@item Error and Warning Options
@xref{Error and Warning Options,,Options to request or suppress errors
and warnings}.
-@gccoptlist{-fmax-errors=@var{n} @gol
--fsyntax-only -pedantic -pedantic-errors @gol
--Wall -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol
--Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation @gol
--Wintrinsics-std -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter @gol
--Wintrinsic-shadow -Wno-align-commons -Wfunction-elimination}
+@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}
@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} -fdump-core -fbacktrace -fdump-parse-tree}
+-ffpe-trap=@var{list} -fbacktrace -fdump-parse-tree}
@item Directory Options
@xref{Directory Options,,Options for directory search}.
@item Code Generation Options
@xref{Code Gen Options,,Options for code generation conventions}.
@gccoptlist{-fno-automatic -ff2c -fno-underscoring @gol
--fwhole-file -fsecond-underscore @gol
+-fno-whole-file -fsecond-underscore @gol
-fbounds-check -fcheck-array-temporaries -fmax-array-constructor =@var{n} @gol
-fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
-fcoarray=@var{<none|single|lib>} -fmax-stack-var-size=@var{n} @gol
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.
+that are permitted but obsolescent in later standards. @samp{-std=f2008ts}
+allows the Fortran 2008 standard including the additions of the
+Technical Specification (TS) 29113 on Further Interoperability of Fortran
+with C.
@end table
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.
This currently includes @option{-Waliasing}, @option{-Wampersand},
@option{-Wconversion}, @option{-Wsurprising}, @option{-Wintrinsics-std},
@option{-Wno-tabs}, @option{-Wintrinsic-shadow}, @option{-Wline-truncation},
-and @option{-Wunused}.
+@option{-Wreal-q-constant} and @option{-Wunused}.
@item -Waliasing
@opindex @code{Waliasing}
be used to never trigger this behavior and always link to the intrinsic
regardless of the selected standard.
+@item -Wreal-q-constant
+@opindex @code{Wreal-q-constant}
+@cindex warnings, @code{q} exponent-letter
+Produce a warning if a real-literal-constant contains a @code{q}
+exponent-letter.
+
@item -Wsurprising
@opindex @code{Wsurprising}
@cindex warnings, suspicious code
@item -ffpe-trap=@var{list}
@opindex @code{ffpe-trap=}@var{list}
-Specify a list of IEEE exceptions when a Floating Point Exception
-(FPE) should be raised. On most systems, this will result in a SIGFPE
-signal being sent and the program being interrupted, producing a core
-file useful for debugging. @var{list} is a (possibly empty) comma-separated
-list of the following IEEE exceptions: @samp{invalid} (invalid floating
-point operation, such as @code{SQRT(-1.0)}), @samp{zero} (division by
-zero), @samp{overflow} (overflow in a floating point operation),
-@samp{underflow} (underflow in a floating point operation),
-@samp{precision} (loss of precision during operation) and @samp{denormal}
-(operation produced a denormal value).
-
-Some of the routines in the Fortran runtime library, like
-@samp{CPU_TIME}, are likely to trigger floating point exceptions when
-@code{ffpe-trap=precision} is used. For this reason, the use of
-@code{ffpe-trap=precision} is not recommended.
-
-@item -fbacktrace
-@opindex @code{fbacktrace}
+Specify a list of floating point exception traps to enable. On most
+systems, if a floating point exception occurs and the trap for that
+exception is enabled, a SIGFPE signal will be sent and the program
+being aborted, producing a core file useful for debugging. @var{list}
+is a (possibly empty) comma-separated list of the following
+exceptions: @samp{invalid} (invalid floating point operation, such as
+@code{SQRT(-1.0)}), @samp{zero} (division by zero), @samp{overflow}
+(overflow in a floating point operation), @samp{underflow} (underflow
+in a floating point operation), @samp{inexact} (loss of precision
+during operation), and @samp{denormal} (operation performed on a
+denormal value). The first five exceptions correspond to the five
+IEEE 754 exceptions, whereas the last one (@samp{denormal}) is not
+part of the IEEE 754 standard but is available on some common
+architectures such as x86.
+
+The first three exceptions (@samp{invalid}, @samp{zero}, and
+@samp{overflow}) often indicate serious errors, and unless the program
+has provisions for dealing with these exceptions, enabling traps for
+these three exceptions is probably a good idea.
+
+Many, if not most, floating point operations incur loss of precision
+due to rounding, and hence the @code{ffpe-trap=inexact} is likely to
+be uninteresting in practice.
+
+By default no exception traps are enabled.
+
+@item -fno-backtrace
+@opindex @code{fno-backtrace}
@cindex backtrace
@cindex trace
-Specify that, when a runtime error is encountered or a deadly signal is
-emitted (segmentation fault, illegal instruction, bus error or
-floating-point exception), the Fortran runtime
-library should output a backtrace of the error. This option
-only has influence for compilation of the Fortran main program.
-
-@item -fdump-core
-@cindex core, dump
-@opindex @code{fdump-core}
-Request that a core-dump file is written to disk when a runtime error
-is encountered on systems that support core dumps. This option is
-only effective for the compilation of the Fortran main program.
+When a serious runtime error is encountered or a deadly signal is
+emitted (segmentation fault, illegal instruction, bus error,
+floating-point exception, and the other POSIX signals that have the
+action @samp{core}), the Fortran runtime library tries to output a
+backtrace of the error. @code{-fno-backtrace} disables the backtrace
+generation. This option only has influence for compilation of the
+Fortran main program.
+
@end table
@xref{Debugging Options,,Options for Debugging Your Program or GCC,
@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
prevent accidental linking between procedures with incompatible
interfaces.
-@item -fwhole-file
-@opindex @code{fwhole-file}
-By default, GNU Fortran parses, resolves and translates each procedure
-in a file separately. Using this option modifies this such that the
-whole file is parsed and placed in a single front-end tree. During
-resolution, in addition to all the usual checks and fixups, references
+@item -fno-whole-file
+@opindex @code{fno-whole-file}
+This flag causes the compiler to resolve and translate each procedure in
+a file separately.
+
+By default, the whole file is parsed and placed in a single front-end tree.
+During resolution, in addition to all the usual checks and fixups, references
to external procedures that are in the same file effect resolution of
-that procedure, if not already done, and a check of the interfaces. The
+that procedure, if not already done, and a check of the interfaces. The
dependences are resolved by changing the order in which the file is
translated into the backend tree. Thus, a procedure that is referenced
is translated before the reference and the duplication of backend tree
declarations eliminated.
+The @option{-fno-whole-file} option is deprecated and may lead to wrong code.
+
@item -fsecond-underscore
@opindex @code{fsecond-underscore}
@cindex underscore
@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
-limits for stack memory on some operating systems.
+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}.
+
@item -fpack-derived
@opindex @code{fpack-derived}
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
@option{-fno-protect-parens} allows the compiler to reorder @code{REAL} and
@code{COMPLEX} expressions to produce faster code. Note that for the re-association
optimization @option{-fno-signed-zeros} and @option{-fno-trapping-math}
-need to be in effect.
+need to be in effect. The parentheses protection is enabled by default, unless
+@option{-Ofast} is given.
@item -frealloc-lhs
@opindex @code{frealloc-lhs}
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