The following options control the details of the Fortran dialect accepted by the compiler:
-ffree-form
-ffixed-form
-fall-intrinsics
-std=f95
to force standard-compliance but get access to the full range of intrinsics available with gfortran
. As a consequence, -Wintrinsics-std
will be ignored and no user-defined procedure with the same name as any intrinsic will be called except when it is explicitly declared EXTERNAL
. -fd-lines-as-code
-fd-lines-as-comments
d
or D
in fixed form sources. If the -fd-lines-as-code
option is given they are treated as if the first column contained a blank. If the -fd-lines-as-comments
option is given, they are treated as comment lines. -fdollar-ok
$
’ as a valid non-first character in a symbol name. Symbols that start with ‘$
’ are rejected since it is unclear which rules to apply to implicit typing as different vendors implement different rules. Using ‘$
’ in IMPLICIT
statements is also rejected. -fbackslash
\a
, \b
, \f
, \n
, \r
, \t
, \v
, \\
, and \0
to the ASCII characters alert, backspace, form feed, newline, carriage return, horizontal tab, vertical tab, backslash, and NUL, respectively. Additionally, \x
nn, \u
nnnn and \U
nnnnnnnn (where each n is a hexadecimal digit) are translated into the Unicode characters corresponding to the specified code points. All other combinations of a character preceded by \ are unexpanded. -fmodule-private
PRIVATE
. Use-associated entities will not be accessible unless they are explicitly declared as PUBLIC
. -ffixed-line-length-
n
Popular values for n include 72 (the standard and the default), 80 (card image), and 132 (corresponding to “extended-source” options in some popular compilers). n may also be ‘none
’, meaning that the entire line is meaningful and that continued character constants never have implicit spaces appended to them to fill out the line. -ffixed-line-length-0
means the same thing as -ffixed-line-length-none
.
-ffree-line-length-
n
none
’, meaning that the entire line is meaningful. -ffree-line-length-0
means the same thing as -ffree-line-length-none
. -fmax-identifier-length=
n
-fimplicit-none
IMPLICIT
statements. This is the equivalent of adding implicit none
to the start of every procedure. -fcray-pointer
-fopenacc
!$acc
directives in free form and c$acc
, *$acc
and !$acc
directives in fixed form, !$
conditional compilation sentinels in free form and c$
, *$
and !$
sentinels in fixed form, and when linking arranges for the OpenACC runtime library to be linked in. Note that this is an experimental feature, incomplete, and subject to change in future versions of GCC. See https://gcc.gnu.org/wiki/OpenACC for more information.
-fopenmp
!$omp
directives in free form and c$omp
, *$omp
and !$omp
directives in fixed form, !$
conditional compilation sentinels in free form and c$
, *$
and !$
sentinels in fixed form, and when linking arranges for the OpenMP runtime library to be linked in. The option -fopenmp
implies -frecursive
. -fno-range-check
a = 1. / 0
. With this option, no error will be given and a
will be assigned the value +Infinity
. If an expression evaluates to a value outside of the relevant range of [-HUGE()
:HUGE()
], then the expression will be replaced by -Inf
or +Inf
as appropriate. Similarly, DATA i/Z'FFFFFFFF'/
will result in an integer overflow on most systems, but with -fno-range-check
the value will “wrap around” and i
will be initialized to -1 instead. -fdefault-integer-8
42
. Unlike -finteger-4-integer-8
, it does not promote variables with explicit kind declaration. -fdefault-real-8
1.0
, and does promote the default width of DOUBLE PRECISION
to 16 bytes if possible, unless -fdefault-double-8
is given, too. Unlike -freal-4-real-8
, it does not promote variables with explicit kind declaration. -fdefault-double-8
DOUBLE PRECISION
type to an 8 byte wide type. Do nothing if this is already the default. If -fdefault-real-8
is given, DOUBLE PRECISION
would instead be promoted to 16 bytes if possible, and -fdefault-double-8
can be used to prevent this. The kind of real constants like 1.d0
will not be changed by -fdefault-real-8
though, so also -fdefault-double-8
does not affect it. -finteger-4-integer-8
INTEGER(KIND=4)
entities to an INTEGER(KIND=8)
entities. If KIND=8
is unavailable, then an error will be issued. This option should be used with care and may not be suitable for your codes. Areas of possible concern include calls to external procedures, alignment in EQUIVALENCE
and/or COMMON
, generic interfaces, BOZ literal constant conversion, and I/O. Inspection of the intermediate representation of the translated Fortran code, produced by -fdump-tree-original
, is suggested. -freal-4-real-8
-freal-4-real-10
-freal-4-real-16
-freal-8-real-4
-freal-8-real-10
-freal-8-real-16
REAL(KIND=M)
entities to REAL(KIND=N)
entities. If REAL(KIND=N)
is unavailable, then an error will be issued. All other real kind types are unaffected by this option. These options should be used with care and may not be suitable for your codes. Areas of possible concern include calls to external procedures, alignment in EQUIVALENCE
and/or COMMON
, generic interfaces, BOZ literal constant conversion, and I/O. Inspection of the intermediate representation of the translated Fortran code, produced by -fdump-tree-original
, is suggested. -std=
std
f95
’, ‘f2003
’, ‘f2008
’, ‘gnu
’, or ‘legacy
’. The default value for std is ‘gnu
’, which specifies a superset of the Fortran 95 standard that includes all of the extensions supported by GNU Fortran, although warnings will be given for obsolete extensions not recommended for use in new code. The ‘legacy
’ value is equivalent but without the warnings for obsolete extensions, and may be useful for old non-standard programs. The ‘f95
’, ‘f2003
’ and ‘f2008
’ values specify strict conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards, respectively; errors are given for all extensions beyond the relevant language standard, and warnings are given for the Fortran 77 features that are permitted but obsolescent in later standards. ‘-std=f2008ts
’ allows the Fortran 2008 standard including the additions of the Technical Specification (TS) 29113 on Further Interoperability of Fortran with C and TS 18508 on Additional Parallel Features in Fortran.
© Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc-5.4.0/gfortran/Fortran-Dialect-Options.html