-@c Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+@c Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
@c Free Software Foundation, Inc.
@c This is part of the GNU Fortran manual.
@c For copying conditions, see the file gfortran.texi.
@c man begin DESCRIPTION
The @command{gfortran} command supports all the options supported by the
-@command{gcc} command. Only options specific to GNU Fortran are documented here.
+@command{gcc} command. Only options specific to GNU Fortran are documented
+here.
@xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
Collection (GCC)}, for information
@table @emph
@item Fortran Language Options
@xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
-@gccoptlist{-fall-intrinsics -ffree-form -fno-fixed-form @gol
--fdollar-ok -fimplicit-none -fmax-identifier-length @gol
--std=@var{std} -fd-lines-as-code -fd-lines-as-comments @gol
--ffixed-line-length-@var{n} -ffixed-line-length-none @gol
--ffree-line-length-@var{n} -ffree-line-length-none @gol
--fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
--fcray-pointer -fopenmp -fno-range-check -fbackslash -fmodule-private}
+@gccoptlist{-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code @gol
+-fd-lines-as-comments -fdefault-double-8 -fdefault-integer-8 @gol
+-fdefault-real-8 -fdollar-ok -ffixed-line-length-@var{n} @gol
+-ffixed-line-length-none -ffree-form -ffree-line-length-@var{n} @gol
+-ffree-line-length-none -fimplicit-none -finteger-4-integer-8 @gol
+-fmax-identifier-length -fmodule-private -fno-fixed-form -fno-range-check @gol
+-fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 @gol
+-freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=@var{std}
+}
@item Preprocessing Options
@xref{Preprocessing Options,,Enable and customize preprocessing}.
-@gccoptlist{-cpp -dD -dI -dM -dN -dU -fworking-directory @gol
--imultilib @var{dir} -iprefix @var{file} -isysroot @var{dir} @gol
--iquote -isystem @var{dir} -nocpp -nostdinc -undef @gol
--A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol
--C -CC -D@var{macro}@r{[}=@var{defn}@r{]} -U@var{macro} -H -P}
+@gccoptlist{-A-@var{question}@r{[}=@var{answer}@r{]}
+-A@var{question}=@var{answer} -C -CC -D@var{macro}@r{[}=@var{defn}@r{]}
+-H -P @gol
+-U@var{macro} -cpp -dD -dI -dM -dN -dU -fworking-directory
+-imultilib @var{dir} @gol
+-iprefix @var{file} -iquote -isysroot @var{dir} -isystem @var{dir} -nocpp
+-nostdinc @gol
+-undef
+}
@item Error and Warning Options
@xref{Error and Warning Options,,Options to request or suppress errors
and warnings}.
-@gccoptlist{-fmax-errors=@var{n}
--fsyntax-only -pedantic -pedantic-errors -Wall @gol
--Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol
--Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation @gol
--Wintrinsics-std -Wreal-q-constant -Wsurprising -Wno-tabs -Wunderflow @gol
--Wunused-parameter -Wintrinsic-shadow -Wno-align-commons @gol
--Wfunction-elimination}
+@gccoptlist{-Waliasing -Wall -Wampersand -Warray-bounds
+-Wcharacter-truncation @gol
+-Wconversion -Wfunction-elimination -Wimplicit-interface @gol
+-Wimplicit-procedure -Wintrinsic-shadow -Wintrinsics-std @gol
+-Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant @gol
+-Wsurprising -Wunderflow -Wunused-parameter -fmax-errors=@var{n}
+-fsyntax-only @gol
+-pedantic -pedantic-errors
+}
@item Debugging Options
@xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
-@gccoptlist{-fdump-fortran-original -fdump-fortran-optimized @gol
--ffpe-trap=@var{list} -fbacktrace -fdump-parse-tree}
+@gccoptlist{-fbacktrace -fdump-fortran-optimized -fdump-fortran-original @gol
+-fdump-parse-tree -ffpe-trap=@var{list}
+}
@item Directory Options
@xref{Directory Options,,Options for directory search}.
@item Runtime Options
@xref{Runtime Options,,Options for influencing runtime behavior}.
-@gccoptlist{-fconvert=@var{conversion} -fno-range-check
--frecord-marker=@var{length} @gol -fmax-subrecord-length=@var{length}
--fsign-zero}
+@gccoptlist{-fconvert=@var{conversion} -fmax-subrecord-length=@var{length}
+-fno-range-check @gol
+-frecord-marker=@var{length} -fsign-zero
+}
@item Code Generation Options
@xref{Code Gen Options,,Options for code generation conventions}.
-@gccoptlist{-fno-automatic -ff2c -fno-underscoring @gol
--fno-whole-file -fsecond-underscore @gol
--fbounds-check -fcheck-array-temporaries -fmax-array-constructor =@var{n} @gol
+@gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
+-fbounds-check -fcheck-array-temporaries @gol
-fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
--fcoarray=@var{<none|single|lib>} -fmax-stack-var-size=@var{n} @gol
--fstack-arrays @gol
--fpack-derived -frepack-arrays -fshort-enums -fexternal-blas @gol
--fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol
--finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
--finit-logical=@var{<true|false>} -finit-character=@var{n} @gol
--fno-align-commons -fno-protect-parens -frealloc-lhs @gol
--faggressive-function-elimination -ffrontend-optimize}
+-fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c
+-ffrontend-optimize @gol
+-finit-character=@var{n} -finit-integer=@var{n} -finit-local-zero @gol
+-finit-logical=@var{<true|false>}
+-finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
+-fmax-array-constructor=@var{n} -fmax-stack-var-size=@var{n}
+-fno-align-commons @gol
+-fno-automatic -fno-protect-parens -fno-underscoring -fno-whole-file @gol
+-fsecond-underscore -fpack-derived -frealloc-lhs -frecursive @gol
+-frepack-arrays -fshort-enums -fstack-arrays
+}
@end table
-@menu
-* Fortran Dialect Options:: Controlling the variant of Fortran language
- compiled.
-* Preprocessing Options:: Enable and customize preprocessing.
-* Error and Warning Options:: How picky should the compiler be?
-* Debugging Options:: Symbol tables, measurements, and debugging dumps.
-* Directory Options:: Where to find module files
-* Link Options :: Influencing the linking step
-* Runtime Options:: Influencing runtime behavior
-* Code Gen Options:: Specifying conventions for function calls, data layout
- and register usage.
-@end menu
-
@node Fortran Dialect Options
@section Options controlling Fortran dialect
@cindex dialect options
@code{IMPLICIT} statements. This is the equivalent of adding
@code{implicit none} to the start of every procedure.
+@item -finteger-4-integer-8
+@opindex @code{finteger-4-integer-8}
+Promote all @code{INTEGER(KIND=4)} entities to an @code{INTEGER(KIND=8)}
+entities. If @code{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 @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O. Inspection of the intermediate
+representation of the translated Fortran code, produced by
+@option{-fdump-tree-original}, is suggested.
+
@item -fcray-pointer
@opindex @code{fcray-pointer}
Enable the Cray pointer extension, which provides C-like pointer
on most systems, but with @option{-fno-range-check} the value will
``wrap around'' and @code{i} will be initialized to @math{-1} instead.
+@item -freal-4-real-8
+@itemx -freal-4-real-10
+@itemx -freal-8-real-4
+@itemx -freal-8-real-10
+@itemx -freal-8-real-16
+@opindex @code{freal-4-real-8}
+@opindex @code{freal-4-real-10}
+@opindex @code{freal-4-real-16}
+@opindex @code{freal-8-real-4}
+@opindex @code{freal-8-real-10}
+@opindex @code{freal-8-real-16}
+@cindex options, real kind type promotion
+Promote all @code{REAL(KIND=M)} entities to @code{REAL(KIND=N)} entities.
+If @code{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 @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O. Inspection of the intermediate
+representation of the translated Fortran code, produced by
+@option{-fdump-tree-original}, is suggested.
+
@item -std=@var{std}
@opindex @code{std=}@var{std} option
Specify the standard to which the program is expected to conform, which
preprocessing. When this option is enabled, the preprocessor will emit,
after the initial linemarker, a second linemarker with the current
working directory followed by two slashes. GCC will use this directory,
-when it's present in the preprocessed input, as the directory emitted
+when it is present in the preprocessed input, as the directory emitted
as the current working directory in some debugging information formats.
This option is implicitly enabled if debugging information is enabled,
but this can be inhibited with the negated form
@item -fsyntax-only
@opindex @code{fsyntax-only}
@cindex syntax checking
-Check the code for syntax errors, but don't actually compile it. This
+Check the code for syntax errors, but do not actually compile it. This
will generate module files for each module present in the code, but no
other output file.
@opindex @code{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 @code{SIGN} intrinsic. @code{fno-sign-zero} does not
-print the negative sign of zero values and regards zero as positive
-number in the @code{SIGN} intrinsic for compatibility with F77.
-Default behavior is to show the negative sign.
+negative in the @code{SIGN} intrinsic. @option{-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 @code{SIGN} intrinsic for
+compatibility with Fortran 77. The default is @option{-fsign-zero}.
@end table
@node Code Gen Options
@opindex @code{fstack-arrays}
Adding this option will make the fortran compiler put all local arrays,
even those of unknown size onto stack memory. If your program uses very
-large local arrays it's possible that you'll have to extend your runtime
+large local arrays it is possible that you will have to extend your runtime
limits for stack memory on some operating systems. This flag is enabled
by default at optimization level @option{-Ofast}.
the real and imaginary parts of local @code{COMPLEX} variables),
@option{-finit-logical=@var{<true|false>}}, and
@option{-finit-character=@var{n}} (where @var{n} is an ASCII character
-value) options. These options do not initialize components of derived
-type variables, nor do they initialize variables that appear in an
-@code{EQUIVALENCE} statement. (This limitation may be removed in
-future releases).
+value) options. These options do not initialize
+@itemize @bullet
+@item
+allocatable arrays
+@item
+components of derived type variables
+@item
+variables that appear in an @code{EQUIVALENCE} statement.
+@end itemize
+(These limitations may be removed in future releases).
Note that the @option{-finit-real=nan} option initializes @code{REAL}
and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN
optimizations may convert them into quiet NaN and that trapping
needs to be enabled (e.g. via @option{-ffpe-trap}).
+Finally, note that enabling any of the @option{-finit-*} options will
+silence warnings that would have been emitted by @option{-Wuninitialized}
+for the affected local variables.
+
@item -falign-commons
@opindex @code{falign-commons}
@cindex alignment of @code{COMMON} blocks
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