Handle system time sampling failures safely.

public/client/TracySysTime.cpp

@@ -26,7 +26,7 @@ static inline uint64_t ConvertTime( const FILETIME& t )
     return ( uint64_t( t.dwHighDateTime ) << 32 ) | uint64_t( t.dwLowDateTime );
 }
 
-void SysTime::ReadTimes()
+bool SysTime::ReadTimes()
 {
     FILETIME kernelTime;
     FILETIME userTime;
@@ -35,13 +35,13 @@ void SysTime::ReadTimes()
     FILETIME creationTime;
     FILETIME exitTime;
 
-    GetProcessTimes( GetCurrentProcess(), &creationTime, &exitTime, &kernelTime, &userTime );
+    if( !GetProcessTimes( GetCurrentProcess(), &creationTime, &exitTime, &kernelTime, &userTime ) ) return false;
 
     idle = 0;
 #    else
     FILETIME idleTime;
 
-    GetSystemTimes( &idleTime, &kernelTime, &userTime );
+    if( !GetSystemTimes( &idleTime, &kernelTime, &userTime ) ) return false;
 
     idle = ConvertTime( idleTime );
 #    endif
@@ -49,52 +49,58 @@ void SysTime::ReadTimes()
     const auto kernel = ConvertTime( kernelTime );
     const auto user = ConvertTime( userTime );
     used = kernel + user;
+    return true;
 }
 
 #  elif defined __linux__
 
-void SysTime::ReadTimes()
+bool SysTime::ReadTimes()
 {
-    uint64_t user, nice, system;
+    uint64_t user, nice, system, idleTicks;
     FILE* f = fopen( "/proc/stat", "r" );
-    if( f )
-    {
-        int read = fscanf( f, "cpu %" PRIu64 " %" PRIu64 " %" PRIu64" %" PRIu64, &user, &nice, &system, &idle );
-        fclose( f );
-        if (read == 4)
-        {
-            used = user + nice + system;
-        }
-    }
+    if( !f ) return false;
+
+    const int read = fscanf( f, "cpu %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64, &user, &nice, &system, &idleTicks );
+    fclose( f );
+    if( read != 4 ) return false;
+
+    used = user + nice + system;
+    idle = idleTicks;
+    return true;
 }
 
 #  elif defined __APPLE__
 
-void SysTime::ReadTimes()
+bool SysTime::ReadTimes()
 {
     host_cpu_load_info_data_t info;
     mach_msg_type_number_t cnt = HOST_CPU_LOAD_INFO_COUNT;
-    host_statistics( mach_host_self(), HOST_CPU_LOAD_INFO, reinterpret_cast<host_info_t>( &info ), &cnt );
+    if( host_statistics( mach_host_self(), HOST_CPU_LOAD_INFO, reinterpret_cast<host_info_t>( &info ), &cnt ) != KERN_SUCCESS ) return false;
     used = info.cpu_ticks[CPU_STATE_USER] + info.cpu_ticks[CPU_STATE_NICE] + info.cpu_ticks[CPU_STATE_SYSTEM];
     idle = info.cpu_ticks[CPU_STATE_IDLE];
+    return true;
 }
 
 #  elif defined __FreeBSD__ || defined __NetBSD__ || defined __OpenBSD__ || defined __DragonFly__
 
-void SysTime::ReadTimes()
+bool SysTime::ReadTimes()
 {
     u_long data[5];
     size_t sz = sizeof( data );
-    sysctlbyname( "kern.cp_time", &data, &sz, nullptr, 0 );
+    if( sysctlbyname( "kern.cp_time", &data, &sz, nullptr, 0 ) != 0 ) return false;
     used = data[0] + data[1] + data[2] + data[3];
     idle = data[4];
+    return true;
 }
 
 #endif
 
 SysTime::SysTime()
+    : idle( 0 )
+    , used( 0 )
+    , haveBaseline( false )
 {
-    ReadTimes();
+    haveBaseline = ReadTimes();
 }
 
 float SysTime::Get()
@@ -102,7 +108,16 @@ float SysTime::Get()
     const auto oldUsed = used;
     const auto oldIdle = idle;
 
-    ReadTimes();
+    if( !ReadTimes() )
+    {
+        haveBaseline = false;
+        return -1;
+    }
+    else if( !haveBaseline )
+    {
+        haveBaseline = true;
+        return -1;
+    }
 
     const auto diffIdle = idle - oldIdle;
     const auto diffUsed = used - oldUsed;

public/client/TracySysTime.hpp

@@ -18,10 +18,11 @@ public:
     SysTime();
     float Get();
 
-    void ReadTimes();
-
 private:
+    bool ReadTimes();
+
     uint64_t idle, used;
+    bool haveBaseline;
 };
 
 }