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/GNU Fortran 7

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 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.

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.

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https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gfortran/Runtime-Options.html