117 lines
4.0 KiB
C
117 lines
4.0 KiB
C
|
//
|
||
|
|
// EXTScope.h
|
||
|
|
// extobjc
|
||
|
|
//
|
||
|
|
// Created by Justin Spahr-Summers on 2011-05-04.
|
||
|
|
// Copyright (C) 2012 Justin Spahr-Summers.
|
||
|
|
// Released under the MIT license.
|
||
|
|
//
|
||
|
|
|
||
|
|
#import <WMF/metamacros.h>
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \@onExit defines some code to be executed when the current scope exits. The
|
||
|
|
* code must be enclosed in braces and terminated with a semicolon, and will be
|
||
|
|
* executed regardless of how the scope is exited, including from exceptions,
|
||
|
|
* \c goto, \c return, \c break, and \c continue.
|
||
|
|
*
|
||
|
|
* Provided code will go into a block to be executed later. Keep this in mind as
|
||
|
|
* it pertains to memory management, restrictions on assignment, etc. Because
|
||
|
|
* the code is used within a block, \c return is a legal (though perhaps
|
||
|
|
* confusing) way to exit the cleanup block early.
|
||
|
|
*
|
||
|
|
* Multiple \@onExit statements in the same scope are executed in reverse
|
||
|
|
* lexical order. This helps when pairing resource acquisition with \@onExit
|
||
|
|
* statements, as it guarantees teardown in the opposite order of acquisition.
|
||
|
|
*
|
||
|
|
* @note This statement cannot be used within scopes defined without braces
|
||
|
|
* (like a one line \c if). In practice, this is not an issue, since \@onExit is
|
||
|
|
* a useless construct in such a case anyways.
|
||
|
|
*/
|
||
|
|
#define onExit \
|
||
|
|
ext_keywordify \
|
||
|
|
__strong ext_cleanupBlock_t metamacro_concat(ext_exitBlock_, __LINE__) __attribute__((cleanup(ext_executeCleanupBlock), unused)) = ^
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Creates \c __weak shadow variables for each of the variables provided as
|
||
|
|
* arguments, which can later be made strong again with #strongify.
|
||
|
|
*
|
||
|
|
* This is typically used to weakly reference variables in a block, but then
|
||
|
|
* ensure that the variables stay alive during the actual execution of the block
|
||
|
|
* (if they were live upon entry).
|
||
|
|
*
|
||
|
|
* See #strongify for an example of usage.
|
||
|
|
*/
|
||
|
|
#define weakify(...) \
|
||
|
|
ext_keywordify \
|
||
|
|
metamacro_foreach_cxt(ext_weakify_,, __weak, __VA_ARGS__)
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Like #weakify, but uses \c __unsafe_unretained instead, for targets or
|
||
|
|
* classes that do not support weak references.
|
||
|
|
*/
|
||
|
|
#define unsafeify(...) \
|
||
|
|
ext_keywordify \
|
||
|
|
metamacro_foreach_cxt(ext_weakify_,, __unsafe_unretained, __VA_ARGS__)
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Strongly references each of the variables provided as arguments, which must
|
||
|
|
* have previously been passed to #weakify.
|
||
|
|
*
|
||
|
|
* The strong references created will shadow the original variable names, such
|
||
|
|
* that the original names can be used without issue (and a significantly
|
||
|
|
* reduced risk of retain cycles) in the current scope.
|
||
|
|
*
|
||
|
|
* @code
|
||
|
|
|
||
|
|
id foo = [[NSObject alloc] init];
|
||
|
|
id bar = [[NSObject alloc] init];
|
||
|
|
|
||
|
|
@weakify(foo, bar);
|
||
|
|
|
||
|
|
// this block will not keep 'foo' or 'bar' alive
|
||
|
|
BOOL (^matchesFooOrBar)(id) = ^ BOOL (id obj){
|
||
|
|
// but now, upon entry, 'foo' and 'bar' will stay alive until the block has
|
||
|
|
// finished executing
|
||
|
|
@strongify(foo, bar);
|
||
|
|
|
||
|
|
return [foo isEqual:obj] || [bar isEqual:obj];
|
||
|
|
};
|
||
|
|
|
||
|
|
* @endcode
|
||
|
|
*/
|
||
|
|
#define strongify(...) \
|
||
|
|
ext_keywordify \
|
||
|
|
_Pragma("clang diagnostic push") \
|
||
|
|
_Pragma("clang diagnostic ignored \"-Wshadow\"") \
|
||
|
|
metamacro_foreach(ext_strongify_,, __VA_ARGS__) \
|
||
|
|
_Pragma("clang diagnostic pop")
|
||
|
|
|
||
|
|
/*** implementation details follow ***/
|
||
|
|
typedef void (^ext_cleanupBlock_t)(void);
|
||
|
|
|
||
|
|
void ext_executeCleanupBlock (__strong ext_cleanupBlock_t *block);
|
||
|
|
|
||
|
|
#define ext_weakify_(INDEX, CONTEXT, VAR) \
|
||
|
|
CONTEXT __typeof__(VAR) metamacro_concat(VAR, _weak_) = (VAR);
|
||
|
|
|
||
|
|
#define ext_strongify_(INDEX, VAR) \
|
||
|
|
__strong __typeof__(VAR) VAR = metamacro_concat(VAR, _weak_);
|
||
|
|
|
||
|
|
// Details about the choice of backing keyword:
|
||
|
|
//
|
||
|
|
// The use of @try/@catch/@finally can cause the compiler to suppress
|
||
|
|
// return-type warnings.
|
||
|
|
// The use of @autoreleasepool {} is not optimized away by the compiler,
|
||
|
|
// resulting in superfluous creation of autorelease pools.
|
||
|
|
//
|
||
|
|
// Since neither option is perfect, and with no other alternatives, the
|
||
|
|
// compromise is to use @autorelease in DEBUG builds to maintain compiler
|
||
|
|
// analysis, and to use @try/@catch otherwise to avoid insertion of unnecessary
|
||
|
|
// autorelease pools.
|
||
|
|
#if DEBUG
|
||
|
|
#define ext_keywordify autoreleasepool {}
|
||
|
|
#else
|
||
|
|
#define ext_keywordify try {} @catch (...) {}
|
||
|
|
#endif
|