Previous: Traditional Scheduling, Up: Priority [Contents][Index]

• Gnu C Library On Mac Windows 10
• Gnu C Standard Library
• Gnu Math Library
• Gnu C++ Download For Windows

22.3.5 Limiting execution to certain CPUs

1. The GNU C library includes several header files, each of which provides definitions and declarations for a group of related facilities; this information is used by the C compiler when processing your program.
2. GNU C library (glibc) is one of the most important components of GNU Hurd and most modern GNU/Linux distributions. It is used by almost all C programs and provides the most essential APIs, including the C standard library and other standard libraries.
3. Download Mac software in the Libraries category - Page 6. Secure and fast web browser that comes with all the necessary tools and features to fulfill all your Internet browsing needs, improve your overall browsing experience and replace Safari on your Mac.
4. The GNU C Library, commonly known as glibc, is the GNU Project's implementation of the C standard library. Despite its name, it now also directly supports C (and, indirectly, other programming languages). It was started in the early 1990s by the Free Software Foundation (FSF) for their GNU operating system.
5. What C library version does my system use? Ask Question Asked 6 years ago. Nice answers, but no one addresses how to do this on a Mac, where there is no ldd.version GNU C Library (GNU libc) stable release version 2.18, by Roland McGrath et al.

Apr 25, 2016  Sounds like you've got an environment problem. Given that you've installed it a couple times, it's probably somewhere on your system. GCC is just being misdirected as to where it is. I don't know what you've done installing it these different ways.

On a multi-processor system the operating system usually distributesthe different processes which are runnable on all available CPUs in away which allows the system to work most efficiently. Which processesand threads run can be to some extend be control with the schedulingfunctionality described in the last sections. But which CPU finallyexecutes which process or thread is not covered.

There are a number of reasons why a program might want to have controlover this aspect of the system as well:

• One thread or process is responsible for absolutely critical workwhich under no circumstances must be interrupted or hindered frommaking progress by other processes or threads using CPU resources. Inthis case the special process would be confined to a CPU which noother process or thread is allowed to use.
• The access to certain resources (RAM, I/O ports) has different costsfrom different CPUs. This is the case in NUMA (Non-Uniform MemoryArchitecture) machines. Preferably memory should be accessed locallybut this requirement is usually not visible to the scheduler.Therefore forcing a process or thread to the CPUs which have localaccess to the most-used memory helps to significantly boost theperformance.
• In controlled runtimes resource allocation and book-keeping work (forinstance garbage collection) is performance local to processors. Thiscan help to reduce locking costs if the resources do not have to beprotected from concurrent accesses from different processors.

The POSIX standard up to this date is of not much help to solve thisproblem. The Linux kernel provides a set of interfaces to allowspecifying affinity sets for a process. The scheduler willschedule the thread or process on CPUs specified by the affinitymasks. The interfaces which the GNU C Library define follow to someextent the Linux kernel interface.

This data set is a bitset where each bit represents a CPU. How thesystem’s CPUs are mapped to bits in the bitset is system dependent.The data type has a fixed size; in the unlikely case that the numberof bits are not sufficient to describe the CPUs of the system adifferent interface has to be used.

This type is a GNU extension and is defined in sched.h.

To manipulate the bitset, to set and reset bits, a number of macros aredefined. Some of the macros take a CPU number as a parameter. Hereit is important to never exceed the size of the bitset. The followingmacro specifies the number of bits in the cpu_set_t bitset.

The value of this macro is the maximum number of CPUs which can behandled with a cpu_set_t object.

The type cpu_set_t should be considered opaque; allmanipulation should happen via the next four macros.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This macro initializes the CPU set set to be the empty set.

This macro is a GNU extension and is defined in sched.h.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This macro adds cpu to the CPU set set.

The cpu parameter must not have side effects since it isevaluated more than once.

This macro is a GNU extension and is defined in sched.h.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This macro removes cpu from the CPU set set.

The cpu parameter must not have side effects since it isevaluated more than once.

This macro is a GNU extension and is defined in sched.h.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This macro returns a nonzero value (true) if cpu is a memberof the CPU set set, and zero (false) otherwise.

The cpu parameter must not have side effects since it isevaluated more than once.

This macro is a GNU extension and is defined in sched.h.

CPU bitsets can be constructed from scratch or the currently installedaffinity mask can be retrieved from the system.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This function stores the CPU affinity mask for the process or threadwith the ID pid in the cpusetsize bytes long bitmappointed to by cpuset. If successful, the function alwaysinitializes all bits in the cpu_set_t object and returns zero.

If pid does not correspond to a process or thread on the systemthe or the function fails for some other reason, it returns -1and errno is set to represent the error condition.

No process or thread with the given ID found.

The pointer cpuset does not point to a valid object.

This function is a GNU extension and is declared in sched.h.

Note that it is not portably possible to use this information toretrieve the information for different POSIX threads. A separateinterface must be provided for that.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

This function installs the cpusetsize bytes long affinity maskpointed to by cpuset for the process or thread with the ID pid.If successful the function returns zero and the scheduler will in the futuretake the affinity information into account.

If the function fails it will return -1 and errno is setto the error code:

No process or thread with the given ID found.

The pointer cpuset does not point to a valid object.

The bitset is not valid. This might mean that the affinity set mightnot leave a processor for the process or thread to run on.

This function is a GNU extension and is declared in sched.h.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

The getcpu function identifies the processor and node on whichthe calling thread or process is currently running and writes them intothe integers pointed to by the cpu and node arguments. Theprocessor is a unique nonnegative integer identifying a CPU. The nodeis a unique nonnegative integer identifying a NUMA node. When eithercpu or node is NULL, nothing is written to therespective pointer.

The return value is 0 on success and -1 on failure. Thefollowing errno error condition is defined for this function:

The operating system does not support this function.

This function is Linux-specific and is declared in sched.h.

Previous: Traditional Scheduling, Up: Priority [Contents][Index]

Previous: Setting an Alarm, Up: Date and Time [Contents][Index]

21.7 Sleeping

Gnu C Library On Mac Windows 10

The function sleep gives a simple way to make the program waitfor a short interval. If your program doesn’t use signals (except toterminate), then you can expect sleep to wait reliably throughoutthe specified interval. Otherwise, sleep can return sooner if asignal arrives; if you want to wait for a given interval regardless ofsignals, use select (see Waiting for I/O) and don’t specifyany descriptors to wait for.

Preliminary: MT-Unsafe sig:SIGCHLD/linux AS-Unsafe AC-Unsafe See POSIX Safety Concepts.

The sleep function waits for seconds seconds or until a signalis delivered, whichever happens first.

You can delete the whole CoreSimulator/ directory. Xcode will recreate fresh instances there for you when you do your next simulator run. If you can afford losing any previous simulator data of your apps this is the easy way to get space. Mac library developer coresimulator.

If sleep returns because the requested interval is over,it returns a value of zero. If it returns because of delivery of asignal, its return value is the remaining time in the sleep interval.

The sleep function is declared in unistd.h.

Resist the temptation to implement a sleep for a fixed amount of time byusing the return value of sleep, when nonzero, to callsleep again. This will work with a certain amount of accuracy aslong as signals arrive infrequently. But each signal can cause theeventual wakeup time to be off by an additional second or so. Suppose afew signals happen to arrive in rapid succession by bad luck—there isno limit on how much this could shorten or lengthen the wait.

Instead, compute the calendar time at which the program should stopwaiting, and keep trying to wait until that calendar time. This won’tbe off by more than a second. With just a little more work, you can useselect and make the waiting period quite accurate. (Of course,heavy system load can cause additional unavoidable delays—unless themachine is dedicated to one application, there is no way you can avoidthis.)

On some systems, sleep can do strange things if your program usesSIGALRM explicitly. Even if SIGALRM signals are beingignored or blocked when sleep is called, sleep mightreturn prematurely on delivery of a SIGALRM signal. If you haveestablished a handler for SIGALRM signals and a SIGALRMsignal is delivered while the process is sleeping, the action takenmight be just to cause sleep to return instead of invoking yourhandler. And, if sleep is interrupted by delivery of a signalwhose handler requests an alarm or alters the handling of SIGALRM,this handler and sleep will interfere.

On GNU systems, it is safe to use sleep and SIGALRM inthe same program, because sleep does not work by means ofSIGALRM.

Preliminary: MT-Safe AS-Safe AC-Safe See POSIX Safety Concepts.

If resolution to seconds is not enough the nanosleep function canbe used. As the name suggests the sleep interval can be specified innanoseconds. The actual elapsed time of the sleep interval might belonger since the system rounds the elapsed time you request up to thenext integer multiple of the actual resolution the system can deliver.

*requested_time is the elapsed time of the interval you want tosleep.

The function returns as *remaining the elapsed time left in theinterval for which you requested to sleep. If the interval completedwithout getting interrupted by a signal, this is zero.

struct timespec is described in Time Types.

Gnu C Standard Library

If the function returns because the interval is over the return value iszero. If the function returns -1 the global variable errnois set to the following values:

The call was interrupted because a signal was delivered to the thread.If the remaining parameter is not the null pointer the structurepointed to by remaining is updated to contain the remainingelapsed time. Where are arduino libraries stored on mac.

Gnu Math Library

The nanosecond value in the requested_time parameter contains anillegal value. Either the value is negative or greater than or equal to1000 million.

This function is a cancellation point in multi-threaded programs. Thisis a problem if the thread allocates some resources (like memory, filedescriptors, semaphores or whatever) at the time nanosleep iscalled. If the thread gets canceled these resources stay allocateduntil the program ends. To avoid this calls to nanosleep shouldbe protected using cancellation handlers.

Gnu C++ Download For Windows

The nanosleep function is declared in time.h.

Previous: Setting an Alarm, Up: Date and Time [Contents][Index]