Just note for those who might be in the same situation as I was in, since this took me so much hours to resolve...
I encountered this error after I used Find/Replace functionality in Xcode. The problem is that some characters are "overreplaced" due to my carelessness (i.e. replace not only the relevant parts but also the redundant parts) and thus some of variables become undefined ones. Nonetheless those undefined variables weren't caught in the compile (even after making a clean) and finally the signal segmentation error was displayed on the screen.