2.8 Influencing runtime behavior

These options affect the runtime behavior of programs compiled with GNU Fortran.

-fconvert=conversion

Specify the representation of data for unformatted files. Valid values for conversion on most systems are: `native', the default; `swap', swap between big- and little-endian; `big-endian', use big-endian representation for unformatted files; `little-endian', use little-endian representation for unformatted files.

On POWER systems which suppport -mabi=ieeelongdouble, there are additional options, which can be combined with others with commas. Those are

• -fconvert=r16_ieee Use IEEE 128-bit format for REAL(KIND=16).
• -fconvert=r16_ibm Use IBM long double format for REAL(KIND=16).

This option has an effect only when used in the main program. The CONVERT specifier and the GFORTRAN_CONVERT_UNIT environment variable override the default specified by -fconvert.

-frecord-marker=length

Specify the length of record markers for unformatted files. Valid values for length are 4 and 8. Default is 4. This is different from previous versions of gfortran, which specified a default record marker length of 8 on most systems. If you want to read or write files compatible with earlier versions of gfortran, use -frecord-marker=8.

-fmax-subrecord-length=length

Specify the maximum length for a subrecord. The maximum permitted value for length is 2147483639, which is also the default. Only really useful for use by the gfortran testsuite.

-fsign-zero

When enabled, floating point numbers of value zero with the sign bit set are written as negative number in formatted output and treated as negative in the SIGN intrinsic. -fno-sign-zero does not print the negative sign of zero values (or values rounded to zero for I/O) and regards zero as positive number in the SIGN intrinsic for compatibility with Fortran 77. The default is -fsign-zero.