Over the last years, an increasing number of safety-critical tasks have been demanded to computer systems. In particular, safety-critical computer-based applications are hitting market area where cost is a major issue, and thus solutions are required which conjugate fault tolerance with low costs. In this paper, a source-to-source compiler supporting a Software-Implemented Hardware Fault Tolerance approach is proposed, based on a set of source code transformation rules. The proposed approach hardens a program against transient memory errors by introducing software redundancy: every computation is performed twice and results are compared, and control-flow invariants are checked explicitly. By exploiting the tool's capabilities, several benchmark applications have been hardened against transient errors. Fault Injection campaigns have been performed to evaluate the fault detection capability of the hardened applications. In addition we analyzed the proposed approach in terms of space and time overheads.