 
 #include <sys/mman.h>
 
@@ -170,7 +171,7 @@ void RequestInjectionData::setTimeout(int seconds) {
     sev.sigev_signo = SIGVTALRM;
     sev.sigev_value.sival_ptr = this;
     if (timer_create(CLOCK_REALTIME, &sev, &m_timer_id)) {
-      raise_error("Failed to set timeout: %s", strerror(errno));
+      raise_error("Failed to set timeout: %s", folly::errnoStr(errno).c_str());
     }
     m_hasTimer = true;
   }
diff --git a/hphp/runtime/ext/ext_bzip2.cpp b/hphp/runtime/ext/ext_bzip2.cpp
index 3f4abed18..31ba63814 100644
--- a/hphp/runtime/ext/ext_bzip2.cpp
+++ b/hphp/runtime/ext/ext_bzip2.cpp
@@ -18,6 +18,7 @@
 #include "hphp/runtime/ext/ext_bzip2.h"
 #include "hphp/runtime/base/bzip2-file.h"
 #include "hphp/util/alloc.h"
+#include "folly/String.h"
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -53,7 +54,7 @@ Variant f_bzopen(CVarRef filename, CStrRef mode) {
     bz = NEWOBJ(BZ2File)();
     bool ret = bz->open(File::TranslatePath(filename.toString()), mode);
     if (!ret) {
-      raise_warning("%s", Util::safe_strerror(errno).c_str());
+      raise_warning("%s", folly::errnoStr(errno).c_str());
       return false;
     }
   } else {
diff --git a/hphp/runtime/ext/ext_fb.cpp b/hphp/runtime/ext/ext_fb.cpp
index 92855cd43..8d316c29f 100644
--- a/hphp/runtime/ext/ext_fb.cpp
+++ b/hphp/runtime/ext/ext_fb.cpp
@@ -21,6 +21,7 @@
 #include "hphp/util/db_conn.h"
 #include "hphp/util/logger.h"
 #include "hphp/runtime/base/stat-cache.h"
+#include "folly/String.h"
 #include "netinet/in.h"
 #include "hphp/runtime/base/externals.h"
 #include "hphp/runtime/base/string-util.h"
@@ -1494,7 +1495,7 @@ static Variant do_lazy_stat(Function dostat, CStrRef filename) {
   struct stat sb;
   if (dostat(File::TranslatePathWithFileCache(filename).c_str(), &sb)) {
     Logger::Verbose("%s/%d: %s", __FUNCTION__, __LINE__,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
   return stat_impl(&sb);
diff --git a/hphp/runtime/ext/ext_file.cpp b/hphp/runtime/ext/ext_file.cpp
index c81e2db42..1be22a093 100644
--- a/hphp/runtime/ext/ext_file.cpp
+++ b/hphp/runtime/ext/ext_file.cpp
@@ -35,6 +35,7 @@
 #include "hphp/util/logger.h"
 #include "hphp/util/util.h"
 #include "hphp/util/process.h"
+#include "folly/String.h"
 #include <dirent.h>
 #include <glob.h>
 #include <sys/types.h>
@@ -59,7 +60,7 @@
 #define CHECK_SYSTEM(exp)                                 \
   if ((exp) != 0) {                                       \
     Logger::Verbose("%s/%d: %s", __FUNCTION__, __LINE__,  \
-                    Util::safe_strerror(errno).c_str());  \
+                    folly::errnoStr(errno).c_str());      \
     return false;                                         \
   }                                                       \
 
@@ -92,7 +93,7 @@ namespace HPHP {
 static bool check_error(const char *function, int line, bool ret) {
   if (!ret) {
     Logger::Verbose("%s/%d: %s", function, line,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
   return ret;
 }
@@ -541,7 +542,7 @@ Variant f_readfile(CStrRef filename, bool use_include_path /* = false */,
   Variant f = f_fopen(filename, "rb", use_include_path, context);
   if (same(f, false)) {
     Logger::Verbose("%s/%d: %s", __FUNCTION__, __LINE__,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
   Variant ret = f_fpassthru(f.toResource());
@@ -855,7 +856,7 @@ Variant f_readlink_internal(CStrRef path, bool warning_compliance) {
   int ret = readlink(File::TranslatePath(path).data(), buff, PATH_MAX-1);
   if (ret < 0) {
     Logger::Verbose("%s/%d: %s", __FUNCTION__, __LINE__,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     if (warning_compliance) {
       raise_warning("readlink(): No such file or directory %s",path.c_str());
     }
@@ -1051,7 +1052,7 @@ bool f_touch(CStrRef filename, int64_t mtime /* = 0 */, int64_t atime /* = 0 */)
     if (f == NULL) {
       Logger::Verbose("%s/%d: Unable to create file %s because %s",
                       __FUNCTION__, __LINE__, translated.data(),
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
       return false;
     }
     fclose(f);
@@ -1265,7 +1266,7 @@ Variant f_tempnam(CStrRef dir, CStrRef prefix) {
   int fd = mkstemp(buf);
   if (fd < 0) {
     Logger::Verbose("%s/%d: %s", __FUNCTION__, __LINE__,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
 
diff --git a/hphp/runtime/ext/ext_ipc.cpp b/hphp/runtime/ext/ext_ipc.cpp
index 49e9c3caa..160f87dd9 100644
--- a/hphp/runtime/ext/ext_ipc.cpp
+++ b/hphp/runtime/ext/ext_ipc.cpp
@@ -20,6 +20,7 @@
 #include "hphp/runtime/base/variable-unserializer.h"
 #include "hphp/util/lock.h"
 #include "hphp/util/alloc.h"
+#include "folly/String.h"
 
 #include <memory>
 
@@ -87,7 +88,7 @@ Variant f_msg_get_queue(int64_t key, int64_t perms /* = 0666 */) {
     id = msgget(key, IPC_CREAT | IPC_EXCL | perms);
     if (id < 0) {
       raise_warning("Failed to create message queue for key 0x%" PRIx64 ": %s",
-                      key, Util::safe_strerror(errno).c_str());
+                      key, folly::errnoStr(errno).c_str());
       return false;
     }
   }
@@ -200,7 +201,7 @@ bool f_msg_send(CResRef queue, int64_t msgtype, CVarRef message,
   if (result < 0) {
     int err = errno;
     raise_warning("Unable to send message: %s",
-                    Util::safe_strerror(err).c_str());
+                    folly::errnoStr(err).c_str());
     if (!errorcode.isNull()) {
       errorcode = err;
     }
@@ -241,7 +242,7 @@ bool f_msg_receive(CResRef queue, int64_t desiredmsgtype, VRefParam msgtype,
   if (result < 0) {
     int err = errno;
     raise_warning("Unable to receive message: %s",
-                    Util::safe_strerror(err).c_str());
+                    folly::errnoStr(err).c_str());
     if (!errorcode.isNull()) {
       errorcode = err;
     }
@@ -324,7 +325,7 @@ public:
       if (errno != EINTR) {
         raise_warning("failed to %s key 0x%x: %s",
                         acquire ? "acquire" : "release",
-                        key, Util::safe_strerror(errno).c_str());
+                        key, folly::errnoStr(errno).c_str());
         return false;
       }
     }
@@ -386,7 +387,7 @@ Variant f_sem_get(int64_t key, int64_t max_acquire /* = 1 */,
   int semid = semget(key, 3, perm|IPC_CREAT);
   if (semid == -1) {
     raise_warning("failed for key 0x%" PRIx64 ": %s", key,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
 
@@ -418,7 +419,7 @@ Variant f_sem_get(int64_t key, int64_t max_acquire /* = 1 */,
   while (semop(semid, sop, 3) == -1) {
     if (errno != EINTR) {
       raise_warning("failed acquiring SYSVSEM_SETVAL for key 0x%" PRIx64 ": %s",
-                      key, Util::safe_strerror(errno).c_str());
+                      key, folly::errnoStr(errno).c_str());
       break;
     }
   }
@@ -427,7 +428,7 @@ Variant f_sem_get(int64_t key, int64_t max_acquire /* = 1 */,
   int count = semctl(semid, SYSVSEM_USAGE, GETVAL, NULL);
   if (count == -1) {
     raise_warning("failed for key 0x%" PRIx64 ": %s", key,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
 
   /* If we are the only user, then take this opportunity to set the max. */
@@ -436,7 +437,7 @@ Variant f_sem_get(int64_t key, int64_t max_acquire /* = 1 */,
     semarg.val = max_acquire;
     if (semctl(semid, SYSVSEM_SEM, SETVAL, semarg) == -1) {
       raise_warning("failed for key 0x%" PRIx64 ": %s", key,
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
     }
   }
 
@@ -447,7 +448,7 @@ Variant f_sem_get(int64_t key, int64_t max_acquire /* = 1 */,
   while (semop(semid, sop, 1) == -1) {
     if (errno != EINTR) {
       raise_warning("failed releasing SYSVSEM_SETVAL for key 0x%" PRIx64 ": %s",
-                      key, Util::safe_strerror(errno).c_str());
+                      key, folly::errnoStr(errno).c_str());
       break;
     }
   }
@@ -479,7 +480,7 @@ bool f_sem_remove(CResRef sem_identifier) {
   if (semctl(sem_ptr->semid, 0, IPC_RMID, un) < 0) {
     raise_warning("failed for SysV sempphore %d: %s",
                     sem_identifier->o_getId(),
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
 
@@ -620,14 +621,14 @@ Variant f_shm_attach(int64_t shm_key, int64_t shm_size /* = 10000 */,
     if ((shm_id = shmget(shm_key, shm_size, shm_flag | IPC_CREAT | IPC_EXCL))
         < 0) {
       raise_warning("failed for key 0x%" PRIx64 ": %s", shm_key,
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
       return false;
     }
   }
 
   if ((shm_ptr = (char*)shmat(shm_id, NULL, 0)) == (char *)-1) {
     raise_warning("failed for key 0x%" PRIx64 ": %s", shm_key,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
 
@@ -676,7 +677,7 @@ bool f_shm_remove(int64_t shm_identifier) {
 
   if (shmctl(shm_list_ptr->id, IPC_RMID,NULL) < 0) {
     raise_warning("failed for key 0x%x, id %" PRId64 ": %s", shm_list_ptr->key,
-                    shm_identifier, Util::safe_strerror(errno).c_str());
+                    shm_identifier, folly::errnoStr(errno).c_str());
     return false;
   }
   return true;
diff --git a/hphp/runtime/ext/ext_ldap.cpp b/hphp/runtime/ext/ext_ldap.cpp
index 8dcb06a55..c557f5db5 100644
--- a/hphp/runtime/ext/ext_ldap.cpp
+++ b/hphp/runtime/ext/ext_ldap.cpp
@@ -19,6 +19,7 @@
 #include "hphp/runtime/ext/ext_function.h"
 #include "hphp/runtime/base/builtin-functions.h"
 #include "hphp/util/thread_local.h"
+#include "folly/String.h"
 #include <lber.h>
 
 #define LDAP_DEPRECATED 1
@@ -556,7 +557,7 @@ Variant f_ldap_connect(CStrRef hostname /* = null_string */,
     return ret;
   }
   raise_warning("Unable to initialize LDAP: %s",
-                Util::safe_strerror(errno).c_str());
+                folly::errnoStr(errno).c_str());
   return false;
 }
 
diff --git a/hphp/runtime/ext/ext_mysql.cpp b/hphp/runtime/ext/ext_mysql.cpp
index 1cd6f75db..31d45ea92 100644
--- a/hphp/runtime/ext/ext_mysql.cpp
+++ b/hphp/runtime/ext/ext_mysql.cpp
@@ -28,6 +28,7 @@
 #include "hphp/runtime/base/extended-logger.h"
 #include "hphp/util/timer.h"
 #include "hphp/util/db_mysql.h"
+#include "folly/String.h"
 #include "netinet/in.h"
 #include <netdb.h>
 
@@ -1504,7 +1505,7 @@ Variant f_mysql_async_wait_actionable(CVarRef items, double timeout) {
   int res = poll(fds, nfds, timeout_millis);
   if (res == -1) {
     raise_warning("unable to poll [%d]: %s", errno,
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
     return Array::Create();
   }
 
diff --git a/hphp/runtime/ext/ext_posix.cpp b/hphp/runtime/ext/ext_posix.cpp
index 881db2cac..229dd8b8e 100644
--- a/hphp/runtime/ext/ext_posix.cpp
+++ b/hphp/runtime/ext/ext_posix.cpp
@@ -17,6 +17,7 @@
 
 #include "hphp/runtime/ext/ext_posix.h"
 #include "hphp/runtime/base/file.h"
+#include "folly/String.h"
 #include <sys/times.h>
 #include <sys/utsname.h>
 #include <sys/types.h>
@@ -367,7 +368,7 @@ bool f_posix_setuid(int uid) {
 }
 
 String f_posix_strerror(int errnum) {
-  return String(Util::safe_strerror(errnum));
+  return String(folly::errnoStr(errnum).toStdString());
 }
 
 const StaticString
diff --git a/hphp/runtime/ext/ext_process.cpp b/hphp/runtime/ext/ext_process.cpp
index ed142cc78..37906f87f 100644
--- a/hphp/runtime/ext/ext_process.cpp
+++ b/hphp/runtime/ext/ext_process.cpp
@@ -21,6 +21,7 @@
 #include "hphp/runtime/base/string-buffer.h"
 #include "hphp/runtime/base/zend-string.h"
 #include "hphp/runtime/base/thread-init-fini.h"
+#include "folly/String.h"
 #include <unistd.h>
 #include <fcntl.h>
 #include <signal.h>
@@ -142,7 +143,7 @@ void f_pcntl_exec(CStrRef path, CArrRef args /* = null_array */,
   char **envp = build_envp(envs, senvs);
   if (execve(path.c_str(), argv, envp) == -1) {
     raise_warning("Error has occured: (errno %d) %s",
-                    errno, Util::safe_strerror(errno).c_str());
+                    errno, folly::errnoStr(errno).c_str());
   }
 
   free(envp);
@@ -598,7 +599,7 @@ public:
     childend = dup(file->fd());
     if (childend < 0) {
       raise_warning("unable to dup File-Handle for descriptor %d - %s",
-                      index, Util::safe_strerror(errno).c_str());
+                      index, folly::errnoStr(errno).c_str());
       return false;
     }
     return true;
@@ -609,7 +610,7 @@ public:
     int newpipe[2];
     if (0 != pipe(newpipe)) {
       raise_warning("unable to create pipe %s",
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
       return false;
     }
 
@@ -741,7 +742,7 @@ static Variant post_proc_open(CStrRef cmd, Variant &pipes,
     for (int i = 0; i < (int)items.size(); i++) {
       items[i].cleanup();
     }
-    raise_warning("fork failed - %s", Util::safe_strerror(errno).c_str());
+    raise_warning("fork failed - %s", folly::errnoStr(errno).c_str());
     return false;
   }
 
diff --git a/hphp/runtime/ext/ext_session.cpp b/hphp/runtime/ext/ext_session.cpp
index 9199ea51c..147b2f6f0 100644
--- a/hphp/runtime/ext/ext_session.cpp
+++ b/hphp/runtime/ext/ext_session.cpp
@@ -32,6 +32,7 @@
 #include "hphp/util/lock.h"
 #include "hphp/util/logger.h"
 #include "hphp/util/compatibility.h"
+#include "folly/String.h"
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -630,7 +631,8 @@ public:
 
     if (n != (int)m_st_size) {
       if (n == -1) {
-        raise_warning("read failed: %s (%d)", strerror(errno), errno);
+        raise_warning("read failed: %s (%d)", folly::errnoStr(errno).c_str(),
+                      errno);
       } else {
         raise_warning("read returned less bytes than requested");
       }
@@ -659,7 +661,8 @@ public:
      */
     if (value.size() < (int)m_st_size) {
       if (ftruncate(m_fd, 0) < 0) {
-        raise_warning("truncate failed: %s (%d)", strerror(errno), errno);
+        raise_warning("truncate failed: %s (%d)",
+                      folly::errnoStr(errno).c_str(), errno);
         return false;
       }
     }
@@ -673,7 +676,8 @@ public:
 
     if (n != value.size()) {
       if (n == -1) {
-        raise_warning("write failed: %s (%d)", strerror(errno), errno);
+        raise_warning("write failed: %s (%d)",
+                      folly::errnoStr(errno).c_str(), errno);
       } else {
         raise_warning("write wrote less bytes than requested");
       }
@@ -816,12 +820,12 @@ private:
 # endif
         if (fcntl(m_fd, F_SETFD, FD_CLOEXEC)) {
           raise_warning("fcntl(%d, F_SETFD, FD_CLOEXEC) failed: %s (%d)",
-                        m_fd, strerror(errno), errno);
+                        m_fd, folly::errnoStr(errno).c_str(), errno);
         }
 #endif
       } else {
         raise_warning("open(%s, O_RDWR) failed: %s (%d)", buf,
-                      strerror(errno), errno);
+                      folly::errnoStr(errno).c_str(), errno);
       }
     }
   }
@@ -830,7 +834,7 @@ private:
     DIR *dir = opendir(dirname);
     if (!dir) {
       raise_notice("ps_files_cleanup_dir: opendir(%s) failed: %s (%d)",
-                   dirname, strerror(errno), errno);
+                   dirname, folly::errnoStr(errno).c_str(), errno);
       return 0;
     }
 
diff --git a/hphp/runtime/ext/ext_socket.cpp b/hphp/runtime/ext/ext_socket.cpp
index b5b656fd0..e950da1f1 100644
--- a/hphp/runtime/ext/ext_socket.cpp
+++ b/hphp/runtime/ext/ext_socket.cpp
@@ -19,6 +19,7 @@
 #include "hphp/runtime/base/socket.h"
 #include "hphp/runtime/base/ssl-socket.h"
 #include "hphp/runtime/server/server_stats.h"
+#include "folly/String.h"
 
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -306,7 +307,7 @@ static bool create_new_socket(const char *&name, int port, Variant &errnum,
   if (!sock->valid()) {
     SOCKET_ERROR(sock, "unable to create socket", errno);
     errnum = sock->getError();
-    errstr = String(Util::safe_strerror(sock->getError()));
+    errstr = String(folly::errnoStr(sock->getError()).toStdString());
     return false;
   }
   return true;
@@ -645,7 +646,7 @@ Variant f_socket_select(VRefParam read, VRefParam write, VRefParam except,
   int retval = poll(fds, count, timeout_ms);
   if (retval == -1) {
     raise_warning("unable to select [%d]: %s", errno,
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
     free(fds);
     return false;
   }
@@ -962,7 +963,7 @@ void f_socket_close(CResRef socket) {
 }
 
 String f_socket_strerror(int errnum) {
-  return String(Util::safe_strerror(errnum));
+  return String(folly::errnoStr(errnum).toStdString());
 }
 
 int64_t f_socket_last_error(CResRef socket /* = null_object */) {
@@ -1054,7 +1055,7 @@ static Variant sockopen_impl(CStrRef hostname, int port, Variant &errnum,
             msg += boost::lexical_cast<std::string>(port);
             SOCKET_ERROR(sock, msg.c_str(), valopt);
             errnum = sock->getError();
-            errstr = String(Util::safe_strerror(sock->getError()));
+            errstr = String(folly::errnoStr(sock->getError()).toStdString());
             return false;
           } else {
             retval = 0; // success
@@ -1068,7 +1069,7 @@ static Variant sockopen_impl(CStrRef hostname, int port, Variant &errnum,
           msg += boost::lexical_cast<std::string>(port);
           SOCKET_ERROR(sock, msg.c_str(), ETIMEDOUT);
           errnum = sock->getError();
-          errstr = String(Util::safe_strerror(sock->getError()));
+          errstr = String(folly::errnoStr(sock->getError()).toStdString());
           return false;
         }
       }
@@ -1081,7 +1082,7 @@ static Variant sockopen_impl(CStrRef hostname, int port, Variant &errnum,
 
   if (retval != 0) {
     errnum = sock->getError();
-    errstr = String(Util::safe_strerror(sock->getError()));
+    errstr = String(folly::errnoStr(sock->getError()).toStdString());
     return false;
   }
 
diff --git a/hphp/runtime/ext/ext_zlib.cpp b/hphp/runtime/ext/ext_zlib.cpp
index 43ca0cfce..d447f5f78 100644
--- a/hphp/runtime/ext/ext_zlib.cpp
+++ b/hphp/runtime/ext/ext_zlib.cpp
@@ -24,6 +24,7 @@
 #include "hphp/runtime/base/file-stream-wrapper.h"
 #include "hphp/util/compression.h"
 #include "hphp/util/logger.h"
+#include "folly/String.h"
 #ifdef HAVE_SNAPPY
 #include <snappy.h>
 #endif
@@ -321,7 +322,7 @@ Resource f_gzopen(CStrRef filename, CStrRef mode,
   Resource handle(file);
   bool ret = file->open(File::TranslatePath(filename), mode);
   if (!ret) {
-    raise_warning("%s",Util::safe_strerror(errno).c_str());
+    raise_warning("%s",folly::errnoStr(errno).c_str());
     return NULL;
   }
   return handle;
diff --git a/hphp/runtime/server/libevent_server_with_fd.cpp b/hphp/runtime/server/libevent_server_with_fd.cpp
index 576aa1438..efdc19fd8 100644
--- a/hphp/runtime/server/libevent_server_with_fd.cpp
+++ b/hphp/runtime/server/libevent_server_with_fd.cpp
@@ -16,6 +16,7 @@
 
 #include "hphp/runtime/server/libevent_server_with_fd.h"
 #include "hphp/util/logger.h"
+#include "folly/String.h"
 
 /*
  * LibEventServer that supports using existing/inherited accept sockets.
@@ -40,14 +41,14 @@ int LibEventServerWithFd::getAcceptSocket() {
   int ret = listen(m_accept_sock, RuntimeOption::ServerBacklog);
   if (ret != 0) {
     Logger::Error("inheritfd: listen() failed: %s",
-        Util::safe_strerror(errno).c_str());
+        folly::errnoStr(errno).c_str());
     return -1;
   }
 
   ret = evhttp_accept_socket(m_server, m_accept_sock);
   if (ret < 0) {
     Logger::Error("evhttp_accept_socket: %s",
-        Util::safe_strerror(errno).c_str());
+        folly::errnoStr(errno).c_str());
     int errno_save = errno;
     close(m_accept_sock);
     m_accept_sock = -1;
@@ -69,14 +70,14 @@ int LibEventServerWithFd::getAcceptSocketSSL() {
   int ret = listen(m_accept_sock_ssl, RuntimeOption::ServerBacklog);
   if (ret != 0) {
     Logger::Error("inheritfd: listen() failed for ssl: %s",
-        Util::safe_strerror(errno).c_str());
+        folly::errnoStr(errno).c_str());
     return -1;
   }
 
   ret = evhttp_accept_socket(m_server_ssl, m_accept_sock_ssl);
   if (ret < 0) {
     Logger::Error("evhttp_accept_socket: (ssl) %s",
-        Util::safe_strerror(errno).c_str());
+        folly::errnoStr(errno).c_str());
     int errno_save = errno;
     close(m_accept_sock_ssl);
     m_accept_sock_ssl = -1;
diff --git a/hphp/runtime/server/libevent_server_with_takeover.cpp b/hphp/runtime/server/libevent_server_with_takeover.cpp
index f7f139771..96af450f6 100644
--- a/hphp/runtime/server/libevent_server_with_takeover.cpp
+++ b/hphp/runtime/server/libevent_server_with_takeover.cpp
@@ -17,6 +17,7 @@
 #include "hphp/runtime/server/libevent_server_with_takeover.h"
 #include "hphp/util/logger.h"
 #include "hphp/runtime/base/string-util.h"
+#include "folly/String.h"
 #include <afdt.h>
 
 /*
@@ -63,7 +64,7 @@ static void fd_transfer_error_hander(
       afdt_phase_str(err->phase),
       afdt_operation_str(err->operation),
       err->message,
-      Util::safe_strerror(errno).c_str());
+      folly::errnoStr(errno).c_str());
 }
 
 static int fd_transfer_request_handler(
@@ -168,7 +169,7 @@ void LibEventServerWithTakeover::setupFdServer() {
   ret = unlink(m_transfer_fname.c_str());
   if (ret < 0 && errno != ENOENT) {
     Logger::Error("Unalbe to unlink '%s': %s",
-                  m_transfer_fname.c_str(), Util::safe_strerror(errno).c_str());
+                  m_transfer_fname.c_str(), folly::errnoStr(errno).c_str());
     return;
   }
 
@@ -248,7 +249,7 @@ int LibEventServerWithTakeover::getAcceptSocket() {
   ret = evhttp_accept_socket(m_server, m_accept_sock);
   if (ret < 0) {
     Logger::Error("evhttp_accept_socket: %s",
-        Util::safe_strerror(errno).c_str());
+        folly::errnoStr(errno).c_str());
     int errno_save = errno;
     close(m_accept_sock);
     m_accept_sock = -1;
diff --git a/hphp/runtime/server/transport.cpp b/hphp/runtime/server/transport.cpp
index b9dc5dda5..0d63b958d 100644
--- a/hphp/runtime/server/transport.cpp
+++ b/hphp/runtime/server/transport.cpp
@@ -32,6 +32,7 @@
 #include "hphp/util/compatibility.h"
 #include "hphp/util/timer.h"
 #include "hphp/runtime/base/hardware-counter.h"
+#include "folly/String.h"
 
 namespace HPHP {
 ///////////////////////////////////////////////////////////////////////////////
@@ -837,7 +838,7 @@ bool Transport::moveUploadedFileHelper(CStrRef filename, CStrRef destination) {
   if (Util::rename(filename.c_str(), dest.c_str()) < 0) {
     Logger::Error("Unable to move uploaded file %s to %s: %s.",
                   filename.c_str(), dest.c_str(),
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
     return false;
   }
   Logger::Verbose("Successfully moved uploaded file %s to %s.",
diff --git a/hphp/runtime/vm/as.cpp b/hphp/runtime/vm/as.cpp
index 0659d8225..9d5f7f331 100644
--- a/hphp/runtime/vm/as.cpp
+++ b/hphp/runtime/vm/as.cpp
@@ -89,6 +89,8 @@
 #include <boost/noncopyable.hpp>
 #include <boost/bind.hpp>
 
+#include "folly/String.h"
+
 #include "hphp/runtime/vm/unit.h"
 #include "hphp/runtime/vm/hhbc.h"
 #include "hphp/runtime/vm/preclass-emit.h"
@@ -319,7 +321,7 @@ private:
   void io_error_if_bad() {
     if (m_in.bad()) {
       error("I/O error reading stream: " +
-        std::string(strerror(errno)));
+        folly::errnoStr(errno).toStdString());
     }
   }
 
diff --git a/hphp/runtime/vm/backup-gc.cpp b/hphp/runtime/vm/backup-gc.cpp
index aac07b8b1..ace7f24ff 100644
--- a/hphp/runtime/vm/backup-gc.cpp
+++ b/hphp/runtime/vm/backup-gc.cpp
@@ -22,6 +22,8 @@
 #include <boost/noncopyable.hpp>
 #include <map>
 
+#include "folly/String.h"
+
 #include "hphp/util/assertions.h"
 #include "hphp/util/timer.h"
 #include "hphp/util/trace.h"
@@ -571,7 +573,7 @@ void gc_detect_cycles(const std::string& filename) {
   std::ofstream out(filename.c_str());
   if (!out.is_open()) {
     raise_error("couldn't open output file for gc_detect_cycles, %s",
-                strerror(errno));
+                folly::errnoStr(errno).c_str());
     return;
   }
 
diff --git a/hphp/runtime/vm/bytecode.cpp b/hphp/runtime/vm/bytecode.cpp
index 0ac18b258..ed58cbd6d 100644
--- a/hphp/runtime/vm/bytecode.cpp
+++ b/hphp/runtime/vm/bytecode.cpp
@@ -531,7 +531,8 @@ class StackElms {
       size_t algnSz = RuntimeOption::EvalVMStackElms * sizeof(TypedValue);
       if (posix_memalign((void**)&m_elms, algnSz, algnSz) != 0) {
         throw std::runtime_error(
-          std::string("VM stack initialization failed: ") + strerror(errno));
+          std::string("VM stack initialization failed: ") +
+                      folly::errnoStr(errno).c_str());
       }
     }
     return m_elms;
diff --git a/hphp/runtime/vm/jit/translator-x64.cpp b/hphp/runtime/vm/jit/translator-x64.cpp
index 0e3bc6508..86415d899 100644
--- a/hphp/runtime/vm/jit/translator-x64.cpp
+++ b/hphp/runtime/vm/jit/translator-x64.cpp
@@ -51,6 +51,7 @@
 #include <boost/scoped_ptr.hpp>
 
 #include "folly/Format.h"
+#include "folly/String.h"
 
 #include "hphp/util/asm-x64.h"
 #include "hphp/util/bitops.h"
@@ -3859,7 +3860,7 @@ TranslatorX64::TranslatorX64()
     if (sigaction(SIGSEGV, &sa, &old_sa) != 0) {
       throw std::runtime_error(
         std::string("Failed to install SIGSEGV handler: ") +
-          strerror(errno));
+          folly::errnoStr(errno).c_str());
     }
     m_segvChain = old_sa.sa_flags & SA_SIGINFO ?
       old_sa.sa_sigaction : (sigaction_t)old_sa.sa_handler;
diff --git a/hphp/runtime/vm/type-profile.cpp b/hphp/runtime/vm/type-profile.cpp
index 24415f7c7..27ad049e7 100644
--- a/hphp/runtime/vm/type-profile.cpp
+++ b/hphp/runtime/vm/type-profile.cpp
@@ -19,6 +19,8 @@
 #include "hphp/runtime/vm/jit/translator.h"
 #include "hphp/util/trace.h"
 
+#include "folly/String.h"
+
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -106,7 +108,7 @@ profileInitMmap() {
   int fd = open(path.c_str(), O_RDWR | O_CREAT, 0600);
   if (fd < 0) {
     TRACE(0, "profileInit: open %s failed: %s\n", path.c_str(),
-          strerror(errno));
+          folly::errnoStr(errno).c_str());
     perror("open");
     return nullptr;
   }
@@ -116,7 +118,7 @@ profileInitMmap() {
   if (retval < 0) {
     perror("truncate");
     TRACE(0, "profileInit: truncate %s failed: %s\n", path.c_str(),
-          strerror(errno));
+          folly::errnoStr(errno).c_str());
     return nullptr;
   }
 
@@ -127,7 +129,7 @@ profileInitMmap() {
   if (mmapRet == MAP_FAILED) {
     perror("mmap");
     TRACE(0, "profileInit: mmap %s failed: %s\n", path.c_str(),
-          strerror(errno));
+          folly::errnoStr(errno).c_str());
     return nullptr;
   }
   return (ValueProfileLine*)mmapRet;
diff --git a/hphp/util/asm-x64.cpp b/hphp/util/asm-x64.cpp
index d69f29b9c..f397212eb 100644
--- a/hphp/util/asm-x64.cpp
+++ b/hphp/util/asm-x64.cpp
@@ -25,6 +25,8 @@
 #include <sys/mman.h>
 #include <sys/types.h>
 
+#include "folly/String.h"
+
 #include "hphp/util/assertions.h"
 #include "hphp/util/maphuge.h"
 #include "hphp/runtime/base/runtime-option.h"
@@ -45,7 +47,7 @@ Address allocSlab(size_t size) {
     mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
   if (result == MAP_FAILED) {
     panic("%s:%d: (%s) map of %zu bytes failed (%s)\n",
-          __FILE__, __LINE__, __func__, size, strerror(errno));
+          __FILE__, __LINE__, __func__, size, folly::errnoStr(errno).c_str());
   }
   return result;
 }
@@ -77,7 +79,7 @@ void DataBlock::makeExecable() {
   if (mprotect(base, size, PROT_READ | PROT_WRITE | PROT_EXEC)) {
     panic("%s:%d (%s): mprotect @%p %zu bytes failed (%s)\n",
           __FILE__, __LINE__, __func__,
-          base, (long)size, strerror(errno));
+          base, (long)size, folly::errnoStr(errno).c_str());
   }
 }
 
diff --git a/hphp/util/capability.cpp b/hphp/util/capability.cpp
index 557754e3b..2986068c7 100644
--- a/hphp/util/capability.cpp
+++ b/hphp/util/capability.cpp
@@ -18,6 +18,7 @@
 
 #include "hphp/util/capability.h"
 #include "hphp/util/logger.h"
+#include "folly/String.h"
 #include "linux/types.h"
 #include <sys/capability.h>
 #include <sys/prctl.h>
@@ -96,17 +97,20 @@ bool Capability::ChangeUnixUser(uid_t uid) {
     struct passwd *pw;
 
     if ((pw = getpwuid(uid)) == nullptr) {
-      Logger::Error("unable to getpwuid(%d): %s", uid, strerror(errno));
+      Logger::Error("unable to getpwuid(%d): %s", uid,
+                    folly::errnoStr(errno).c_str());
       return false;
     }
 
     if (pw->pw_gid == 0 || setgid(pw->pw_gid) < 0) {
-      Logger::Error("unable to drop gid privs: %s", strerror(errno));
+      Logger::Error("unable to drop gid privs: %s",
+                    folly::errnoStr(errno).c_str());
       return false;
     }
 
     if (uid == 0 || setuid(uid) < 0) {
-      Logger::Error("unable to drop uid privs: %s", strerror(errno));
+      Logger::Error("unable to drop uid privs: %s",
+                    folly::errnoStr(errno).c_str());
       return false;
     }
 
@@ -131,7 +135,8 @@ bool Capability::ChangeUnixUser(const std::string &username) {
 
 bool Capability::SetDumpable() {
   if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0)) {
-    Logger::Error("Unable to make process dumpable: %s", strerror(errno));
+    Logger::Error("Unable to make process dumpable: %s",
+                  folly::errnoStr(errno).c_str());
   }
 
   return true;
diff --git a/hphp/util/file_cache.cpp b/hphp/util/file_cache.cpp
index 5c8339ce4..6971fabf3 100644
--- a/hphp/util/file_cache.cpp
+++ b/hphp/util/file_cache.cpp
@@ -19,6 +19,7 @@
 #include "hphp/util/compression.h"
 #include "util.h"
 #include "hphp/util/logger.h"
+#include "folly/String.h"
 #include <sys/mman.h>
 
 namespace HPHP {
@@ -125,7 +126,7 @@ void FileCache::write(const char *name, const char *fullpath) {
   struct stat sb;
   if (stat(fullpath, &sb) != 0) {
     throw Exception("Unable to stat %s: %s", fullpath,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
   int len = sb.st_size;
   Buffer &buffer = m_files[name];
@@ -138,7 +139,7 @@ void FileCache::write(const char *name, const char *fullpath) {
     FILE *f = fopen(fullpath, "r");
     if (f == nullptr) {
       throw Exception("Unable to open %s: %s", fullpath,
-                      Util::safe_strerror(errno).c_str());
+                      folly::errnoStr(errno).c_str());
     }
 
     char *buf = buffer.data = (char *)malloc(len);
@@ -171,7 +172,7 @@ void FileCache::save(const char *filename) {
   FILE *f = fopen(filename, "w");
   if (f == nullptr) {
     throw Exception("Unable to open %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
 
   // write an invalid length followed by a version number
@@ -215,7 +216,7 @@ short FileCache::getVersion(const char *filename) {
   FILE *f = fopen(filename, "r");
   if (f == nullptr) {
     throw Exception("Unable to open %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
 
   short tag = -1;
@@ -233,7 +234,7 @@ void FileCache::load(const char *filename, bool onDemandUncompress,
   FILE *f = fopen(filename, "r");
   if (f == nullptr) {
     throw Exception("Unable to open %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
 
   if (version > 0) {
@@ -313,7 +314,7 @@ void FileCache::load(const char *filename, bool onDemandUncompress,
 void FileCache::adviseOutMemory() {
   if (posix_madvise(m_addr, m_size, POSIX_MADV_DONTNEED)) {
     Logger::Error("posix_madvise failed: %s",
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
   }
 }
 
@@ -324,19 +325,19 @@ void FileCache::loadMmap(const char *filename, short version) {
   struct stat sbuf;
   if (stat(filename, &sbuf) == -1) {
     throw Exception("Unable to stat %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
   m_fd = open(filename, O_RDONLY);
   if (m_fd == -1) {
     throw Exception("Unable to open %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
 
   m_addr = mmap(nullptr, sbuf.st_size, PROT_READ, MAP_PRIVATE, m_fd, 0);
   if (m_addr == (void *)-1) {
     close(m_fd);
     throw Exception("Unable to mmap %s: %s", filename,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
   }
   m_size = sbuf.st_size;
   char *p = (char *)m_addr;
diff --git a/hphp/util/light_process.cpp b/hphp/util/light_process.cpp
index 2a5d18758..0d32b608e 100644
--- a/hphp/util/light_process.cpp
+++ b/hphp/util/light_process.cpp
@@ -18,6 +18,7 @@
 #include "hphp/util/process.h"
 #include "util.h"
 #include "hphp/util/logger.h"
+#include "folly/String.h"
 
 #include <afdt.h>
 #include <string>
@@ -124,7 +125,7 @@ static void do_popen(FILE *fin, FILE *fout, int afdt_fd) {
 
   if (f == nullptr) {
     Logger::Error("Light process failed popen: %d (%s).", errno,
-                  strerror(errno));
+                  folly::errnoStr(errno).c_str());
     fprintf(fout, "error\n");
     fflush(fout);
   } else {
@@ -367,7 +368,7 @@ bool LightProcess::initShadow(const std::string &prefix, int id,
   CPipe p1, p2;
   if (!p1.open() || !p2.open()) {
     Logger::Warning("Unable to create pipe: %d %s", errno,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   }
 
@@ -402,7 +403,7 @@ bool LightProcess::initShadow(const std::string &prefix, int id,
   } else if (child < 0) {
     // failed
     Logger::Warning("Unable to fork lightly: %d %s", errno,
-                    Util::safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     return false;
   } else {
     // parent
diff --git a/hphp/util/parser/xhpast2/xhpast2.cpp b/hphp/util/parser/xhpast2/xhpast2.cpp
index e7cffb5f0..616b7428f 100644
--- a/hphp/util/parser/xhpast2/xhpast2.cpp
+++ b/hphp/util/parser/xhpast2/xhpast2.cpp
@@ -18,6 +18,8 @@
 #include <cstdlib>
 #include <string.h>
 
+#include "folly/String.h"
+
 #include "hphp/util/parser/xhpast2/parser.h"
 
 namespace HPHP { namespace HPHP_PARSER_NS {
@@ -77,7 +79,7 @@ int main(int argc, char** argv) try {
   std::ifstream in(argv[1]);
   if (!in.is_open()) {
     std::cerr << argv[0] << ": couldn't open file: "
-              << strerror(errno) << '\n';
+              << folly::errnoStr(errno).toStdString() << '\n';
   }
 
   std::cout << "1..1\n";
diff --git a/hphp/util/process.cpp b/hphp/util/process.cpp
index ee36b59cf..080529821 100644
--- a/hphp/util/process.cpp
+++ b/hphp/util/process.cpp
@@ -20,6 +20,7 @@
 #include "hphp/util/logger.h"
 #include "hphp/util/async_func.h"
 #include "hphp/util/text_color.h"
+#include "folly/String.h"
 
 #include <pwd.h>
 
@@ -186,7 +187,7 @@ int Process::Exec(const std::string &cmd, const std::string &outf,
   int pid = fork();
   if (pid < 0) {
     Logger::Error("Unable to fork: %d %s", errno,
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
     return 0;
   }
   if (pid == 0) {
@@ -221,7 +222,7 @@ int Process::Exec(const char *path, const char *argv[], int *fdin, int *fdout,
   int pid = fork();
   if (pid < 0) {
     Logger::Error("Unable to fork: %d %s", errno,
-                  Util::safe_strerror(errno).c_str());
+                  folly::errnoStr(errno).c_str());
     return 0;
   }
   if (pid == 0) {
diff --git a/hphp/util/util.cpp b/hphp/util/util.cpp
index 82e7be6dc..19bf6fe0f 100644
--- a/hphp/util/util.cpp
+++ b/hphp/util/util.cpp
@@ -20,6 +20,7 @@
 #include "hphp/util/logger.h"
 #include "hphp/util/exception.h"
 #include "hphp/util/network.h"
+#include "folly/String.h"
 
 #include <sys/types.h>
 #include <dirent.h>
@@ -266,11 +267,11 @@ int Util::copy(const char *srcfile, const char *dstfile) {
     if (rbytes == 0) break;
     if (rbytes == -1) {
       err = true;
-      Logger::Error("read failed: %s", safe_strerror(errno).c_str());
+      Logger::Error("read failed: %s", folly::errnoStr(errno).c_str());
     } else if ((wbytes = write(dstFd, buf, rbytes)) != rbytes) {
       err = true;
       Logger::Error("write failed: %zd, %s", wbytes,
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     }
     if (err) {
       close(srcFd);
@@ -342,27 +343,27 @@ int Util::directCopy(const char *srcfile, const char *dstfile) {
 
     if (rbytes == -1) {
       err = true;
-      Logger::Error("read failed: %s", safe_strerror(errno).c_str());
+      Logger::Error("read failed: %s", folly::errnoStr(errno).c_str());
     } else if (force_sync(srcFd) == -1) {
       err = true;
       Logger::Error("read sync failed: %s",
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     } else if (drop_cache(srcFd) == -1) {
       err = true;
       Logger::Error("read cache drop failed: %s",
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     } else if ((wbytes = write(dstFd, buf, rbytes)) != rbytes) {
       err = true;
       Logger::Error("write failed: %zd, %s", wbytes,
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     } else if (force_sync(dstFd) == -1) {
       err = true;
       Logger::Error("write sync failed: %s",
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     } else if (drop_cache(dstFd) == -1) {
       err = true;
       Logger::Error("write cache drop failed: %s",
-                    safe_strerror(errno).c_str());
+                    folly::errnoStr(errno).c_str());
     }
     if (err) {
       close(srcFd);
@@ -398,23 +399,14 @@ int Util::directRename(const char *oldname, const char *newname) {
 int Util::ssystem(const char* command) {
   int ret = system(command);
   if (ret == -1) {
-    Logger::Error("system(\"%s\"): %s", command, safe_strerror(errno).c_str());
+    Logger::Error("system(\"%s\"): %s", command,
+                  folly::errnoStr(errno).c_str());
   } else if (ret != 0) {
     Logger::Error("command failed: \"%s\"", command);
   }
   return ret;
 }
 
-std::string Util::safe_strerror(int errnum) {
-  char buf[1024];
-#ifdef __GLIBC__
-  return strerror_r(errnum, buf, sizeof(buf));
-#else
-  strerror_r(errnum, buf, sizeof(buf));
-  return buf;
-#endif
-}
-
 size_t Util::dirname_helper(char *path, int len) {
   if (len == 0) {
     /* Illegal use of this function */
diff --git a/hphp/util/util.h b/hphp/util/util.h
index 7945207dc..a88f31f0c 100644
--- a/hphp/util/util.h
+++ b/hphp/util/util.h
@@ -195,11 +195,6 @@ const char *canonicalize(const char *path, size_t len,
  */
 std::string normalizeDir(const std::string &dirname);
 
-/**
- * Thread-safe strerror().
- */
-std::string safe_strerror(int errnum);
-
 /**
  * Thread-safe dirname().
  */