Program received signal SIGSEGV, Segmentation fault. strlen () at ../sysdeps/x86_64/strlen.S:106 106 ../sysdeps/x86_64/strlen.S: No such file or directory. (gdb) bt #0 strlen () at ../sysdeps/x86_64/strlen.S:106 #1 0x00005555555b3afe in xstrdup () #2 0x000055555556325d in register_redirection () #3 0x00005555555932ad in retrieve_url () #4 0x0000555555591621 in res_retrieve_file () #5 0x0000555555590132 in download_child () #6 0x000055555558f7c4 in retrieve_tree () #7 0x000055555558b47c in main ()