madler/pigz — pull request #7 by gnu-user (2013-06-03 03:47:43+00:00)
Title: Added -lm to Makefile, which is required for some systems

I ran into issues trying to compile pigz on some Redhat 6 systems using GCC 4.5.3, adding **-lm** for the math library functions used in tree.c was all that was required for it to build properly.