fpt Reference: cpp Commands

fpt and WinFPT Reference Manual - Command-line Commands

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HIDE CPP EMULATE CPP SHOW CPP

Syntax:

HIDE CPP EMULATE CPP SHOW CPP

cpp in Fortran

Some Fortran codes must be pre-processed before they can be built. Pre-processing is carried out, for example, to select facilities supported by some but not all compilers, or to configure the code for different parallel configurations. The most widely used pre-processor is the C pre-processor, cpp. cpp is usually used to process free format Fortran code. cpp changes the code layout, and this may disrupt the organisation of fixed format code.

The fpt implementation of cpp

WinFPT and fpt handle cpp macros and constructs in the same way as cpp itself, with the following exceptions:

The # character which introduces cpp commands must be written in column 1. This conforms to the -traditional switch to cpp. This is the normal usage for Fortran code, because it prevents accidental interpretation of # characters in comments and strings.
Lines are not inserted into the code to indicate the current file. By default, cpp inserts lines, introduced by # characters, which are used by the C compiler to provide debugging information. These lines cause compilation errors in Fortran. Under cpp they are suppressed by the comand-line switch -P.
C-style comments in the code are not suppressed. By default, cpp strips C coments. This is unlikely to be a problem in Fortran for the block comments between /* and */ delimiters. However, the Fortran string concatenation operator, // could be handled as a C comment delimiter. The behaviour is the same as that produced by the cpp command switch -C.
The cpp token concatenation operator, ## is handled in the same way as in cpp, even though cpp does not process this construct when -traditional is specified. It is therefore possible to use cpp macros in fpt to construct and modify tokens.
The spacing of tokens is not changed by the fpt implementation of cpp. cpp compresses white space to a single space character.
No warning is issued if a macro definition is changed. By default, cpp issues a warning if a macro is changed without an intervening #undef command.

fpt processes the cpp macros and commands and then analyses and re-engineers the resulting Fortran code. Therefore fpt cannot analyse and re-engineer the unused branches of #if constructs. These are reproduced as text exactly as they are written in the original code. Operatons like rename symbol must therefore be used with care when cpp contructs are present.

Function of the Commands:

HIDE CPP commands fpt to analyse and re-engineer the Fortran code generated from the cpp commands, but to re-write the code with the commands and macros in place. The code produced may therefore be built by the original build procedure for the program, with the cpp operations unchanged. Care must be taken to avoid unexpected side effects from renumbering labels, renaming variables and changing file names.

EMULATE CPP commands fpt to write the code which would be generated by cpp. Any engineering changes made by fpt, and any diagnostic messages, are also written in the output files. This code is expected to be fully compilable. The cpp commands are removed and processing by cpp is no longer necessary in the build. However it is not possible to rebuild with different cpp options. This command is particularly useful when code is inspected interactively. It is possible to toggle between the three cpp handling options in interactive mode.

SHOW CPP commands fpt to show both the macros and the macro expansions in the code. Any engineering changes made by fpt, and any diagnostic messages, are also written in the output. This code will not compile. The facility is useful when code is examined interactively.

The command SHOW CPP MACROS displays and alphabetical list of the cpp macros defined in the program.

Where to use these commands:

Operating system command line	Yes
Configuration file, config.fsp	Yes
Specification (fsp) files, *.fsp	Yes
Interactively, to FPT> prompt	Yes
Interactive command files	Yes
Embedded in the Fortran code	Yes

Default

HIDE CPP

Examples

The same code fragment is displayed interactively with the three different cpp command settings:

FPT> hide cpp FPT> type 21 14 ! 15 #define FTYPE yield 16 #define ROUTINE set_components 17 CALL ROUTINE(FTYPE%name,val_name,FTYPE%value,val_val, & 18 FTYPE%description,val_description) 19 #undef ROUTINE 20 ! 21 >>#define ROUTINE get_components 22 CALL ROUTINE(FTYPE%name,val_name,FTYPE%value,val_val, & 23 FTYPE%description,val_description) 24 #undef ROUTINE 25 ! 26 #define ROUTINE show_components 27 CALL ROUTINE(FTYPE%name,val_name,FTYPE%value,val_val, & 28 FTYPE%description,val_description) 29 #undef ROUTINE FPT> FPT> emulate cpp FPT> type 21 14 ! 15 16 17 CALL set_components(yield%name,val_name,yield%value,val_val, & 18 yield%description,val_description) 19 20 ! 21 >> 22 CALL get_components(yield%name,val_name,yield%value,val_val, & 23 yield%description,val_description) 24 25 ! 26 27 CALL show_components(yield%name,val_name,yield%value,val_val, & 28 yield%description,val_description) 29 ! FPT> FPT> show cpp FPT> type 21 14 ! 15 !CPP! #define FTYPE yield 16 !CPP! #define ROUTINE set_components 17 CALL ROUTINE << set_components >> (FTYPE << yield >> %name, & 18 val_name,FTYPE << yield >> %value,val_val,FTYPE << yield >> % & 18 description,val_description) 19 !CPP! #undef ROUTINE 20 ! 21 >>!CPP! #define ROUTINE get_components 22 CALL ROUTINE << get_components >> (FTYPE << yield >> %name, & 23 val_name,FTYPE << yield >> %value,val_val,FTYPE << yield >> % & 23 description,val_description) 24 !CPP! #undef ROUTINE 25 ! 26 !CPP! #define ROUTINE show_components 27 CALL ROUTINE << show_components >> (FTYPE << yield >> %name, & 28 val_name,FTYPE << yield >> %value,val_val,FTYPE << yield >> % & 28 description,val_description) 29 !CPP! #undef ROUTINE