Exim coding style

Preferred C coding style, in order to match that used in most of the rest of the project:

• C89 standard 'C' with limited C99 later features listed here:
  • designated initializers, for struct/union/array elements. Use whereever possible.
  • loop-variable declared in "for"
• variables
  • No non-block-head variable declarations (except as already permitted)
  • generally, declare in the smallest scope possible
  • Use the "uschar" type for chars
  • Use the BOOL type for general booleans
• 2-space indent, 8-space hard tabs
• 80-char line max. Continuation lines indented
• Code-block braces align vertically and are indented
• Toplevel code in functions is zero-indented
• In conditions
  • use boolean variables directly - do not compare against TRUE or FALSE.
  • test pointers for (non)NULL by treating as boolean
  • complex conditionals have subclases vertically aligned and indented
  • assignments used also as conditionals are encouraged where it makes code tighter, but must be parethesized
• if-else has the else aligned with the if
• Inline block comments
  • blankline-separated from code
  • generally describe reasoning for subsequent code
  • align with code and do not put asterix on continuation lines.
• Block comments on functions
  • left-aligned
  • describe purpose of function
  • list arguments with purpose, and describe return value
• Functions
  • return type on separate line
  • use "static" return type wherever possible
  • functions written purely to make codeflow more clear are permissable, even if used only once
• Use the project memory-allocation methods, not direct malloc
• Use the project string-manipulation facilities

Note that these are guidelines only, and variation is permissable when there is specific reason.