Define

Definition

Processing of define and undef preprocessor directives This module implements the core logic for handling macro definition and removal during preprocessing in the fpx Fortran preprocessor. It supports:

• Object-like macros: #define NAME value
• Function-like macros: #define NAME(arg1, arg2, ...) replacement
• Variadic macros using ... and automatic detection
• Proper parameter parsing with whitespace handling
• Macro redefinition (overwrites existing definition)
• Safe #undef that removes a previously defined macro
• Integration with global undef list (globalundef) to block redefinition
• Comprehensive verbose logging of all definition actions

The routines are designed to be robust against malformed input and provide clear diagnostics when verbose = .true..

Examples

1. Define simple object-like macros:

   #define PI 3.141592653589793
   #define DEBUG 1
   #define MAX_SIZE 1024
   ...

2. Define function-like and variadic macros:

   #define SQR(x) ((x)*(x))
   #define LOG_MSG(level, ...)  print *, '[LOG:', level, ']', __VA_ARGS__
   #define CONCAT(a,b) a ## _ ## b
   ...

3. Undefine a macro:

   #undef DEBUG
   !> Subsequent #ifdef DEBUG will be false

4. Using from a driver program:

   use fpx_global
   use fpx_logging, only: verbose
    
   verbose = .true.
   call preprocess('input.F90')   ! Will show all macro definitions/undefs
   ...

Methods

handle_define()

subroutine, public handle_define	(	type(context), intent(in)	ctx,
		type(macro), dimension(:), intent(inout), allocatable	macros,
		character(*), intent(in)	token )

Process a define directive and register or update a macro Parses the line after #define, distinguishes between object-like and function-like forms, handles variadic ..., extracts parameters correctly, and stores the macro in the active macro table. Existing macros are overwritten. Respects globalundef list – macros listed there are ignored.

Parameters

[in]	ctx	Context source line containing the define
[in,out]	macros	Current macro table (updated in-place)
[in]	token	Usually 'DEFINE' – keyword matched in lowercase

Remarks

Definition at line 77 of file define.f90.

handle_undef()

subroutine, public handle_undef	(	type(context), intent(in)	ctx,
		type(macro), dimension(:), intent(inout), allocatable	macros,
		character(*), intent(in)	token )

Process a undef directive and remove a macro from the table Finds the named macro in the current table and removes it. Issues a warning if the macro was not previously defined.

Parameters

[in]	ctx	Context source line containing the undef
[in,out]	macros	Current macro table (updated in-place)
[in]	token	Usually 'UNDEF' – keyword matched in lowercase

Remarks

Definition at line 207 of file define.f90.