Compilare: main.c: In function 'read_file': main.c:34:12: warning: passing argument 1 of 'fscanf' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] fscanf(input_file, "%d", a); ^~~~~~~~~~ In file included from /usr/include/features.h:367:0, from /usr/include/stdio.h:27, from main.c:1: /usr/include/stdio.h:443:12: note: expected 'FILE * restrict {aka struct _IO_FILE * restrict}' but argument is of type 'const FILE * {aka const struct _IO_FILE *}' extern int __REDIRECT (fscanf, (FILE *__restrict __stream, ^ main.c:34:5: warning: writing into constant object (argument 3) [-Wformat=] fscanf(input_file, "%d", a); ^~~~~~ main.c:35:12: warning: passing argument 1 of 'fscanf' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] fscanf(input_file, "%d", b); ^~~~~~~~~~ In file included from /usr/include/features.h:367:0, from /usr/include/stdio.h:27, from main.c:1: /usr/include/stdio.h:443:12: note: expected 'FILE * restrict {aka struct _IO_FILE * restrict}' but argument is of type 'const FILE * {aka const struct _IO_FILE *}' extern int __REDIRECT (fscanf, (FILE *__restrict __stream, ^ main.c:35:5: warning: writing into constant object (argument 3) [-Wformat=] fscanf(input_file, "%d", b); ^~~~~~ main.c: In function 'write_file': main.c:41:13: warning: passing argument 1 of 'fprintf' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] fprintf(output_file, "%d", sum); ^~~~~~~~~~~ In file included from /usr/include/stdio.h:936:0, from main.c:1: /usr/include/x86_64-linux-gnu/bits/stdio2.h:95:1: note: expected 'FILE * restrict {aka struct _IO_FILE * restrict}' but argument is of type 'const FILE * {aka const struct _IO_FILE *}' fprintf (FILE *__restrict __stream, const char *__restrict __fmt, ...) ^~~~~~~ main.c: In function 'read_file': main.c:34:5: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(input_file, "%d", a); ^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:35:5: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(input_file, "%d", b); ^~~~~~~~~~~~~~~~~~~~~~~~~~~