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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
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 POSIX.1‐2017, 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 POSIX.1‐2017, 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 POSIX.1‐2017 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 POSIX.1‐2017, 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 1539:1991 standard.
The file inclusion and symbol definition #define mechanisms used by the c99 utility were not included in
this volume of POSIX.1‐2017—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 POSIX.1‐2017, 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 POSIX.1‐2017 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
Future versions of this standard may withdraw this utility. There are implementations of compilers that
conform to much more recent versions of the FORTRAN programming language. Since there is no active
FORTRAN binding to POSIX.1‐2008, this standard does not need to specify any compiler.
SEE ALSO
ar, asa, c99, umask
The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines
The System Interfaces volume of POSIX.1‐2017, exec
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 FORT77(1POSIX)