--- a/gcc/fortran/invoke.texi	Thu Oct 25 07:37:49 2018 +0900
+++ b/gcc/fortran/invoke.texi	Thu Feb 13 11:34:05 2020 +0900
@@ -1,10 +1,10 @@
-@c Copyright (C) 2004-2018 Free Software Foundation, Inc.
+@c Copyright (C) 2004-2020 Free Software Foundation, Inc.
 @c This is part of the GNU Fortran manual.   
 @c For copying conditions, see the file gfortran.texi.
 
 @ignore
 @c man begin COPYRIGHT
-Copyright @copyright{} 2004-2018 Free Software Foundation, Inc.
+Copyright @copyright{} 2004-2020 Free Software Foundation, Inc.
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -116,17 +116,18 @@
 @table @emph
 @item Fortran Language Options
 @xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
-@gccoptlist{-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code @gol
--fd-lines-as-comments @gol
--fdec -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math @gol
--fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
--fdefault-real-10 -fdefault-real-16 -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 -ffixed-form -fno-range-check @gol
--fopenacc -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}
--ftest-forall-temp
+@gccoptlist{-fall-intrinsics -fallow-argument-mismatch -fallow-invalid-boz @gol
+-fbackslash -fcray-pointer -fd-lines-as-code -fd-lines-as-comments @gol
+-fdec -fdec-char-conversions -fdec-structure -fdec-intrinsic-ints @gol
+-fdec-static -fdec-math -fdec-include -fdec-format-defaults @gol
+-fdec-blank-format-item -fdefault-double-8 -fdefault-integer-8 @gol
+-fdefault-real-8 -fdefault-real-10 -fdefault-real-16 -fdollar-ok @gol
+-ffixed-line-length-@var{n} -ffixed-line-length-none -fpad-source @gol
+-ffree-form -ffree-line-length-@var{n} -ffree-line-length-none @gol
+-fimplicit-none -finteger-4-integer-8 -fmax-identifier-length @gol
+-fmodule-private -ffixed-form -fno-range-check -fopenacc -fopenmp @gol
+-freal-4-real-10 -freal-4-real-16 -freal-4-real-8 -freal-8-real-10 @gol
+-freal-8-real-16 -freal-8-real-4 -std=@var{std} -ftest-forall-temp
 }
 
 @item Preprocessing Options
@@ -144,20 +145,23 @@
 @item Error and Warning Options
 @xref{Error and Warning Options,,Options to request or suppress errors
 and warnings}.
-@gccoptlist{-Waliasing -Wall -Wampersand -Wargument-mismatch -Warray-bounds
+@gccoptlist{-Waliasing -Wall -Wampersand -Warray-bounds @gol
 -Wc-binding-type -Wcharacter-truncation -Wconversion @gol
 -Wdo-subscript -Wfunction-elimination -Wimplicit-interface @gol
--Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only -Wintrinsics-std @gol
--Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant @gol
--Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs @gol
--Wrealloc-lhs-all -Wfrontend-loop-interchange -Wtarget-lifetime @gol
--fmax-errors=@var{n} -fsyntax-only -pedantic -pedantic-errors @gol
+-Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only @gol
+-Wintrinsics-std -Wline-truncation -Wno-align-commons @gol
+-Wno-overwrite-recursive -Wno-tabs -Wreal-q-constant -Wsurprising @gol
+-Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all @gol
+-Wfrontend-loop-interchange -Wtarget-lifetime -fmax-errors=@var{n} @gol
+-fsyntax-only -pedantic @gol
+-pedantic-errors @gol
 }
 
 @item Debugging Options
 @xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
 @gccoptlist{-fbacktrace -fdump-fortran-optimized -fdump-fortran-original @gol
--fdump-parse-tree -ffpe-trap=@var{list} -ffpe-summary=@var{list}
+-fdump-fortran-global -fdump-parse-tree -ffpe-trap=@var{list} @gol
+-ffpe-summary=@var{list}
 }
 
 @item Directory Options
@@ -176,26 +180,25 @@
 
 @item Interoperability Options
 @xref{Interoperability Options,,Options for interoperability}.
-@gccoptlist{-fc-prototypes}
+@gccoptlist{-fc-prototypes -fc-prototypes-external}
 
 @item Code Generation Options
 @xref{Code Gen Options,,Options for code generation conventions}.
 @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>} -fexternal-blas -ff2c
--ffrontend-loop-interchange @gol
--ffrontend-optimize @gol
+-fbounds-check -ftail-call-workaround -ftail-call-workaround=@var{n} @gol
+-fcheck-array-temporaries @gol
+-fcheck=@var{<all|array-temps|bits|bounds|do|mem|pointer|recursion>} @gol
+-fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c @gol
+-ffrontend-loop-interchange -ffrontend-optimize @gol
 -finit-character=@var{n} -finit-integer=@var{n} -finit-local-zero @gol
--finit-derived @gol
--finit-logical=@var{<true|false>}
--finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
+-finit-derived -finit-logical=@var{<true|false>} @gol
+-finit-real=@var{<zero|inf|-inf|nan|snan>}
 -finline-matmul-limit=@var{n} @gol
--fmax-array-constructor=@var{n} -fmax-stack-var-size=@var{n}
--fno-align-commons @gol
--fno-automatic -fno-protect-parens -fno-underscoring @gol
--fsecond-underscore -fpack-derived -frealloc-lhs -frecursive @gol
--frepack-arrays -fshort-enums -fstack-arrays
+-finline-arg-packing -fmax-array-constructor=@var{n} @gol
+-fmax-stack-var-size=@var{n} -fno-align-commons -fno-automatic @gol
+-fno-protect-parens -fno-underscoring -fsecond-underscore @gol
+-fpack-derived -frealloc-lhs -frecursive -frepack-arrays @gol
+-fshort-enums -fstack-arrays
 }
 @end table
 
@@ -230,6 +233,28 @@
 will be ignored and no user-defined procedure with the same name as any
 intrinsic will be called except when it is explicitly declared @code{EXTERNAL}.
 
+@item -fallow-argument-mismatch
+@opindex @code{fallow-argument-mismatch}
+Some code contains calls to external procedures whith mismatches
+between the calls and the procedure definition, or with mismatches
+between different calls. Such code is non-conforming, and will usually
+be flagged wi1th an error.  This options degrades the error to a
+warning, which can only be disabled by disabling all warnings vial
+@option{-w}.  Only a single occurrence per argument is flagged by this
+warning.  @option{-fallow-argument-mismatch} is implied by
+@option{-std=legacy}.
+
+Using this option is @emph{strongly} discouraged.  It is possible to
+provide standard-conforming code which allows different types of
+arguments by using an explicit interface and @code{TYPE(*)}.
+
+@item -fallow-invalid-boz
+@opindex @code{allow-invalid-boz}
+A BOZ literal constant can occur in a limited number of contexts in
+standard conforming Fortran.  This option degrades an error condition
+to a warning, and allows a BOZ literal constant to appear where the
+Fortran standard would otherwise prohibit its use.
+
 @item -fd-lines-as-code
 @itemx -fd-lines-as-comments
 @opindex @code{fd-lines-as-code}
@@ -249,12 +274,19 @@
 full documentation.
 
 Other flags enabled by this switch are:
-@option{-fdollar-ok} @option{-fcray-pointer} @option{-fdec-structure}
-@option{-fdec-intrinsic-ints} @option{-fdec-static} @option{-fdec-math}
+@option{-fdollar-ok} @option{-fcray-pointer} @option{-fdec-char-conversions}
+@option{-fdec-structure} @option{-fdec-intrinsic-ints} @option{-fdec-static}
+@option{-fdec-math} @option{-fdec-include} @option{-fdec-blank-format-item}
+@option{-fdec-format-defaults}
 
 If @option{-fd-lines-as-code}/@option{-fd-lines-as-comments} are unset, then
 @option{-fdec} also sets @option{-fd-lines-as-comments}.
 
+@item -fdec-char-conversions
+@opindex @code{fdec-char-conversions}
+Enable the use of character literals in assignments and @code{DATA} statements
+for non-character variables.
+
 @item -fdec-structure
 @opindex @code{fdec-structure}
 Enable DEC @code{STRUCTURE} and @code{RECORD} as well as @code{UNION},
@@ -277,6 +309,22 @@
 Enable DEC-style STATIC and AUTOMATIC attributes to explicitly specify
 the storage of variables and other objects.
 
+@item -fdec-include
+@opindex @code{fdec-include}
+Enable parsing of INCLUDE as a statement in addition to parsing it as
+INCLUDE line.  When parsed as INCLUDE statement, INCLUDE does not have to
+be on a single line and can use line continuations.
+
+@item -fdec-format-defaults
+@opindex @code{fdec-format-defaults}
+Enable format specifiers F, G and I to be used without width specifiers,
+default widths will be used instead.
+
+@item -fdec-blank-format-item
+@opindex @code{fdec-blank-format-item}
+Enable a blank format item at the end of a format specification i.e. nothing
+following the final comma.
+
 @item -fdollar-ok
 @opindex @code{fdollar-ok}
 @cindex @code{$}
@@ -315,8 +363,9 @@
 @opindex @code{ffixed-line-length-}@var{n}
 @cindex file format, fixed
 Set column after which characters are ignored in typical fixed-form
-lines in the source file, and through which spaces are assumed (as
-if padded to that length) after the ends of short fixed-form lines.
+lines in the source file, and, unless @code{-fno-pad-source}, through which
+spaces are assumed (as if padded to that length) after the ends of short
+fixed-form lines.
 
 Popular values for @var{n} include 72 (the
 standard and the default), 80 (card image), and 132 (corresponding
@@ -327,6 +376,15 @@
 @option{-ffixed-line-length-0} means the same thing as
 @option{-ffixed-line-length-none}.
 
+@item -fno-pad-source
+@opindex @code{fpad-source}
+By default fixed-form lines have spaces assumed (as if padded to that length)
+after the ends of short fixed-form lines.  This is not done either if
+@option{-ffixed-line-length-0}, @option{-ffixed-line-length-none} or
+if @option{-fno-pad-source} option is used.  With any of those options
+continued character constants never have implicit spaces appended
+to them to fill out the line.
+
 @item -ffree-line-length-@var{n}
 @opindex @code{ffree-line-length-}@var{n}
 @cindex file format, free
@@ -362,10 +420,6 @@
 @code{!$} 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
-@w{@uref{https://gcc.gnu.org/wiki/OpenACC}} for more information.
-
 @item -fopenmp
 @opindex @code{fopenmp}
 @cindex OpenMP
@@ -400,36 +454,45 @@
 
 @item -fdefault-real-8
 @opindex @code{fdefault-real-8}
-Set the default real type to an 8 byte wide type. This option also affects
-the kind of non-double real constants like @code{1.0}, and does promote
-the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
-@code{-fdefault-double-8} is given, too. Unlike @option{-freal-4-real-8},
-it does not promote variables with explicit kind declaration.
+Set the default real type to an 8 byte wide type.  This option also affects
+the kind of non-double real constants like @code{1.0}.  This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible.  If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-8}, @code{DOUBLE PRECISION}
+and double real constants are not promoted.  Unlike @option{-freal-4-real-8},
+@code{fdefault-real-8} does not promote variables with explicit kind
+declarations.
 
 @item -fdefault-real-10
 @opindex @code{fdefault-real-10}
-Set the default real type to a 10 byte wide type. This option also affects
-the kind of non-double real constants like @code{1.0}, and does promote
-the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
-@code{-fdefault-double-8} is given. Unlike @option{-freal-4-real-10},
-it does not promote variables with explicit kind declaration.
+Set the default real type to an 10 byte wide type.  This option also affects
+the kind of non-double real constants like @code{1.0}.  This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible.  If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-10}, @code{DOUBLE PRECISION}
+and double real constants are not promoted.  Unlike @option{-freal-4-real-10},
+@code{fdefault-real-10} does not promote variables with explicit kind
+declarations.
 
 @item -fdefault-real-16
 @opindex @code{fdefault-real-16}
-Set the default real type to a 16 byte wide type. This option also affects
-the kind of non-double real constants like @code{1.0}, and does promote
-the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
-@code{-fdefault-double-8} is given. Unlike @option{-freal-4-real-16},
-it does not promote variables with explicit kind declaration.
+Set the default real type to an 16 byte wide type.  This option also affects
+the kind of non-double real constants like @code{1.0}.  This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible.  If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-16}, @code{DOUBLE PRECISION}
+and double real constants are not promoted.  Unlike @option{-freal-4-real-16},
+@code{fdefault-real-16} does not promote variables with explicit kind
+declarations.
 
 @item -fdefault-double-8
 @opindex @code{fdefault-double-8}
-Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.  Do nothing if this
-is already the default.  If @option{-fdefault-real-8} is given,
-@code{DOUBLE PRECISION} would instead be promoted to 16 bytes if possible, and
-@option{-fdefault-double-8} can be used to prevent this.  The kind of real
-constants like @code{1.d0} will not be changed by @option{-fdefault-real-8}
-though, so also @option{-fdefault-double-8} does not affect it.
+Set the @code{DOUBLE PRECISION} type and double real constants
+like @code{1.d0} to an 8 byte wide type.  Do nothing if this
+is already the default.  This option prevents @option{-fdefault-real-8},
+@option{-fdefault-real-10}, and @option{-fdefault-real-16},
+from promoting @code{DOUBLE PRECISION} and double real constants like
+@code{1.d0} to 16 bytes.
 
 @item -finteger-4-integer-8
 @opindex @code{finteger-4-integer-8}
@@ -854,15 +917,6 @@
 non-comment, non-whitespace character after the ampersand that
 initiated the continuation.
 
-@item -Wargument-mismatch
-@opindex @code{Wargument-mismatch}
-@cindex warnings, argument mismatch
-@cindex warnings, parameter mismatch
-@cindex warnings, interface mismatch
-Warn about type, rank, and other mismatches between formal parameters and actual
-arguments to functions and subroutines.  These warnings are recommended and
-thus enabled by default.
-
 @item -Warray-temporaries
 @opindex @code{Warray-temporaries}
 @cindex warnings, array temporaries
@@ -918,8 +972,8 @@
 @opindex @code{Wfrontend-loop-interchange}
 @cindex warnings, loop interchange
 @cindex loop interchange, warning
-Enable warning for loop interchanges performed by the
-@option{-ffrontend-loop-interchange} option.
+Warn when using @option{-ffrontend-loop-interchange} for performing loop
+interchanges.
 
 @item -Wimplicit-interface
 @opindex @code{Wimplicit-interface}
@@ -938,7 +992,7 @@
 @opindex @code{Winteger-division}
 @cindex warnings, integer division
 @cindex warnings, division of integers
-Warn if a constant integer division truncates it result.
+Warn if a constant integer division truncates its result.
 As an example, 3/5 evaluates to 0.
 
 @item -Wintrinsics-std
@@ -951,6 +1005,15 @@
 be used to never trigger this behavior and always link to the intrinsic
 regardless of the selected standard.
 
+@item -Wno-overwrite-recursive
+@opindex @code{Woverwrite-recursive}
+@cindex  warnings, overwrite recursive
+Do not warn when @option{-fno-automatic} is used with @option{-frecursive}. Recursion
+will be broken if the relevant local variables do not have the attribute
+@code{AUTOMATIC} explicitly declared. This option can be used to suppress the warning
+when it is known that recursion is not broken. Useful for build environments that use
+@option{-Werror}.
+
 @item -Wreal-q-constant
 @opindex @code{Wreal-q-constant}
 @cindex warnings, @code{q} exponent-letter
@@ -1096,7 +1159,7 @@
 @item -Wdo-subscript
 @opindex @code{Wdo-subscript}
 Warn if an array subscript inside a DO loop could lead to an
-out-of-bounds access even if the compiler can not prove that the
+out-of-bounds access even if the compiler cannot prove that the
 statement is actually executed, in cases like
 @smallexample
   real a(3)
@@ -1156,6 +1219,14 @@
 compiler errors for features which have only recently been added. This
 option is deprecated; use @code{-fdump-fortran-original} instead.
 
+@item -fdump-fortran-global
+@opindex @code{fdump-fortran-global}
+Output a list of the global identifiers after translating into
+middle-end representation. Mostly useful for debugging the GNU Fortran
+compiler itself. The output generated by this option might change
+between releases.  This option may also generate internal compiler
+errors for features which have only recently been added.
+
 @item -ffpe-trap=@var{list}
 @opindex @code{ffpe-trap=}@var{list}
 Specify a list of floating point exception traps to enable.  On most
@@ -1178,6 +1249,12 @@
 has provisions for dealing with these exceptions, enabling traps for
 these three exceptions is probably a good idea.
 
+If the option is used more than once in the command line, the lists will
+be joined: '@code{ffpe-trap=}@var{list1} @code{ffpe-trap=}@var{list2}'
+is equivalent to @code{ffpe-trap=}@var{list1},@var{list2}.
+
+Note that once enabled an exception cannot be disabled (no negative form).
+
 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.
@@ -1193,6 +1270,9 @@
 @samp{underflow}, @samp{inexact} and @samp{denormal}. (See
 @option{-ffpe-trap} for a description of the exceptions.)
 
+If the option is used more than once in the command line, only the
+last one will be used.
+
 By default, a summary for all exceptions but @samp{inexact} is shown.
 
 @item -fno-backtrace
@@ -1361,6 +1441,9 @@
 variables smaller than the value given by @option{-fmax-stack-var-size}.
 Use the option @option{-frecursive} to use no static memory. 
 
+Local variables or arrays having an explicit @code{SAVE} attribute are
+silently ignored unless the @option{-pedantic} option is added.
+
 @item -ff2c
 @opindex ff2c
 @cindex calling convention
@@ -1510,6 +1593,7 @@
 @item -fcheck=@var{<keyword>}
 @opindex @code{fcheck}
 @cindex array, bounds checking
+@cindex bit intrinsics checking
 @cindex bounds checking
 @cindex pointer checking
 @cindex memory checking
@@ -1534,6 +1618,10 @@
 
 Note: The warning is only printed once per location.
 
+@item @samp{bits}
+Enable generation of run-time checks for invalid arguments to the bit
+manipulation intrinsics.
+
 @item @samp{bounds}
 Enable generation of run-time checks for array subscripts
 and against the declared minimum and maximum values.  It also
@@ -1580,6 +1668,39 @@
 @c Note: This option is also referred in gcc's manpage
 Deprecated alias for @option{-fcheck=bounds}.
 
+@item -ftail-call-workaround
+@itemx -ftail-call-workaround=@var{n}
+@opindex @code{tail-call-workaround}
+Some C interfaces to Fortran codes violate the gfortran ABI by
+omitting the hidden character length arguments as described in
+@xref{Argument passing conventions}.  This can lead to crashes
+because pushing arguments for tail calls can overflow the stack.
+
+To provide a workaround for existing binary packages, this option
+disables tail call optimization for gfortran procedures with character
+arguments.  With @option{-ftail-call-workaround=2} tail call optimization
+is disabled in all gfortran procedures with character arguments,
+with @option{-ftail-call-workaround=1} or equivalent
+@option{-ftail-call-workaround} only in gfortran procedures with character
+arguments that call implicitly prototyped procedures.
+
+Using this option can lead to problems including crashes due to
+insufficient stack space.
+
+It is @emph{very strongly} recommended to fix the code in question.
+The @option{-fc-prototypes-external} option can be used to generate
+prototypes which conform to gfortran's ABI, for inclusion in the
+source code.
+
+Support for this option will likely be withdrawn in a future release
+of gfortran.
+
+The negative form, @option{-fno-tail-call-workaround} or equivalent
+@option{-ftail-call-workaround=0}, can be used to disable this option.
+
+Default is currently @option{-ftail-call-workaround}, this will change
+in future releases.
+
 @item -fcheck-array-temporaries
 @opindex @code{fcheck-array-temporaries}
 Deprecated alias for @option{-fcheck=array-temps}.
@@ -1618,7 +1739,7 @@
 bounds, and may not apply to all character variables.
 Future versions of GNU Fortran may improve this behavior.
 
-The default value for @var{n} is 32768.
+The default value for @var{n} is 65536.
 
 @item -fstack-arrays
 @opindex @code{fstack-arrays}
@@ -1655,6 +1776,34 @@
 GNU Fortran choose the smallest @code{INTEGER} kind a given
 enumerator set will fit in, and give all its enumerators this kind.
 
+@item -finline-arg-packing
+@opindex @code{finline-arg-packing}
+When passing an assumed-shape argument of a procedure as actual
+argument to an assumed-size or explicit size or as argument to a
+procedure that does not have an explicit interface, the argument may
+have to be packed, that is put into contiguous memory. An example is
+the call to @code{foo} in
+@smallexample
+  subroutine foo(a)
+     real, dimension(*) :: a
+  end subroutine foo
+  subroutine bar(b)
+     real, dimension(:) :: b
+     call foo(b)
+  end subroutine bar
+@end smallexample
+
+When @option{-finline-arg-packing} is in effect, this packing will be
+performed by inline code. This allows for more optimization while
+increasing code size.
+
+@option{-finline-arg-packing} is implied by any of the @option{-O} options
+except when optimizing for size via @option{-Os}.  If the code
+contains a very large number of argument that have to be packed, code
+size and also compilation time may become excessive.  If that is the
+case, it may be better to disable this option.  Instances of packing
+can be found by using by using @option{-Warray-temporaries}.
+
 @item -fexternal-blas
 @opindex @code{fexternal-blas}
 This option will make @command{gfortran} generate calls to BLAS functions
@@ -1742,6 +1891,11 @@
 optimizations may convert them into quiet NaN and that trapping
 needs to be enabled (e.g. via @option{-ffpe-trap}).
 
+The @option{-finit-integer} option will parse the value into an
+integer of type @code{INTEGER(kind=C_LONG)} on the host.  Said value
+is then assigned to the integer variables in the Fortran code, which
+might result in wraparound if the value is too large for the kind.
+
 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.
@@ -1828,7 +1982,7 @@
 
 @item -fc-prototypes
 @opindex @code{c-prototypes}
-@cindex Generating C prototypes from Fortran source code
+@cindex Generating C prototypes from Fortran BIND(C) enteties
 This option will generate C prototypes from @code{BIND(C)} variable
 declarations, types and procedure interfaces and writes them to
 standard output.  @code{ENUM} is not yet supported.
@@ -1847,6 +2001,32 @@
 @end smallexample
 where the C code intended for interoperating with the Fortran code
 then  uses @code{#include "foo.h"}.
+
+@item -fc-prototypes-external
+@opindex @code{c-prototypes-external}
+@cindex Generating C prototypes from external procedures
+This option will generate C prototypes from external functions and
+subroutines and write them to standard output.  This may be useful for
+making sure that C bindings to Fortran code are correct.  This option
+does not generate prototypes for @code{BIND(C)} procedures, use
+@option{-fc-prototypes} for that.
+
+The generated prototypes may need inclusion of an appropriate
+header, such as as @code{<stdint.h>} or @code{<stdlib.h>}.
+
+This is primarily meant for legacy code to ensure that existing C
+bindings match what @command{gfortran} emits.  The generated C
+prototypes should be correct for the current version of the compiler,
+but may not match what other compilers or earlier versions of
+@command{gfortran} need.  For new developments, use of the
+@code{BIND(C)} features is recommended.
+
+Example of use:
+@smallexample
+$ gfortran -fc-prototypes-external -fsyntax-only foo.f > foo.h
+@end smallexample
+where the C code intended for interoperating with the Fortran code
+then  uses @code{#include "foo.h"}.
 @end table
 
 @node Environment Variables