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       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 .