NAME
fort77 - FORTRAN compiler (FORTRAN)
SYNOPSIS
fort77 [-c][-g][-L directory]... [-O optlevel][-o outfile][-s][-w]
operand...
DESCRIPTION
The fort77 utility is the interface to the FORTRAN compilation system;
it shall accept the full FORTRAN-77 language defined by the
ANSI X3.9-1978 standard. The system conceptually consists of a compiler
and link editor. The files referenced by operands are compiled and
linked to produce an executable file. It is unspecified whether the
linking occurs entirely within the operation of fort77; some
implementations may produce objects that are not fully resolved until
the file is executed.
If the -c option is present, for all pathname operands of the form file
.f, the files:
$(basename pathname.f).o
shall be created or overwritten as the result of successful
compilation. If the -c option is not specified, it is unspecified
whether such .o files are created or deleted for the file .f operands.
If there are no options that prevent link editing (such as -c) and all
operands compile and link without error, the resulting executable file
shall be written into the file named by the -o option (if present) or
to the file a.out. The executable file shall be created as specified
in the System Interfaces volume of IEEE Std 1003.1-2001, except that
the file permissions shall be set to:
S_IRWXO | S_IRWXG | S_IRWXU
and that the bits specified by the umask of the process shall be
cleared.
OPTIONS
The fort77 utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines, except
that:
* The -l library operands have the format of options, but their
position within a list of operands affects the order in which
libraries are searched.
* The order of specifying the multiple -L options is significant.
* Conforming applications shall specify each option separately; that
is, grouping option letters (for example, -cg) need not be
recognized by all implementations.
The following options shall be supported:
-c Suppress the link-edit phase of the compilation, and do not
remove any object files that are produced.
-g Produce symbolic information in the object or executable files;
the nature of this information is unspecified, and may be
modified by implementation-defined interactions with other
options.
-s Produce object or executable files, or both, from which symbolic
and other information not required for proper execution using
the exec family of functions defined in the System Interfaces
volume of IEEE Std 1003.1-2001 has been removed (stripped). If
both -g and -s options are present, the action taken is
unspecified.
-o outfile
Use the pathname outfile, instead of the default a.out, for the
executable file produced. If the -o option is present with -c,
the result is unspecified.
-L directory
Change the algorithm of searching for the libraries named in -l
operands to look in the directory named by the directory
pathname before looking in the usual places. Directories named
in -L options shall be searched in the specified order. At least
ten instances of this option shall be supported in a single
fort77 command invocation. If a directory specified by a -L
option contains a file named libf.a, the results are
unspecified.
-O optlevel
Specify the level of code optimization. If the optlevel option-
argument is the digit ’0’ , all special code optimizations shall
be disabled. If it is the digit ’1’ , the nature of the
optimization is unspecified. If the -O option is omitted, the
nature of the system’s default optimization is unspecified. It
is unspecified whether code generated in the presence of the -O
0 option is the same as that generated when -O is omitted. Other
optlevel values may be supported.
-w Suppress warnings.
Multiple instances of -L options can be specified.
OPERANDS
An operand is either in the form of a pathname or the form -l library.
At least one operand of the pathname form shall be specified. The
following operands shall be supported:
file.f The pathname of a FORTRAN source file to be compiled and
optionally passed to the link editor. The filename operand shall
be of this form if the -c option is used.
file.a A library of object files typically produced by ar, and passed
directly to the link editor. Implementations may recognize
implementation-defined suffixes other than .a as denoting object
file libraries.
file.o An object file produced by fort77 -c and passed directly to the
link editor. Implementations may recognize implementation-
defined suffixes other than .o as denoting object files.
The processing of other files is implementation-defined.
-l library
(The letter ell.) Search the library named:
liblibrary.a
A library is searched when its name is encountered, so the placement of
a -l operand is significant. Several standard libraries can be
specified in this manner, as described in the EXTENDED DESCRIPTION
section. Implementations may recognize implementation-defined suffixes
other than .a as denoting libraries.
STDIN
Not used.
INPUT FILES
The input file shall be one of the following: a text file containing
FORTRAN source code; an object file in the format produced by fort77
-c; or a library of object files, in the format produced by archiving
zero or more object files, using ar. Implementations may supply
additional utilities that produce files in these formats. Additional
input files are implementation-defined.
A <tab> encountered within the first six characters on a line of source
code shall cause the compiler to interpret the following character as
if it were the seventh character on the line (that is, in column 7).
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
fort77:
LANG Provide a default value for the internationalization variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables
used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all
the other internationalization variables.
LC_CTYPE
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input files).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
TMPDIR Determine the pathname that should override the default
directory for temporary files, if any.
ASYNCHRONOUS EVENTS
Default.
STDOUT
Not used.
STDERR
The standard error shall be used only for diagnostic messages. If more
than one file operand ending in .f (or possibly other unspecified
suffixes) is given, for each such file:
"%s:\n", <file>
may be written to allow identification of the diagnostic message with
the appropriate input file.
This utility may produce warning messages about certain conditions that
do not warrant returning an error (non-zero) exit value.
OUTPUT FILES
Object files, listing files, and executable files shall be produced in
unspecified formats.
EXTENDED DESCRIPTION
Standard Libraries
The fort77 utility shall recognize the following -l operand for the
standard library:
-l f This library contains all functions referenced in the
ANSI X3.9-1978 standard. This operand shall not be required to
be present to cause a search of this library.
In the absence of options that inhibit invocation of the link editor,
such as -c, the fort77 utility shall cause the equivalent of a -l f
operand to be passed to the link editor as the last -l operand, causing
it to be searched after all other object files and libraries are
loaded.
It is unspecified whether the library libf.a exists as a regular file.
The implementation may accept as -l operands names of objects that do
not exist as regular files.
External Symbols
The FORTRAN compiler and link editor shall support the significance of
external symbols up to a length of at least 31 bytes; case folding is
permitted. The action taken upon encountering symbols exceeding the
implementation-defined maximum symbol length is unspecified.
The compiler and link editor shall support a minimum of 511 external
symbols per source or object file, and a minimum of 4095 external
symbols total. A diagnostic message is written to standard output if
the implementation-defined limit is exceeded; other actions are
unspecified.
EXIT STATUS
The following exit values shall be returned:
0 Successful compilation or link edit.
>0 An error occurred.
CONSEQUENCES OF ERRORS
When fort77 encounters a compilation error, it shall write a diagnostic
to standard error and continue to compile other source code operands.
It shall return a non-zero exit status, but it is implementation-
defined whether an object module is created. If the link edit is
unsuccessful, a diagnostic message shall be written to standard error,
and fort77 shall exit with a non-zero status.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
The following usage example compiles xyz.f and creates the executable
file foo:
fort77 -o foo xyz.f
The following example compiles xyz.f and creates the object file xyz.o:
fort77 -c xyz.f
The following example compiles xyz.f and creates the executable file
a.out:
fort77 xyz.f
The following example compiles xyz.f, links it with b.o, and creates
the executable a.out:
fort77 xyz.f b.o
RATIONALE
The name of this utility was chosen as fort77 to parallel the renaming
of the C compiler. The name f77 was not chosen to avoid problems with
historical implementations. The ANSI X3.9-1978 standard was selected as
a normative reference because the ISO/IEC version of FORTRAN-77 has
been superseded by the ISO/IEC 1539:1990 standard (Fortran-90).
The file inclusion and symbol definition #define mechanisms used by the
c99 utility were not included in this volume of
IEEE Std 1003.1-2001-even though they are commonly implemented-since
there is no requirement that the FORTRAN compiler use the C
preprocessor.
The -onetrip option was not included in this volume of
IEEE Std 1003.1-2001, even though many historical compilers support it,
because it is derived from FORTRAN-66; it is an anachronism that should
not be perpetuated.
Some implementations produce compilation listings. This aspect of
FORTRAN has been left unspecified because there was controversy
concerning the various methods proposed for implementing it: a -V
option overlapped with historical vendor practice and a naming
convention of creating files with .l suffixes collided with historical
lex file naming practice.
There is no -I option in this version of this volume of
IEEE Std 1003.1-2001 to specify a directory for file inclusion. An
INCLUDE directive has been a part of the Fortran-90 discussions, but an
interface supporting that standard is not in the current scope.
It is noted that many FORTRAN compilers produce an object module even
when compilation errors occur; during a subsequent compilation, the
compiler may patch the object module rather than recompiling all the
code. Consequently, it is left to the implementor whether or not an
object file is created.
A reference to MIL-STD-1753 was removed from an early proposal in
response to a request from the POSIX FORTRAN-binding standard
developers. It was not the intention of the standard developers to
require certification of the FORTRAN compiler, and IEEE Std 1003.9-1992
does not specify the military standard or any special preprocessing
requirements. Furthermore, use of that document would have been
inappropriate for an international standard.
The specification of optimization has been subject to changes through
early proposals. At one time, -O and -N were Booleans: optimize and do
not optimize (with an unspecified default). Some historical practice
led this to be changed to:
-O 0 No optimization.
-O 1 Some level of optimization.
-O n Other, unspecified levels of optimization.
It is not always clear whether "good code generation" is the same thing
as optimization. Simple optimizations of local actions do not usually
affect the semantics of a program. The -O 0 option has been included to
accommodate the very particular nature of scientific calculations in a
highly optimized environment; compilers make errors. Some degree of
optimization is expected, even if it is not documented here, and the
ability to shut it off completely could be important when porting an
application. An implementation may treat -O 0 as "do less than normal"
if it wishes, but this is only meaningful if any of the operations it
performs can affect the semantics of a program. It is highly dependent
on the implementation whether doing less than normal is logical. It is
not the intent of the -O 0 option to ask for inefficient code
generation, but rather to assure that any semantically visible
optimization is suppressed.
The specification of standard library access is consistent with the C
compiler specification. Implementations are not required to have
/usr/lib/libf.a, as many historical implementations do, but if not they
are required to recognize f as a token.
External symbol size limits are in normative text; conforming
applications need to know these limits. However, the minimum maximum
symbol length should be taken as a constraint on a conforming
application, not on an implementation, and consequently the action
taken for a symbol exceeding the limit is unspecified. The minimum size
for the external symbol table was added for similar reasons.
The CONSEQUENCES OF ERRORS section clearly specifies the behavior of
the compiler when compilation or link-edit errors occur. The behavior
of several historical implementations was examined, and the choice was
made to be silent on the status of the executable, or a.out, file in
the face of compiler or linker errors. If a linker writes the
executable file, then links it on disk with lseek()s and write()s, the
partially linked executable file can be left on disk and its execute
bits turned off if the link edit fails. However, if the linker links
the image in memory before writing the file to disk, it need not touch
the executable file (if it already exists) because the link edit fails.
Since both approaches are historical practice, a conforming application
shall rely on the exit status of fort77, rather than on the existence
or mode of the executable file.
The -g and -s options are not specified as mutually-exclusive.
Historically these two options have been mutually-exclusive, but
because both are so loosely specified, it seemed appropriate to leave
their interaction unspecified.
The requirement that conforming applications specify compiler options
separately is to reserve the multi-character option name space for
vendor-specific compiler options, which are known to exist in many
historical implementations. Implementations are not required to
recognize, for example, -gc as if it were -g -c; nor are they forbidden
from doing so. The SYNOPSIS shows all of the options separately to
highlight this requirement on applications.
Echoing filenames to standard error is considered a diagnostic message
because it would otherwise be difficult to associate an error message
with the erring file. They are described with "may" to allow
implementations to use other methods of identifying files and to
parallel the description in c99.
FUTURE DIRECTIONS
A compilation system based on the ISO/IEC 1539:1990 standard
(Fortran-90) may be considered for a future version; it may have a
different utility name from fort77.
SEE ALSO
ar , asa , c99 , umask() , the System Interfaces volume of
IEEE Std 1003.1-2001, exec
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .