Unable to reproduce. (After adding in #include and a main() ... since you omitted them in your non-compilable-as-is example.) I tried -DSIZE=1 through -DSIZE=20000. What operating system are you using (e.g., FreeBSD, Ubuntu, Plan 9, Herd, OS/2, Amiga OS)? What architecture are you using (e.g., SPARC, i686, PowerPC, 680x0)? What compiler version are you using (e.g., GCC 4.1.1 is current, 4.2.0 is nearing release, 4.0.3 is previous, anything before 4.0 is closed)? How are you compling the code? Provide the command line verbatim. --Eljay