Hi, i second tomás' assessment and proposal.
Reco wrote: > #include with encased in 'less' and 'more' characters instructs > preprocessor to search header files system-wide. A search path can be > modified with -L flag. It is not a system-wide search, but rather a search iterating over a list of directory prefixes: https://gcc.gnu.org/onlinedocs/cpp/Include-Syntax.html That's why i agree with tomás that e.g. /usr/include/openssl/md5.h should be used like #include <openssl/md5.h> because i expect that /usr/include is in the prefix list. gcc -L is for libraries (-l): https://gcc.gnu.org/onlinedocs/gcc-4.9.3/gcc/Directory-Options.html#Directory-Options Own include directories are added by -I for #include <...> or -iquote for $include "..." > #include with quotes instructs preprocessor to search a header file in > the current directory. But if not found there, the prefix list is searched, too. Have a nice day :) Thomas