What are these unfamiliar lines in a preprocessed C file?

Question

This is the output of GNU cpp in the Hello World C program. I wonder what these lines mean? # Number Header_File_Location [Numbers]

# 1 "hello.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "hello.c"
# 1 "/usr/include/stdio.h" 1 3 4
# 27 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/features.h" 1 3 4
# 374 "/usr/include/features.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 1 3 4
# 385 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
# 386 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 2 3 4
# 375 "/usr/include/features.h" 2 3 4
# 398 "/usr/include/features.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 1 3 4
# 10 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/gnu/stubs-64.h" 1 3 4
# 11 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4
# 399 "/usr/include/features.h" 2 3 4
# 28 "/usr/include/stdio.h" 2 3 4





# 1 "/usr/lib/gcc/x86_64-linux-gnu/4.8/include/stddef.h" 1 3 4
# 212 "/usr/lib/gcc/x86_64-linux-gnu/4.8/include/stddef.h" 3 4
typedef long unsigned int size_t;
# 34 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/include/x86_64-linux-gnu/bits/types.h" 1 3 4
# 27 "/usr/include/x86_64-linux-gnu/bits/types.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
# 28 "/usr/include/x86_64-linux-gnu/bits/types.h" 2 3 4


typedef unsigned char __u_char;
typedef unsigned short int __u_short;
typedef unsigned int __u_int;
typedef unsigned long int __u_long;

Are these any dependencies? If so, then what? Line numbers?

Answer 1

This is a line number directive and tells the compiler which line and file contains the next part of the source in translation units .

The way the compiler can report errors in the included header files after preprocessing.

Answer 2

gcc :

 # linenum filename flags

. ( ). , file filename linenum. ; .

, , "1", "2", "3", "4. , . :

'1 .

'2 ( ).

'3 , , .

'4 , extern" C".