AutoreleasePoolSnapshot.m

//
//  ObjectsSnapshot.m
//  MRMail
//
//  Created by Nikolay Morev on 02/02/16.
//  Copyright © 2016 Mail.Ru. All rights reserved.
//

#import "ObjectsSnapshot.h"
#include <stdio.h>

static NSString * captureStderrWithBlock(void (^block)(void));
static NSString * captureShowPools(void);

static NSString * _objectsSnapshot = nil;
static void * _ignoredPointers[1000] = { NULL };
NSString * MRObjectsSnapshotAndSave(void) {
    _objectsSnapshot = captureShowPools();
    return _objectsSnapshot;
}

NSString * MRObjectsSnapshotAndCompare(void) {
    NSString *snapshot = captureShowPools();

    NSArray *before = [_objectsSnapshot componentsSeparatedByString:@"\n"];
    NSArray *after = [snapshot componentsSeparatedByString:@"\n"];

    NSMutableSet *afterSet = [NSMutableSet setWithArray:after];
    [afterSet minusSet:[NSSet setWithArray:before]];

    __block BOOL (^predicateBlock)(NSString *, NSDictionary *);
    predicateBlock = ^BOOL (NSString *string, NSDictionary *bindings) {
        BOOL ignored = ([string containsString:@"releases pending"] ||
                        [string containsString:@"_XCTestCaseImplementation"] ||
                        [string containsString:[NSString stringWithFormat:@"%p", _objectsSnapshot]] ||
                        [string containsString:[NSString stringWithFormat:@"%p", predicateBlock]] ||
                        [string containsString:@"__NSMallocBlock__"]);
        for (int i = 0; i < 1000; i++) {
            void *p = _ignoredPointers[i];
            if (p == NULL) {
                break;
            }
            ignored = ignored || [string containsString:[NSString stringWithFormat:@"%p", p]];
        }
        return !ignored;
    };
    NSArray *diff = [[afterSet allObjects] filteredArrayUsingPredicate:
                     [NSPredicate predicateWithBlock:predicateBlock]];

    _ignoredPointers[0] = NULL;

    return [diff componentsJoinedByString:@"\n"];
}

static NSString * captureShowPools(void) {
    void (^block)(void) = ^{
        Class pool = NSClassFromString(@"NSAutoreleasePool");
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
        [pool performSelector:NSSelectorFromString(@"showPools")];
#pragma clang diagnostic pop
    };
    _ignoredPointers[0] = (__bridge void *)block;
    return captureStderrWithBlock(block);
}

static NSString * captureStderrWithBlock(void (^block)(void)) {
    FILE *output;
    NSString *filePath;
    @autoreleasepool {
        NSString *directory = NSTemporaryDirectory();
        filePath = [directory stringByAppendingPathComponent:@"stdout.log"];
        output = fopen([filePath fileSystemRepresentation], "w");
    }

    int fileno = STDERR_FILENO;

    int saved_stdout;
    saved_stdout = dup(fileno);
    dup2(output->_file, fileno);

    _ignoredPointers[1] = (__bridge void *)filePath;
    _ignoredPointers[2] = (__bridge void *)block;
    _ignoredPointers[3] = NULL;

    block();

    dup2(saved_stdout, fileno);
    close(saved_stdout);
    fclose(output);

    NSData *data = [[NSData alloc] initWithContentsOfFile:filePath];
    NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return string;
}