Indenting #defines

Question

I know that #defines, etc. are normally never indented. Why?

I\'m working in some code at the moment which has a horrible mixture of #define

Answer 1

As some have already said, some Pre-ANSI compilers required the # to be the first char on the line but they didn't require de preprocessor directive to be attached to it, so indentation was made this way.

#ifdef SDCC
#  if DEBUGGING == 1
#    if defined (pic18f2480)
#      define FLASH_MEMORY_END 0x3DC0
#    elif defined (pic18f2580)
#      define FLASH_MEMORY_END 0x7DC0
#    else
#      error "Can't set  up flash memory end!"
#    endif
#  else
#    if defined (pic18f2480)
#      define FLASH_MEMORY_END 0x4000
#    elif defined (pic18f2580)
#      define FLASH_MEMORY_END 0x8000
#    else
#      error "Can't set  up flash memory end!"
#    endif
#  endif
#else
#  if DEBUGGING == 1
#    define FLASH_MEMORY_END 0x7DC0
#  else
#    define FLASH_MEMORY_END 0x8000
#  endif
#endif

I've often seen this style in old Unix headers but I hate it as the syntax coloring often fails on such code. I use a very visible color for pre-processor directive so that they stand out (they are at a meta-level so should not be part of the normal flow of code). You can even see that SO does not color the sequence in a useful manner.