What is the meaning of lines starting with a hash sign and number like ‘# 1 “a.c”‘ in the gcc preprocessor output?

by

These lines are hints for debugging (where the code following the line actually came from)

# line-number "source-file" [flags]

Meaning of flags (space separated):

  • 1 – Start of a new file
  • 2 – Returning to previous file
  • 3 – Following text comes from a system header file (#include <> vs #include “”)
  • 4 – Following text should be treated as being wrapped in an implicit extern “C” block.

More Related Contents:

  1. Why does the C preprocessor interpret the word “linux” as the constant “1”?
  2. Finding out what the GCC include path is [duplicate]
  3. C preprocessor: expand macro in a #warning
  4. Can’t compile C program on a Mac after upgrade to Mojave
  5. Is there a 128 bit integer in gcc?
  6. Can I use Intel syntax of x86 assembly with GCC?
  7. Disable all optimization options in GCC
  8. Is errno thread-safe?
  9. What is the meaning of “__attribute__((packed, aligned(4))) “
  10. Embedding binary blobs using gcc mingw
  11. Tell gcc to specifically unroll a loop
  12. Can I mix static and shared-object libraries when linking?
  13. #ifdef inside #define
  14. Disable variable-length automatic arrays in gcc
  15. Is there a good reason for always enclosing a define in parentheses in C?
  16. Why can’t local variable be used in GNU C basic inline asm statements?
  17. Create statically-linked binary that uses getaddrinfo?
  18. Fused multiply add and default rounding modes
  19. Yet Another MinGW “gcc: error: CreateProcess: No such file or directory”
  20. An alternative for the deprecated __malloc_hook functionality of glibc
  21. Standard C library in mingW
  22. Pointer arithmetic when void has unknown size [closed]
  23. Should variable definition be in header files?
  24. How to get the size of a C function from inside a C program or with inline assembly?
  25. Why is execstack required to execute code on the heap?
  26. gcc detect duplicate symbols/functions in static libraries
  27. GCC – no warning about an uninitialized array with -O0
  28. Order of fields when using a bit field in C
  29. How much overhead can the -fPIC flag add?
  30. conflicting types error when compiling c program using gcc

Leave a Comment