Function calls in execution contain rich bivariate, hierarchical, and chronological information. Many visualizations have been adopted to analyze function calls in execution for program testing, vulnerability locating, and malware detection. However, we conducted a pilot study and revealed that existing single-viewed function call visualizations fail to present the bivariate, hierarchical, and chronological information comprehensively. A new function call visualization named FCTree is proposed in this work to deal with this situation. Learned from advantages of existing visualizations and iterative discussions with actual users, FCTree uses a compact and aligned hierarchical layout design to present the bivariate and hierarchical information and adopts a glyph design to present the chronological information. Subjective and objective experiments in the laboratory and a field study in a real-world scenario were conducted to evaluate the effectiveness of FCTree.