iPhone的堆栈大小是否固定?

问题描述：

当我尝试调整线程的堆栈大小时:

When I am trying to adjust of stack size of threads:

- (void)testStack:(NSInteger)n {
    NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(dummy) object:nil];
    NSUInteger size = 4096 * n;
    [thread setStackSize:size];
    [thread start];
}

- (void)dummy {
    NSUInteger bytes = [[NSThread currentThread] stackSize];
    NSLog(@"%@", @(bytes));
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    for (NSInteger i = 126; i <= 130; i++) {
        [self testStack:i];
    }
    return YES;
}

在输出中，大小不变:

2015-06-19 11:05:06.912 Stack[52982:2082454] 524288
2015-06-19 11:05:06.913 Stack[52982:2082457] 524288
2015-06-19 11:05:06.913 Stack[52982:2082456] 524288
2015-06-19 11:05:06.913 Stack[52982:2082458] 524288
2015-06-19 11:05:06.913 Stack[52982:2082455] 524288

iPhone堆栈大小是否固定?

is the iPhone stack size fixed?

p.s.我正在iPhone 6 Plus调试模式下测试以上内容.

p.s. I am testing the above in iPhone 6 Plus, debug mode.

更新:在MacBook上的Simulator中运行时，可以调整堆栈:

UPDATE: the stack can be adjusted when running in the Simulator on MacBook:

2015-06-19 11:25:17.042 Stack[1418:427993] 528384
2015-06-19 11:25:17.042 Stack[1418:427994] 532480
2015-06-19 11:25:17.042 Stack[1418:427992] 524288
2015-06-19 11:25:17.042 Stack[1418:427991] 520192
2015-06-19 11:25:17.042 Stack[1418:427990] 516096

答

堆栈大小受设备限制，在大多数情况下，iPhone OS上的主线程不能超过1MB，也不能缩小.

The stack size is bounded on the device, and in most cases cannot exceed 1MB for the main thread on iPhone OS, nor can it be shrunk.

辅助线程允许的最小堆栈大小为16 KB，并且堆栈大小必须为4 KB的倍数.在线程创建时会在进程空间中预留该内存的空间，但是直到需要它们时，才会创建与该内存关联的实际页面.

The minimum allowed stack size for secondary threads is 16 KB and the stack size must be a multiple of 4 KB. The space for this memory is set aside in your process space at thread creation time, but the actual pages associated with that memory are not created until they are needed.

iPhone的堆栈大小是否固定?

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