Hell Alberto, You are right, realpath() is not defined on stdlib/unistd headers from the g++ compiler used. So, it is not possible to compile the file using this specific compiler :/
Anyway I am trying to compile xerces without this part of code, so I hope it not affects so much. It compiles, but when it links, it shows some error messages like: ld: address 0x39993c of CreateDOMDocument section `.text' is not within region `internal_mem' ld: CreateDOMDocument section `.bootloader' will not fit in region `internal_mem' ld: address 0x425468 of CreateDOMDocument section `.rodata' is not within region `internal_mem' ... I think it is not related to the previous mistake. Thanks for your help.