What is this double curly brace in C, Objective-C

Question

In reference to this source code what is the purpose of the double curly braces within the @autoreleasepool?

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        {{
            assert([EnumWith1ConstantSansExplicitValuesByLabel() count] == 1);
            assert([[EnumWith1ConstantSansExplicitValuesByLabel() objectForKey:@"EnumWith1ConstantSansExplicitValues_Constant1"] isEqual:[NSNumber numberWithInt:0]]);

            assert([EnumWith1ConstantSansExplicitValuesByValue() count] == 1);
            assert([[EnumWith1ConstantSansExplicitValuesByValue() objectForKey:[NSNumber numberWithInt:0]] isEqual:@"EnumWith1ConstantSansExplicitValues_Constant1"]);

            EnumWith1ConstantSansExplicitValues a = 0;

            assert(EnumWith1ConstantSansExplicitValues_Constant1 == a);
            assert([@"EnumWith1ConstantSansExplicitValues_Constant1" isEqualToString:EnumWith1ConstantSansExplicitValuesToString(a)]);
            assert(EnumWith1ConstantSansExplicitValuesFromString(EnumWith1ConstantSansExplicitValuesToString(EnumWith1ConstantSansExplicitValues_Constant1), &a));
            assert(EnumWith1ConstantSansExplicitValues_Constant1 == a);

            a++;
            assert([@"<unknown EnumWith1ConstantSansExplicitValues: 1>" isEqualToString:EnumWith1ConstantSansExplicitValuesToString(a)]);
            assert(!EnumWith1ConstantSansExplicitValuesFromString(@"foo", &a));
        }}
        {{
            assert([EnumWith1ConstantSansExplicitValuesTrailingCommaByLabel() count] == 1);
        }}
    ...
    printf("success\n");
    return 0;
}

Answer 1

There is nothing special about the double-curly-braces*. It's just used by the authors to logically separate sections of code within a rather long method.

*: Beyond the single-curly-brace behavior of declaring a scope block.