f2c (1) - Linux Manuals

f2c: Convert Fortran 77 to C or C++


f2c - Convert Fortran 77 to C or C++


f2c [ option ... ] file ...


F2c converts Fortran 77 source code in files with names ending in or to C (or C++) source files in the current directory, with substituted for the final or `.F'. If no Fortran files are named, f2c reads Fortran from standard input and writes C on standard output. File names that end with or are taken to be prototype files, as produced by option `-P', and are read first.

The following options have the same meaning as in f77(1).

Compile code to check that subscripts are within declared array bounds.
Render INTEGER and LOGICAL as short, INTEGER*4 as long int. Assume the default libF77 and libI77: allow only INTEGER*4 (and no LOGICAL) variables in INQUIREs. Option confirms the default rendering of INTEGER as long int.
Look for a non-absolute include file first in the directory of the current input file, then in directories specified by -I options (one directory per option). Options -I2 and -I4 have precedence, so, e.g., a directory named 2 should be specified by -I./2 .
Compile DO loops that are performed at least once if reached. (Fortran 77 DO loops are not performed at all if the upper limit is smaller than the lower limit.)
Honor the case of variable and external names. Fortran keywords must be in lower case.
Make the default type of a variable `undefined' rather than using the default Fortran rules.
Suppress all warning messages, or, if the option is `-w66', just Fortran 66 compatibility warnings.

The following options are peculiar to f2c.

Produce ANSI C (default, starting 20020621). For old-style C, use option -K.
Make local variables automatic rather than static unless they appear in a DATA, EQUIVALENCE, NAMELIST, or SAVE statement.
Output C++ code.
Include original Fortran source as comments.
Do not recognize cdabs, cdcos, cdexp, cdlog, cdsin, and cdsqrt as synonyms for the double complex intrinsics zabs, zcos, zexp, zlog, zsin, and zsqrt, respectively, nor dreal as a synonym for dble.
Write files in directory dir instead of the current directory.
Declare uninitialized COMMON to be Extern (overridably defined in as extern).
Place uninitialized COMMON blocks in separate files: COMMON /ABC/ appears in file abc_com.c. Option `-e1c' bundles the separate files into the output file, with comments that give an unbundling sed(1) script.
Complain about f77(1) extensions.
Assume free-format input: accept text after column 72 and do not pad fixed-format lines shorter than 72 characters with blanks.
Treat text appearing after column 72 as an error.
Include original Fortran line numbers in #line lines.
Emulate Fortran 66's treatment of Hollerith: try to align character strings on word (or, if the option is `-hd', on double-word) boundaries.
Similar to -I2, but assume a modified libF77 and libI77 (compiled with -Df2c_i2), so INTEGER and LOGICAL variables may be assigned by INQUIRE and array lengths are stored in short ints.
Do not recognize the Fortran 90 bit-manipulation intrinsics btest, iand, ibclr, ibits, ibset, ieor, ior, ishft, and ishftc.
Use temporary values to enforce Fortran expression evaluation where K&R (first edition) parenthesization rules allow rearrangement. If the option is `-krd', use double precision temporaries even for single-precision operands.
Write a file.P of ANSI (or C++) prototypes for definitions in each input file.f or file.F. When reading Fortran from standard input, write prototypes at the beginning of standard output. Option -Ps implies -P and gives exit status 4 if rerunning f2c may change prototypes or declarations.
Supply preprocessor definitions to make common-block members look like local variables.
Do not promote REAL functions and operations to DOUBLE PRECISION. Option confirms the default, which imitates f77.
Cast REAL arguments of intrinsic functions and values of REAL functions (including intrinsics) to REAL.
Preserve multidimensional subscripts. Suppressed by option .
Put temporary files in directory dir.
Dynamically initialize local variables, except those appearing in SAVE or DATA statements, with values that may help find references to uninitialized variables. For example, with IEEE arithmetic, initialize local floating-point variables to signaling NaNs.
Suppress warnings when COMMON or EQUIVALENCE forces odd-word alignment of doubles.
Assume n characters/word (default 4) when initializing numeric variables with character data.
Do not implicitly recognize DOUBLE COMPLEX.
Do not recognize backslash escapes (\", \', \0, \\, \b, \f, \n, \r, \t, \v) in character strings.
Inhibit C output, but produce -P output.
Reject include statements.
Disallow INTEGER*8 , or, if the option is `-!i8const', permit INTEGER*8 but do not promote integer constants to INTEGER*8 when they involve more than 32 bits.
Don't infer types of untyped EXTERNAL procedures from use as parameters to previously defined or prototyped procedures.
Do not attempt to infer ANSI or C++ prototypes from usage.

The resulting C invokes the support routines of f77; object code should be loaded by f77 or with ld(1) or cc(1) options -lF77 -lI77 -lm. Calling conventions are those of f77: see the reference below.


file.[fF] input file
output file
header file
intrinsic function library
Fortran I/O library
C library, see section 3


The diagnostics produced by f2c are intended to be self-explanatory.


Floating-point constant expressions are simplified in the floating-point arithmetic of the machine running f2c, so they are typically accurate to at most 16 or 17 decimal places.
Untypable EXTERNAL functions are declared int.
There is no notation for INTEGER*8 constants.
Some intrinsic functions do not yet work with INTEGER*8 .


S. I. Feldman and P. J. Weinberger, `A Portable Fortran 77 Compiler', UNIX Time Sharing System Programmer's Manual, Tenth Edition, Volume 2, AT&T Bell Laboratories, 1990.