From a9c3630d1bb2760546470845c34fcc1dc04bb561 Mon Sep 17 00:00:00 2001
From: dominicpoeschko <45942148+dominicpoeschko@users.noreply.github.com>
Date: Fri, 7 Feb 2020 17:59:11 +0100
Subject: [PATCH 1/2] Properly handling SPDLOG_PREVENT_CHILD_FD

Using the SPDLOG_PREVENT_CHILD_FD option there where still a race when
a other thread was using fork and exec in between the call to fopen and fcntl.

Using open and O_CLOEXEC when possible prevents this race.

I have no idea if this problem  exists on Windows.
---
 include/spdlog/details/os-inl.h | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/spdlog/details/os-inl.h b/include/spdlog/details/os-inl.h
index 8473eb09..b306e318 100644
--- a/include/spdlog/details/os-inl.h
+++ b/include/spdlog/details/os-inl.h
@@ -153,10 +153,26 @@ SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename
     *fp = ::_fsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
 #endif
 #else // unix
+#if defined(SPDLOG_PREVENT_CHILD_FD) && (defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
+    //  prevent child processes from inheriting log file descriptors direcly on open
+    //  so there is no race with a possible fork and exec
+    const int mode_flag = mode == SPDLOG_FILENAME_T("ab") ? O_APPEND : O_TRUNC;
+    const int fd = ::open((filename.c_str()), O_CREAT | O_WRONLY | O_CLOEXEC | mode_flag, mode_t(0644));
+    if(fd == -1)
+    {
+        return false;
+    }
+    *fp = ::fdopen(fd, mode.c_str());
+    if (*fp == nullptr)
+    {
+        ::close(fd);
+    }
+#else
     *fp = ::fopen((filename.c_str()), mode.c_str());
 #endif
+#endif
 
-#ifdef SPDLOG_PREVENT_CHILD_FD
+#if defined(SPDLOG_PREVENT_CHILD_FD) && !(defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
     //  prevent child processes from inheriting log file descriptors
     if (*fp != nullptr)
     {

From 033fe9f133092dd8d13cdd52a882a7c291a4a48d Mon Sep 17 00:00:00 2001
From: dominic <mail@dominicp.de>
Date: Sat, 8 Feb 2020 12:15:05 +0100
Subject: [PATCH 2/2] Properly handling SPDLOG_PREVENT_CHILD_FD

Removed check for posix version so that missing O_CLOEXEC leads to
compiler error.

Removed extra function since it hat no real purpose anymore.

Error behavior between Windows and Unix now equivalent.
---
 include/spdlog/details/os-inl.h | 39 ++++++++++-----------------------
 include/spdlog/details/os.h     |  4 ----
 2 files changed, 12 insertions(+), 31 deletions(-)

diff --git a/include/spdlog/details/os-inl.h b/include/spdlog/details/os-inl.h
index b306e318..ccc53ff2 100644
--- a/include/spdlog/details/os-inl.h
+++ b/include/spdlog/details/os-inl.h
@@ -126,23 +126,6 @@ SPDLOG_INLINE std::tm gmtime() SPDLOG_NOEXCEPT
     return gmtime(now_t);
 }
 
-#ifdef SPDLOG_PREVENT_CHILD_FD
-SPDLOG_INLINE void prevent_child_fd(FILE *f)
-{
-#ifdef _WIN32
-    auto file_handle = reinterpret_cast<HANDLE>(_get_osfhandle(::_fileno(f)));
-    if (!::SetHandleInformation(file_handle, HANDLE_FLAG_INHERIT, 0))
-        SPDLOG_THROW(spdlog_ex("SetHandleInformation failed", errno));
-#else
-    auto fd = ::fileno(f);
-    if (::fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
-    {
-        SPDLOG_THROW(spdlog_ex("fcntl with FD_CLOEXEC failed", errno));
-    }
-#endif
-}
-#endif // SPDLOG_PREVENT_CHILD_FD
-
 // fopen_s on non windows for writing
 SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename_t &mode)
 {
@@ -152,10 +135,19 @@ SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename
 #else
     *fp = ::_fsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
 #endif
+#if defined(SPDLOG_PREVENT_CHILD_FD)
+    if (*fp != nullptr)
+    {
+        auto file_handle = reinterpret_cast<HANDLE>(_get_osfhandle(::_fileno(*fp)));
+        if (!::SetHandleInformation(file_handle, HANDLE_FLAG_INHERIT, 0))
+        {
+            :fclose(*fp);
+            *fp = nullptr;
+        }
+    }
+#endif
 #else // unix
-#if defined(SPDLOG_PREVENT_CHILD_FD) && (defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
-    //  prevent child processes from inheriting log file descriptors direcly on open
-    //  so there is no race with a possible fork and exec
+#if defined(SPDLOG_PREVENT_CHILD_FD)
     const int mode_flag = mode == SPDLOG_FILENAME_T("ab") ? O_APPEND : O_TRUNC;
     const int fd = ::open((filename.c_str()), O_CREAT | O_WRONLY | O_CLOEXEC | mode_flag, mode_t(0644));
     if(fd == -1)
@@ -172,13 +164,6 @@ SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename
 #endif
 #endif
 
-#if defined(SPDLOG_PREVENT_CHILD_FD) && !(defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L)
-    //  prevent child processes from inheriting log file descriptors
-    if (*fp != nullptr)
-    {
-        prevent_child_fd(*fp);
-    }
-#endif
     return *fp == nullptr;
 }
 
diff --git a/include/spdlog/details/os.h b/include/spdlog/details/os.h
index 0894a6c0..8a038b26 100644
--- a/include/spdlog/details/os.h
+++ b/include/spdlog/details/os.h
@@ -38,10 +38,6 @@ static const char folder_sep = '\\';
 SPDLOG_CONSTEXPR static const char folder_sep = '/';
 #endif
 
-#ifdef SPDLOG_PREVENT_CHILD_FD
-void prevent_child_fd(FILE *f);
-#endif
-
 // fopen_s on non windows for writing
 bool fopen_s(FILE **fp, const filename_t &filename, const filename_t &mode);