Macro

Definition

Macro management and expansion core of the fpx Fortran preprocessor.

This module implements a complete, standards-inspired macro system supporting:

• Object-like and function-like macros
• Variadic macros (... and __VA_ARGS__)
• C++20/C23-style __VA_OPT__ handling for optional variadic content
• Parameter stringification (#param) and token pasting (##)
• Built-in predefined macros: __FILE__, __FILENAME__, __LINE__, __DATE__, __TIME__, __TIMESTAMP__, __FUNC__
• Recursive expansion with circular dependency detection via digraph analysis
• Dynamic macro table of macro objects with efficient addition, lookup, removal
• Full support for nested macro calls and proper argument handling

The design allows safe, repeated expansion while preventing infinite recursion. All operations are container-agnostic using allocatable dynamic arrays.

Expansion Model

Macros are expanded recursively. Circular dependencies are detected through dependency graph analysis. Macro lookup is currently linear in the number of defined macros.

Examples

1. Define and use simple macros:

   type(macro), allocatable :: macros(:)
   call add(macros, macro('PI', '3.1415926535'))
   call add(macros, macro('MSG(x)', 'print *, ″Hello ″, x'))
   print *, expand_all(context('area = PI * r**2', 10, './circle.F90', 'circle'), macros, stitch, .false., .false., .true.)
   !> prints: area = 3.1415926535 * r**2

2. Variadic macro with stringification and pasting:

   call add(macros, macro('DEBUG_PRINT(...)', 'print *, ″DEBUG[″, __FILE__, ″:″, __LINE__, ″]: ″, __VA_ARGS__'))
   print *, expand_all(context('DEBUG_PRINT(″value =″, x)', 42, 'test.F90', 'text'), macros, stitch, .false., .false., .true.)
   !> prints: print *, 'DEBUG[', 'test.F90', ':', 42, ']: ', 'value =', x

3. Token pasting with ##:

   call add(macros, macro('MAKE_VAR(name,num)', 'var_name_##num'))
   print *, expand_all(context('real :: MAKE_VAR(temp,42)', 5, 'file.F90', 'file'), macros, stitch, .false., .false.)
   !> prints: real :: var_name_42

Data Types
interface	macro
	Derived type representing a single preprocessor macro Extends string with macro-specific fields: replacement value, parameters, variadic flag, and cyclic self-reference detection. More...
interface	add
	Add one or more macros to a dynamic table. More...
interface	clear
	Remove all macros from a table. More...
interface	get
	Retrieve a macro by index. More...
interface	insert
	Insert more macro to a dynamic table. More...
interface	remove
	Remove a macro at given index. More...
interface	size_of
	Return current number of stored macros. More...

Methods

expand_all()

character(:) function, allocatable, public expand_all	(	type(context), intent(in)	ctx,
		type(macro), dimension(:), intent(inout), allocatable	macros,
		logical, intent(out)	stitch,
		logical, intent(in)	has_extra,
		logical, intent(in)	implicit_conti,
		logical, intent(in)	dollar_insert )

Fully expand a line including predefined macros (FILE, LINE, etc.) First performs normal macro expansion via expand_macros(), then substitutes standard predefined tokens with current file/line/date information.

Parameters

[in]	ctx	Context
[in,out]	macros	Current macro table
[out]	stitch	Set to .true.true. if result ends with '&' (Fortran continuation)
[in]	has_extra	Has extra macros (non-standard) like FILENAME and TIMESTAMP
[in]	implicit_conti	If .true., implicit continuation is permitted
[in]	dollar_insert	If .true., the syntax ${} is supported for macro insertion

Returns

Expanded line with all macros and predefined tokens replaced

Remarks

Definition at line 230 of file macro.f90.

expand_macros()

character(:) function, allocatable, public expand_macros	(	character(*), intent(in)	line,
		type(macro), dimension(:), intent(inout), allocatable	macros,
		logical, intent(out)	stitch,
		logical, intent(in)	implicit_conti,
		logical, intent(in)	dollar_insert,
		type(context), intent(in)	ctx )

Core recursive macro expander (handles function-like, variadic, #, ##).

Performs actual macro replacement with full support for:

• Function-like macros with argument collection
• Stringification (#param)
• Token pasting (##)
• Variadic macros and __VA_ARGS__, __VA_OPT__
• Recursion with cycle detection via digraph
• Proper handling of nested parentheses and quoted strings

Parameters

[in]	line	Line to be expanded
[in,out]	macros	Current macro table
[out]	stitch	.true. if final line ends with '&'
[in]	implicit_conti	If .true., implicit continuation is permitted
[in]	dollar_insert	If .true., ${} macro substitution is supported
[in]	ctx	Context

Returns

Line with user-defined macros expanded (predefined tokens untouched)

Remarks

Definition at line 343 of file macro.f90.

is_defined()

logical function, public is_defined	(	character(*), intent(in)	name,
		type(macro), dimension(:), intent(in)	macros,
		integer, intent(inout), optional	idx )

Check if a macro with given name exists in table.

Parameters

[in]	name	Macro name to test
[in]	macros	Current macro table
[in,out]	idx	Optional: returns index (1-based) if found

Returns

.true. if macro is defined

Remarks

Definition at line 709 of file macro.f90.