Fix up and namespace clock_gettime and clock_getres for MacOS

Summary:
Resolve two issues with folly's clock_gettime() shim on Apple platforms (iOS, macOS, etc.):

When detecting whether folly should define clock_gettime() on Apple platforms, don't assume clock_gettime() is declared in Apple's headers just because MAC_OS_X_VERSION_10_12/__IPHONE_10_0 is defined. Someone might use a newer macOS or iOS SDK (which defines MAC_OS_X_VERSION_10_12/__IPHONE_10_0), but not have clock_gettime() (because _DARWIN_FEATURE_CLOCK_GETTIME isn't set).

When defining a shim for clock_gettime(), don't rely on Apple's clock_gettime() declaration. Instead, shadow Apple's declaration with our own. This prevents folly from inheriting Apple's availability and visibility attributes for clock_gettime().

Reviewed By: yfeldblum

Differential Revision: D5312574

fbshipit-source-id: f16634ce92ee6c299613d3db22f0537bd31ac14d

diff --git a/folly/portability/Time.cpp b/folly/portability/Time.cpp
index 54b3d0a10f0ac9d93045fea4494483f0a19f5261..e54286fe30893400cd6e40b36c5d0e8481795147 100644 (file)
--- a/folly/portability/Time.cpp
+++ b/folly/portability/Time.cpp
@@ -43,6 +43,10 @@ static void duration_to_ts(
 #include <mach/thread_act.h>
 #include <mach/vm_map.h>
 
+namespace folly {
+namespace portability {
+namespace time {
+
 static std::chrono::nanoseconds time_value_to_ns(time_value_t t) {
   return std::chrono::seconds(t.seconds) +
       std::chrono::microseconds(t.microseconds);
@@ -136,6 +140,10 @@ int clock_getres(clockid_t clk_id, struct timespec* ts) {
 
   return 0;
 }
+
+} // namespace time
+} // namespace portability
+} // namespace folly
 #elif defined(_WIN32)
 #include <errno.h>
 #include <locale.h>
@@ -144,6 +152,10 @@ int clock_getres(clockid_t clk_id, struct timespec* ts) {
 
 #include <folly/portability/Windows.h>
 
+namespace folly {
+namespace portability {
+namespace time {
+
 using unsigned_nanos = std::chrono::duration<uint64_t, std::nano>;
 
 static unsigned_nanos filetimeToUnsignedNanos(FILETIME ft) {
@@ -272,6 +284,10 @@ extern "C" int clock_gettime(clockid_t clock_id, struct timespec* tp) {
       return -1;
   }
 }
+
+} // namespace time
+} // namespace portability
+} // namespace folly
 #else
 #error No clock_gettime(3) compatibility wrapper available for this platform.
 #endif

diff --git a/folly/portability/Time.h b/folly/portability/Time.h
index eb6c7941c19eabbeedcf2b0c5764707821da4549..a7e5cf2da932e1d30904b34d5c536bdc5d35727a 100644 (file)
--- a/folly/portability/Time.h
+++ b/folly/portability/Time.h
@@ -20,6 +20,7 @@
 #include <time.h>
 
 #include <folly/portability/Config.h>
+#include <folly/Portability.h>
 
 // OSX is a pain. The XCode 8 SDK always declares clock_gettime
 // even if the target OS version doesn't support it, so you get
@@ -27,15 +28,10 @@
 // solve that by pretending we have it here in the header and
 // then enable our implementation on the source side so that
 // gets linked in instead.
-#if __MACH__ &&                                                \
+#if __MACH__ && FOLLY_HAVE_CLOCK_GETTIME &&                    \
     (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12 || \
      __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_10_0)
 
-#ifdef FOLLY_HAVE_CLOCK_GETTIME
-#undef FOLLY_HAVE_CLOCK_GETTIME
-#endif
-
-#define FOLLY_HAVE_CLOCK_GETTIME 1
 #define FOLLY_FORCE_CLOCK_GETTIME_DEFINITION 1
 
 #endif
@@ -47,10 +43,25 @@
 #define CLOCK_MONOTONIC 1
 #define CLOCK_PROCESS_CPUTIME_ID 2
 #define CLOCK_THREAD_CPUTIME_ID 3
+#endif
 
+#if (!FOLLY_HAVE_CLOCK_GETTIME || FOLLY_FORCE_CLOCK_GETTIME_DEFINITION) && (defined(__MACH__) || defined(_WIN32))
+namespace folly {
+namespace portability {
+namespace time {
 typedef uint8_t clockid_t;
-extern "C" int clock_gettime(clockid_t clk_id, struct timespec* ts);
-extern "C" int clock_getres(clockid_t clk_id, struct timespec* ts);
+int clock_gettime(clockid_t clk_id, struct timespec* ts);
+int clock_getres(clockid_t clk_id, struct timespec* ts);
+}
+}
+}
+
+FOLLY_PUSH_WARNING
+#if __CLANG_PREREQ(3, 0)
+FOLLY_GCC_DISABLE_WARNING("-Wheader-hygiene")
+#endif
+/* using override */ using namespace folly::portability::time;
+FOLLY_POP_WARNING
 #endif
 
 #ifdef _WIN32