Compilare: main.cpp: In constructor 'buffered_reader<buffer_size>::buffered_reader(FILE*) [with long unsigned int buffer_size = 5000ul]': main.cpp:13:9: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer, 1, buffer_size, instream); ^~~~~ main.cpp: In member function 'void buffered_reader<buffer_size>::shift() [with long unsigned int buffer_size = 5000ul]': main.cpp:15:42: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] void shift(){p++; if(p==buffer_size) p=0,fread(buffer, 1, buffer_size, instream);} ^