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scope::guard(3) [osx man page]

Scope::Guard(3) 					User Contributed Perl Documentation					   Scope::Guard(3)

Scope::Guard - lexically-scoped resource management SYNOPSIS
my $guard = guard { ... }; # or my $guard = scope_guard &handler; # or my $guard = Scope::Guard->new(sub { ... }); $guard->dismiss(); # disable the handler DESCRIPTION
This module provides a convenient way to perform cleanup or other forms of resource management at the end of a scope. It is particularly useful when dealing with exceptions: the "Scope::Guard" constructor takes a reference to a subroutine that is guaranteed to be called even if the thread of execution is aborted prematurely. This effectively allows lexically-scoped "promises" to be made that are automatically honoured by perl's garbage collector. For more information, see: <> METHODS
new my $guard = Scope::Guard->new(sub { ... }); # or my $guard = Scope::Guard->new(&handler); The "new" method creates a new "Scope::Guard" object which calls the supplied handler when its "DESTROY" method is called, typically at the end of the scope. dismiss $guard->dismiss(); # or $guard->dismiss(1); "dismiss" detaches the handler from the "Scope::Guard" object. This revokes the "promise" to call the handler when the object is destroyed. The handler can be re-enabled by calling: $guard->dismiss(0); EXPORTS
guard "guard" takes a block and returns a new "Scope::Guard" object. It can be used as a shorthand for: Scope::Guard->new(...) e.g. my $guard = guard { ... }; Note: calling "guard" anonymously, i.e. in void context, will raise an exception. This is because anonymous guards are destroyed immediately (rather than at the end of the scope), which is unlikely to be the desired behaviour. scope_guard "scope_guard" is the same as "guard", but it takes a code ref rather than a block. e.g. my $guard = scope_guard &handler; or: my $guard = scope_guard sub { ... }; or: my $guard = scope_guard $handler; As with "guard", calling "scope_guard" in void context will raise an exception. VERSION
o B::Hooks::EndOfScope o End o Guard o Hook::Scope o Object::Destroyer o Perl::AtEndOfScope o ReleaseAction o Scope::local_OnExit o Scope::OnExit o Sub::ScopeFinalizer o Value::Canary AUTHOR
chocolateboy <> COPYRIGHT
Copyright (c) 2005-2010, chocolateboy. This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself. perl v5.16.2 2010-05-16 Scope::Guard(3)

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PTHREAD_ATTR_SETGUARDSIZE(3)				     Linux Programmer's Manual				      PTHREAD_ATTR_SETGUARDSIZE(3)

pthread_attr_setguardsize, pthread_attr_getguardsize - set/get guard size attribute in thread attributes object SYNOPSIS
#include <pthread.h> int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize); int pthread_attr_getguardsize(pthread_attr_t *attr, size_t *guardsize); Compile and link with -pthread. DESCRIPTION
The pthread_attr_setguardsize() function sets the guard size attribute of the thread attributes object referred to by attr to the value specified in guardsize. If guardsize is greater than 0, then for each new thread created using attr the system allocates an additional region of at least guardsize bytes at the end of the thread's stack to act as the guard area for the stack (but see BUGS). If guardsize is 0, then new threads created with attr will not have a guard area. The default guard size is the same as the system page size. If the stack address attribute has been set in attr (using pthread_attr_setstack(3) or pthread_attr_setstackaddr(3)), meaning that the caller is allocating the thread's stack, then the guard size attribute is ignored (i.e., no guard area is created by the system): it is the application's responsibility to handle stack overflow (perhaps by using mprotect(2) to manually define a guard area at the end of the stack that it has allocated). The pthread_attr_getguardsize() function returns the guard size attribute of the thread attributes object referred to by attr in the buffer pointed to by guardsize. RETURN VALUE
On success, these functions return 0; on error, they return a nonzero error number. ERRORS
POSIX.1-2001 documents an EINVAL error if attr or guardsize is invalid. On Linux these functions always succeed (but portable and future- proof applications should nevertheless handle a possible error return). VERSIONS
These functions are provided by glibc since version 2.1. CONFORMING TO
A guard area consists of virtual memory pages that are protected to prevent read and write access. If a thread overflows its stack into the guard area, then, on most hard architectures, it receives a SIGSEGV signal, thus notifying it of the overflow. Guard areas start on page boundaries, and the guard size is internally rounded up to the system page size when creating a thread. (Nevertheless, pthread_attr_getguardsize() returns the guard size that was set by pthread_attr_setguardsize().) Setting a guard size of 0 may be useful to save memory in an application that creates many threads and knows that stack overflow can never occur. Choosing a guard size larger than the default size may be necessary for detecting stack overflows if a thread allocates large data struc- tures on the stack. BUGS
As at glibc 2.8, the NPTL threading implementation includes the guard area within the stack size allocation, rather than allocating extra space at the end of the stack, as POSIX.1 requires. (This can result in an EINVAL error from pthread_create(3) if the guard size value is too large, leaving no space for the actual stack.) The obsolete LinuxThreads implementation did the right thing, allocating extra space at the end of the stack for the guard area. EXAMPLE
See pthread_getattr_np(3). SEE ALSO
mmap(2), mprotect(2), pthread_attr_init(3), pthread_attr_setstack(3), pthread_attr_setstacksize(3), pthread_create(3), pthreads(7) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at Linux 2008-10-24 PTHREAD_ATTR_SETGUARDSIZE(3)
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