When I tried to compile skipfish on my Debian stable system I noticed it had no "configure" script, so I worried it won't have all required libraries etc.. And exactly that was the case, I got this error:
http_client.c:39:18: error: idna.h: No such file or directory http_client.c: In function 'parse_url': http_client.c:286: warning: implicit declaration of function 'idna_to_ascii_8z' http_client.c:286: error: 'IDNA_SUCCESS' undeclared (first use in this function) http_client.c:286: error: (Each undeclared identifier is reported only once http_client.c:286: error: for each function it appears in.) make: *** [skipfish] Error 1
Thankfully it was easy to fix, it's just missing some dependencies like dev version of libidn11 so I installed it with couple other packages and then the program compiled correctly.
sudo apt-get install libidn11-dev libssl-dev zlibc