Man Page fpp.1
NAME
fpp - the Fortran language preprocessor for FORTRAN 77 and
Fortran 90.
SYNOPSIS
fpp [ options ] [ input-file [ output-file ] ]
DESCRIPTION
fpp is the preprocessor for FORTRAN 77 and Fortran 90.
fpp optionally accepts two filenames as arguments.
input-file and output-file are, respectively, the input
file read and the output file written by the preprocessor.
By default standard input and output are used. fpp should
be used instead of the cpp preprocessor with the Sun FORTRAN
77 compiler.
OPTIONS
-c_com={yes|no}
By default, C style comments are recognized. Turn this
off by specifying -c_com=no
-Dname
Define the preprocessor variable name as 1 (one). This
is the same as if a -Dname=1 option appeared on the fpp
command line, or as if a
#define name 1
line appeared in the source file, which is processed by
fpp.
-Dname=def
Define name as if by a #define directive. This is the
same as if a
#define name def
line appeared in the source file that fpp is process-
ing. The -D option has lower precedence than the -U
option. That is, if the same name is used in both a -U
option and a -D option, the name will be undefined
regardless of the order of the options.
-fixed
Assumes fixed format input source.
-free
Assumes free format input source.
-Idirectory
Insert directory into the search path for #include
files with names not beginning with `/'. directory is
inserted ahead of the standard list of ``include''
directories. Thus, #include files with names enclosed
in double-quotes (") are searched for first in the
directory of the file with the #include line, then in
directories named with -I options, and lastly, in
directories from the standard list. For #include files
with names enclosed in angle-brackets (<>), the direc-
tory of the file with the #include line is not
searched.
-M Generate a list of makefile dependencies and write them
to the standard output. This list indicates that the
object file which would be generated from the input
file depends on the input file as well as the
include files referenced.
-macro={yes|no_com|no}
By default, macros are expanded everywhere. Turn off
macro expansion in comments by specifying -macro=no_com
and turn off macro expansion all together by specifying
-macro=no
-P Do not put line numbering directives to the output
file. This directive appears as
#line-number file-name
-Uname
Remove any initial definition of name, where name is a
fpp variable that is predefined by a particular prepro-
cessor. Here is a partial list of symbols that may be
predefined, depending upon the architecture of the sys-
tem:
Operating System: unix, __unix, and__SVR4
Hardware: sun, __sun, sparc, and__sparc
-undef
Remove initial definitions for all predefined symbols.
-w0 Don't output warnings from fpp to stderr.
-Xu Convert upper-case letters to lower-case, except within
character-string constants. The default is to not con-
vert upper-case letters to lower-case.
-Xw For fixed form source files (See below) fpp assumes
that the symbol ' ' (space) is insignificant. By
default for this form the 'space' symbol is the delim-
iter of tokens.
-Ydirectory
Use the specified directory in place of the standard
list of directories when searching for files.
fpp also understands some FORTRAN 77 compiler options (See
f77(1)):
-e Accept extended source lines, up to 132 characters
long.
-w Do not output warnings to stderr.
USAGE
Source files
fpp operates on both fixed and free form source files. Files
with '.F' extension are assumed to be in fixed form, and
files with '.F90' extensions (and all others) are assumed to
be in free form by default. There is the '-fixed' option for
using fixed form in Fortran 90. fpp recognizes the tab for-
mat of a source line when in fixed mode.
A source file may contain fpp tokens. fpp tokens are close
to those of Fortran. They are:
- fpp directive names.
- symbolic names including Fortran keywords. fpp
permits all symbols in names that Fortran does.
- constants. Integer, real, double and quadruple
precision, binary, octal, hexadecimal including
alternate notation, character and hollerith.
- comments. There are Fortran comments and fpp com-
ments.
- others. Special characters, space, tab, newline,
etc.
Output
Output consists of a modified copy of the input, plus lines
of the form:
#line_number file_name
inserted to indicate the original source line number and
filename of the output line that follows. There is the '-P'
option (See above) which disables the generation of these
lines.
Directives
Syntax and semantics of fpp directives are the same as cpp
directives (See cpp(1)).
All fpp directives start with the hash symbol (#) as the
first character on a line. White space (SPACE or TAB charac-
ters) can appear after the initial '#' for proper indenta-
tion. The directives can be divided into the following
groups:
- macro definitions;
- conditional source code selection;
- inclusion of external files;
- line control.
Macro definition.
The #define directive is used to define both simple string
variables and more complicated macros:
#define name token-string
This is the definition of a fpp variable. Wherever 'name'
appears in the source lines following the definition,
'token-string' will be substituted for 'name'.
#define name(argument [, argument] ... ) token-string
This is the definition of a function-like macro.
Occurrences of the macro 'name' followed by the comma-
separated list of arguments within parentheses are substi-
tuted by the token string produced from the macro defini-
tion. Every occurrence of an argument identifier from the
macro definition's arguments list is substituted by the
token sequence representing the corresponding macro actual
argument.
Macro arguments other than those that are operands of the
macro substitution operators # and ## are expanded recur-
sively prior to their substitution in the replacement token
list.
To allow argument substitution in string literals, use the #
macro substitution operator:
#define a(x) #x
...
a(actual argument)
produces:
'actual argument'
To combine two tokens in a macro definition, one or both of
which is an argument, use the ## macro substitution opera-
tor:
#define cat(x,y) x##y x##b a##y
#define ab ok
...
cat(a,b)
produces:
ok ok ok
In these definitions, spaces between the macro name and the
'(' symbol are prohibited to prevent the directive being
interpreted as a fpp variable definition with the rest of
the line beginning with the '(' symbol being interpreted as
a token-string.
#undef name
Remove any definition for 'name' (produced by 'D' options,
#define directives or by default). No additional tokens are
permitted on the directive line after the name.
Including External Files.
There are two forms of file inclusion:
#include "filename"
#include <filename>
Read in the contents of filename at this location. The lines
read in from the file are processed by fpp as if it were a
part of the current file.
When the <filename> notation is used, filename is only
searched for in the standard ``include'' directories. See
the 'I' and 'Y' options above for more detail. No addi-
tional tokens are permitted in the directive line after the
final `"' or `>'.
Line control.
#line-number "filename" or
#line line-number "filename"
Generate line control information for the next pass of the
compiler. The integer-constant is interpreted as the line
number of the next line and the filename is interpreted
as the name of the file from where it comes. If "filename"
is not given, the current filename is unchanged.
Conditional selection of source text.
There are two forms of conditional selection of source text
1) #if condition_1
block_1
#elif condition_2
block_2
#else
block_n
#endif
2) #ifdef name
block_1
#elif condition
block_2
#else
block_n
#endif
or #ifndef name
block_1
#elif condition
block_2
#else
block_n
#endif
else- and elif-part are optional. There may be more than
one elif-part. Condition is an expression involving fpp con-
stants, macros and intrinsic functions. Condition expres-
sions are similar to cpp expressions, and may contain any
cpp operations and operands with the exception of c long,
octal and hexadecimal constants. Additionally, fpp will
accept and evaluate Fortran logical operations .NOT. .AND.
.OR. .EQV. .NEQV. .GT. .LT. .LE. .GE. etc. and logical con-
stants .TRUE. .FALSE.
Details
Scope of macro or variable definitions.
The scope of a definition begins from the place of its
definition and encloses all the source lines (and source
lines from included files) from that definition line to the
end of the current file.
There are the following exceptions to the scope effected by
an fpp definition:
- files included by Fortran INCLUDE statements;
- fpp and Fortran comments;
- IMPLICIT single letter specifications;
- FORMAT specifications;
- numeric, typeless and character constants.
The scope of the macro effect can be limited by means of the
#undef directive.
End of macro definition
Macro definition can be of any length and is limited only by
the 'newline' symbol. A Macro can be defined in multiple
lines. A Macro can be continued to the next line with the
insertion of '\'. So, the occurrence of a 'newline' without
a macro-continuation signifies the end of the macro defini-
tion.
For example:
#define long_macro_name(x,\
y) x*y
With Fortran 77 fixed form source files, there may be a need
to produce more than one line or statement as the expansion
of a macro. Use the ';' to separate statements that are to
be produced on separate lines:
#define init_i_j(x,y) i=x; j=y
...
init_i_j(1,2)
produces:
i=1
#2
j=2
Function-like macro definition
The number of macro call arguments should be the same as the
number of arguments in the corresponding macro definition.
An error is flagged if they don't.
Cancelling macro definitions of both kinds
#undef name
After this directive, 'name' would not interpreted by fpp
as a macro or variable name. If this name has not been
defined earlier as a macro name, then the given directive
has no effect
Conditional source code selection
- Constant-expression
Subsequent lines up to the matching #else, #elif, or #endif
directive, appear in the output only if their constant-
expression yields a true value.
The lines following the #elif directive appear in the output
only if all of the following conditions hold:
- The constant-expression in the preceding #if
directive evaluated to .FALSE. or the name in the
preceding #ifdef directive is not defined or the
name in the preceding #ifndef directive is
defined.
- The constant-expression in all intervening #elif
directives evaluated to .FALSE.
- The current constant-expression evaluates to
.TRUE.
If the constant-expression evaluates to .TRUE., subse-
quent #elif and #else directives are ignored up to the
matching #endif. Any constant-expression allowed in an #if
directive is allowed in an #elif directive.
The intrinsic function `defined' can be used in a constant-
expression also.
The following items are permitted:
- C language operations: <, >, ==, !=, >=, <=, +, -,
/, *, %, <<, >>, &, ~, |, &&, || They are inter-
preted by fpp in accordance to the C language
semantics (this facility is provided for compati-
bility with "old" Fortran programs using cpp)
- Fortran language operations: .AND., .OR., .NEQV.,
.XOR., .EQV., .NOT. , .GT., .LT., .LE., .GE.,
.NE., .EQ., ** (power).
- Fortran logical constants: .TRUE. , .FALSE.
Only these items, integer constants, and names can be
used within a constant-expression. Names which have not
been defined with the help of the 'D' option, a #define
directive or by default, get 0 as the value. The C
operation '!=' (not equal) can be used in #if or #elif
directive, but NOT in #define directive, where the sym-
bol '!' is considered as the Fortran comment symbol.
#ifdef name
Subsequent lines up to the matching #else, #elif, or
#endif appear in the output only if the name has been
defined, either by a #define directive or by the 'D'
option, and in the absence of an intervening #undef
directive. No additional tokens are permitted on the
directive line after name.
#ifndef name
Subsequent lines up to the matching #else, #elif, or
#endif appear in the output only if name has not been
defined, or if its definition has been removed with an
#undef directive. No additional tokens are permitted
on the directive line after name.
#elif constant-expression .
Any number of #elif directives may appear between an
#if, #ifdef, or #ifndef directive and a matching #else
or #endif directive.
#else
This inverts the sense of the conditional directive
otherwise in effect. If the preceding conditional would
indicate that lines are to be included, then lines
between the #else and the matching #endif are ignored.
If the preceding conditional indicates that lines would
be ignored, subsequent lines are included in the out-
put. Conditional directives and corresponding #else
directives can be nested.
#endif
End a section of lines begun by one of the conditional
directives #if, #ifdef, or #ifndef. Each such direc-
tive must have a matching #endif.
Including External Files
Is the same as it is for cpp. Files are searched as fol-
lows:
for #include "file_name":
- in the directory, in which the processed file has
been found;
- in the directories specified by the -I option;
- in the default directory.
for #include <file_name>:
- in the directories specified by the -I option;
- in the default directory.
fpp directives (beginning with the # symbol in the first
position of lines) can be placed anywhere in a source code,
in particular before a Fortran continuation line. The only
exception is the prohibition of fpp directives within a
macro call divided on several lines by means of continuation
symbols.
Comments
fpp permits comments of two kinds:
1) Fortran language comments. A source line containing one
of the symbols 'C', 'c', '*', 'd' or 'D' in the first posi-
tion, is considered as a comment line. Within such lines
macro expansions are not performed. The '!' symbol is
interpreted as the beginning of a comment extending to the
end of the line. The only exception is the case when this
symbol occurs within a constant-expression in #if and #elif
directives (See above).
2) fpp comments enclosed in the '/*' and '*/' parasymbols.
They are excluded from the output and macro expansions are
not performed within these symbols. fpp comments can be
nested and for each parasymbol '/*' there must be a
corresponding parasymbol '*/'. fpp comments are suitable
for excluding the compilation of large portions of source
instead of commenting every line with Fortran comment sym-
bols.
Intrinsic functions
The intrinsic function
defined(name) or defined name
Returns:
.TRUE. - if name is defined as a macro.
.FALSE.- if the name is not defined.
Macro expansion
If, during expansion of a macro, the column width of a line
exceeds column 72 (for the fixed format) or column 132 (for
the free format), fpp inserts appropriate continuation
lines.
In the fixed form there is limitation on macro expansions in
label fields (positions 1-5):
- a macro call (together with possible arguments)
should not extend more than the column 5 position;
- a macro call whose name begins with one of the
Fortran comment symbols is considered as a part of
a comment;
- a macro expansion may produce a text extending
beyond the column 5 position. In such a case a
warning will be issued.
In the fixed form when the '-Xw' option has been specified
an ambiguity may appear if a macro call occurs in a state-
ment position and a macro name begins or coincides with a
Fortran keyword. For example, in the following text:
#define callp(x) call f(x)
call p(0)
fpp can not determine with certainty how to interpret the
'call p' token sequence. It could be considered as a macro
name. The current implementation does the following:
- the longer identifier is chosen (callp in this
case);
- from this identifier the longest macro name or
keyword is extracted;
- if a macro name has been extracted a macro expan-
sion is performed. If the name begins with some
keyword fpp outputs an appropriate warning;
- the rest of the identifier is considered as a
whole identifier.
In the above example the macro expansion would be performed
and the following warning would be output:
warning: possibly incorrect substitution of macro callp
It should be noted that this situation appears only when
preprocessing a fixed format source code and when the space
symbol is not interpreted as a token delimiter. It should
be said also that if a macro name coincides with a keyword
beginning part, as in the following case:
#define INT INTEGER*8
INTEGER k
then in accordance with the described algorithm, the INTEGER
keyword will be found earlier than the INT macro name. Thus,
there will be no warning when preprocessing such a macro
definition.
DIAGNOSTICS
There are three kinds of diagnostic messages:
- warnings. preprocessing of source code is contin-
ued and the return value remains to be 0.
- errors. fpp continues preprocessing but sets the
return code to a nonzero value, namely number of
errors.
- fatal error. fpp cancels preprocessing and
returns a nonzero return value.
The messages produced by fpp are intended to be self-
explanatory. The line number and filename where the error
occurred are printed along with the diagnostic.
SEE ALSO
cpp(1), f77(1), f90(1)
The source code for fpp is downloadable from NetLib
http://www.netlib.org/fortran/