Localizing bugs is important, difficult, and expensive, especially for large software projects. To address this problem, information retrieval (IR) based bug localization has increasingly been used to suggest potential buggy files given a bug report. To date, researchers have proposed a number of IR techniques for bug localization and empirically evaluated them to understand their effectiveness. However, virtually all of the evaluations have been limited to the projects written in object-oriented programming languages, particularly Java. Therefore, the effectiveness of these techniques for other widely-used languages such as C is still unknown. In this paper, we create a benchmark dataset consisting of more than 7,500 bug reports from five popular C projects and rigorously evaluate our recently introduced IR-based bug localization tool using this dataset. Our results indicate that although the IR-relevant properties of C and Java programs are different, IR-based bug localization in C software at the file level is overall as effective as in Java software. However, we also find that the recent advance of using program structure information in performing bug localization gives less of a benefit for C software than for Java software.