今天遇到一个坑
在 用Xtrace 分析MJRefresh代码的时候，由于对NSLog进行宏定义

#define NSLog(FORMAT, ...) fprintf(stderr,"\nfunction:%s line:%d content:%s\n", __FUNCTION__, __LINE__, [[NSString stringWithFormat:FORMAT, ##__VA_ARGS__] UTF8String]);

然而

 for ( int l=0 ; l<levels ; l++ ) {

        if ( !swizzledClasses[aClass] && !exists( excludedClasses, aClass ) ) {
            unsigned mc = 0;
            const char *className = class_getName(aClass);
            Method *methods = class_copyMethodList(aClass, &mc);

           for( unsigned i=0; methods && i<mc; i++ ) {
                const char *type = method_getTypeEncoding(methods[i]);
                const char *name = sel_getName(method_getName(methods[i]));
                [nameStr appendFormat:@"%s", name];

                if ( ((includeMethods && ![self string:nameStr matches:includeMethods]) ||
                      (excludeMethods && [self string:nameStr matches:excludeMethods])) )
                   ;//NSLog( @"Xtrace: filters exclude: %s[%s %s] %s", mtype, className, name, type );

                else if ( (excludeTypes && [self string:[NSString stringWithUTF8String:type] matches:excludeTypes]) )
                    NSLog( @"Xtrace: type filter excludes: %s[%s %s] %s", mtype, className, name, type );

                else if ( name[0] == '.' ||
                         [nameStr isEqualToString:@"description"] || [nameStr hasPrefix:@"_description"] ||
                         [nameStr isEqualToString:@"retain"] || [nameStr isEqualToString:@"release"] /*||
                         [nameStr isEqualToString:@"dealloc"] || [nameStr hasPrefix:@"_dealloc"]*/ )
                    ; // best avoided

#ifdef __IPHONE_OS_VERSION_MIN_REQUIRED
                else if ( aClass == [UIView class] && [nameStr isEqualToString:@"drawRect:"] )
                    ; // no idea why this is a problem...
#endif

                else if (params.includeProperties || !class_getProperty( aClass, name ))
                    [self intercept:aClass method:methods[i] mtype:mtype depth:depth];

               [nameStr setString:@""];
            }

            swizzledClasses[aClass] = YES;
            free( methods );
        }

        aClass = class_getSuperclass(aClass);
        if ( !--depth || aClass == nsObject || aClass == nsObjectMeta ) // don't trace NSObject
            break;
    }

上面这段代码 每个if-else 后面没有大括号{},会出现问题。