POSIX: Remove use of deprecated gettimeofday

POSIX.1-2008 deprecated gettimeofday, which we used as a fallback if the
monotonic clock was unavailable.

This replaces that fallback with the non-monotonic real-time clock.

Because of the Gordian knot of feature test macros across Unices, this
also includes the shift from some platform source files defining
_POSIX_C_SOURCE to various values to _DEFAULT_SOURCE being defined for
all source files on Linux.  This is because -std=c99 on Linux disables
_DEFAULT_SOURCE (POSIX 2008 and extensions).

Once runtime platform selection comes in, this kind of platform-specific
preprocessor logic can be moved into the platform glue files and won't
need to be replicated by third-party build setups, but for now, sorry.

README.md

@@ -236,6 +236,7 @@ information on what to include when reporting a bug.
  - [Wayland] Bugfix: Client-Side Decorations were destroyed in the wrong worder
    (#1798)
  - [Wayland] Bugfix: Monitors physical size could report zero (#1784,#1792)
+ - [POSIX] Removed use of deprecated function `gettimeofday`
  - [POSIX] Bugfix: `CLOCK_MONOTONIC` was not correctly tested for or enabled
  - [NSGL] Removed enforcement of forward-compatible flag for core contexts
  - [NSGL] Bugfix: `GLFW_COCOA_RETINA_FRAMEBUFFER` had no effect on newer

src/CMakeLists.txt

@@ -190,6 +190,13 @@ if (MSVC90)
     endif()
 endif()
 
+# Workaround for -std=c99 on Linux disabling _DEFAULT_SOURCE (POSIX 2008 and more)
+if (_GLFW_X11 OR _GLFW_WAYLAND OR _GLFW_OSMESA)
+    if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+        target_compile_definitions(glfw PRIVATE _DEFAULT_SOURCE)
+    endif()
+endif()
+
 if (BUILD_SHARED_LIBS)
     if (WIN32)
         if (MINGW)

src/posix_time.c

@@ -27,13 +27,10 @@
 // It is fine to use C99 in this file because it will not be built with VS
 //========================================================================
 
-#define _POSIX_C_SOURCE 199309L
-
 #include "internal.h"
 
 #include <unistd.h>
 #include <sys/time.h>
-#include <time.h>
 
 
 //////////////////////////////////////////////////////////////////////////
@@ -44,20 +41,14 @@
 //
 void _glfwInitTimerPOSIX(void)
 {
-#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+    _glfw.timer.posix.clock = CLOCK_REALTIME;
-    struct timespec ts;
-
-    if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
-    {
-        _glfw.timer.posix.monotonic = GLFW_TRUE;
     _glfw.timer.posix.frequency = 1000000000;
-    }
+
-    else
+#if defined(_POSIX_MONOTONIC_CLOCK)
+    struct timespec ts;
+    if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
+        _glfw.timer.posix.clock = CLOCK_MONOTONIC;
 #endif
-    {
-        _glfw.timer.posix.monotonic = GLFW_FALSE;
-        _glfw.timer.posix.frequency = 1000000;
-    }
 }
 
 
@@ -66,22 +57,11 @@ void _glfwInitTimerPOSIX(void)
 //////////////////////////////////////////////////////////////////////////
 
 uint64_t _glfwPlatformGetTimerValue(void)
-{
-#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
-    if (_glfw.timer.posix.monotonic)
 {
     struct timespec ts;
-        clock_gettime(CLOCK_MONOTONIC, &ts);
+    clock_gettime(_glfw.timer.posix.clock, &ts);
     return (uint64_t) ts.tv_sec * (uint64_t) 1000000000 + (uint64_t) ts.tv_nsec;
 }
-    else
-#endif
-    {
-        struct timeval tv;
-        gettimeofday(&tv, NULL);
-        return (uint64_t) tv.tv_sec * (uint64_t) 1000000 + (uint64_t) tv.tv_usec;
-    }
-}
 
 uint64_t _glfwPlatformGetTimerFrequency(void)
 {

src/posix_time.h

@@ -28,13 +28,14 @@
 #define _GLFW_PLATFORM_LIBRARY_TIMER_STATE _GLFWtimerPOSIX posix
 
 #include <stdint.h>
+#include <time.h>
 
 
 // POSIX-specific global timer data
 //
 typedef struct _GLFWtimerPOSIX
 {
-    GLFWbool    monotonic;
+    clockid_t   clock;
     uint64_t    frequency;
 
 } _GLFWtimerPOSIX;

src/wl_init.c

@@ -26,8 +26,6 @@
 // It is fine to use C99 in this file because it will not be built with VS
 //========================================================================
 
-#define _POSIX_C_SOURCE 200809L
-
 #include "internal.h"
 
 #include <assert.h>
@@ -1297,10 +1295,8 @@ void _glfwPlatformTerminate(void)
 const char* _glfwPlatformGetVersionString(void)
 {
     return _GLFW_VERSION_NUMBER " Wayland EGL OSMesa"
-#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+#if defined(_POSIX_MONOTONIC_CLOCK)
-        " clock_gettime"
+        " monotonic"
-#else
-        " gettimeofday"
 #endif
         " evdev"
 #if defined(_GLFW_BUILD_DLL)

src/x11_init.c

@@ -1484,10 +1484,8 @@ void _glfwPlatformTerminate(void)
 const char* _glfwPlatformGetVersionString(void)
 {
     return _GLFW_VERSION_NUMBER " X11 GLX EGL OSMesa"
-#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+#if defined(_POSIX_MONOTONIC_CLOCK)
-        " clock_gettime"
+        " monotonic"
-#else
-        " gettimeofday"
 #endif
 #if defined(__linux__)
         " evdev"