-@c Copyright (C) 1988, 89, 92-98, 1999 Free Software Foundation, Inc.
+@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@item C Language Options
@xref{C Dialect Options,,Options Controlling C Dialect}.
@smallexample
--ansi -flang-isoc9x -fallow-single-precision -fcond-mismatch -fno-asm
+-ansi -fstd -fallow-single-precision -fcond-mismatch -fno-asm
-fno-builtin -ffreestanding -fhosted -fsigned-bitfields -fsigned-char
-funsigned-bitfields -funsigned-char -fwritable-strings
-traditional -traditional-cpp -trigraphs
@item C++ Language Options
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
@smallexample
--fno-access-control -fcheck-new -fconserve-space -fdollars-in-identifiers
--fno-elide-constructors -fexternal-templates -ffor-scope
--fno-for-scope -fno-gnu-keywords -fguiding-decls
--fhonor-std -fhuge-objects -fno-implicit-templates -finit-priority
--fno-implement-inlines -fname-mangling-version-@var{n} -fno-default-inline
--foperator-names -fno-optional-diags -fpermissive -frepo -fstrict-prototype
--fsquangle -ftemplate-depth-@var{n} -fvtable-thunks
--nostdinc++ -Wctor-dtor-privacy -Wno-deprecated -Weffc++
--Wno-non-template-friend
--Wnon-virtual-dtor -Wold-style-cast -Woverloaded-virtual
--Wno-pmf-conversions -Wreorder -Wsign-promo -Wsynth
+-fno-access-control -fcheck-new -fconserve-space
+-fdollars-in-identifiers -fno-elide-constructors -fexternal-templates
+-ffor-scope -fno-for-scope -fno-gnu-keywords -fguiding-decls -fhonor-std
+-fhuge-objects -fno-implicit-templates -finit-priority
+-fno-implement-inlines -fname-mangling-version-@var{n}
+-fno-default-inline -fno-operator-names -fno-optional-diags -fpermissive
+-frepo -fstrict-prototype -fsquangle -ftemplate-depth-@var{n}
+-fuse-cxa-atexit -fvtable-thunks -nostdinc++ -Wctor-dtor-privacy
+-Wno-deprecated -Weffc++ -Wno-non-template-friend -Wnon-virtual-dtor
+-Wold-style-cast -Woverloaded-virtual -Wno-pmf-conversions -Wreorder
+-Wsign-promo -Wsynth
@end smallexample
@item Warning Options
-Werror-implicit-function-declaration -Wfloat-equal -Winline
-Wlarger-than-@var{len} -Wlong-long
-Wmain -Wmissing-declarations -Wmissing-noreturn
--Wmultichar -Wno-import
+-Wmultichar -Wno-import -Wpacked -Wpadded
-Wparentheses -Wpointer-arith -Wredundant-decls
-Wreturn-type -Wshadow -Wsign-compare -Wswitch
-Wtrigraphs -Wundef -Wuninitialized -Wunknown-pragmas -Wunreachable-code
-finline-functions -finline-limit=@var{n} -fkeep-inline-functions
-fmove-all-movables -fno-default-inline -fno-defer-pop
-fno-function-cse -fno-inline -fno-peephole
--fomit-frame-pointer -foptimize-register-moves -fregmove
--frerun-cse-after-loop -frerun-loop-opt -freduce-all-givs
+-fomit-frame-pointer -foptimize-register-moves -foptimize-sibling-calls
+-fregmove -frerun-cse-after-loop -frerun-loop-opt -freduce-all-givs
-fschedule-insns -fschedule-insns2 -fstrength-reduce
-fstrict-aliasing -fthread-jumps -funroll-all-loops
-funroll-loops
-mtune=@var{cpu type}
-mcmodel=@var{code model}
-m32 -m64
--mapp-regs -mbroken-saverestore -mcypress -mepilogue
--mflat -mfpu -mhard-float -mhard-quad-float
--mimpure-text -mlive-g0 -mno-app-regs -mno-epilogue
--mno-flat -mno-fpu -mno-impure-text
--mno-stack-bias -mno-unaligned-doubles
+-mapp-regs -mbroken-saverestore -mcypress
+-mepilogue -mfaster-structs -mflat
+-mfpu -mhard-float -mhard-quad-float
+-mimpure-text -mlive-g0 -mno-app-regs
+-mno-epilogue -mno-faster-structs -mno-flat -mno-fpu
+-mno-impure-text -mno-stack-bias -mno-unaligned-doubles
-msoft-float -msoft-quad-float -msparclite -mstack-bias
-msupersparc -munaligned-doubles -mv8
-mapcs-reentrant -mno-apcs-reentrant
-msched-prolog -mno-sched-prolog
-mlittle-endian -mbig-endian -mwords-little-endian
--mshort-load-bytes -mno-short-load-bytes -mshort-load-words -mno-short-load-words
+-malignment-traps -mno-alignment-traps
-msoft-float -mhard-float -mfpe
-mthumb-interwork -mno-thumb-interwork
-mcpu= -march= -mfpe=
-mstructure-size-boundary=
-mbsd -mxopen -mno-symrename
-mabort-on-noreturn
+-mlong-calls -mno-long-calls
-mnop-fun-dllimport -mno-nop-fun-dllimport
-msingle-pic-base -mno-single-pic-base
-mpic-register=
@emph{MN10300 Options}
-mmult-bug
-mno-mult-bug
+-mam33
+-mno-am33
-mrelax
@emph{M32R/D Options}
-mpowerpc -mpowerpc64 -mno-powerpc
-mpowerpc-gpopt -mno-powerpc-gpopt
-mpowerpc-gfxopt -mno-powerpc-gfxopt
--mnew-mnemonics -mno-new-mnemonics
+-mnew-mnemonics -mold-mnemonics
-mfull-toc -mminimal-toc -mno-fop-in-toc -mno-sum-in-toc
-m64 -m32 -mxl-call -mno-xl-call -mthreads -mpe
-msoft-float -mhard-float -mmultiple -mno-multiple
-m4650 -msingle-float -mmad
-mstats -EL -EB -G @var{num} -nocpp
-mabi=32 -mabi=n32 -mabi=64 -mabi=eabi
+-mfix7000 -mno-crt0
@emph{i386 Options}
-mcpu=@var{cpu type}
-mreg-alloc=@var{list} -mregparm=@var{num}
-malign-jumps=@var{num} -malign-loops=@var{num}
-malign-functions=@var{num} -mpreferred-stack-boundary=@var{num}
+-mthreads -mno-align-stringops -minline-all-stringops
+-mpush-args -maccumulate-outgoing-args
@emph{HPPA Options}
-march=@var{architecture type}
-m32032 -m32332 -m32532 -m32081 -m32381 -mmult-add -mnomult-add
-msoft-float -mrtd -mnortd -mregparam -mnoregparam -msb -mnosb
-mbitfield -mnobitfield -mhimem -mnohimem
+
+@emph{AVR Options}
+-mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts
+-mcall-prologues
+
+@emph{MCore Options}
+-mhardlit, -mno-hardlit -mdiv -mno-div -mrelax-immediates
+-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields
+-m4byte-functions -mno-4byte-functions -mcallgraph-data
+-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim
+-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment
@end smallexample
@item Code Generation Options
-freg-struct-return -fshared-data -fshort-enums
-fshort-double -fvolatile -fvolatile-global -fvolatile-static
-fverbose-asm -fpack-struct -fstack-check
+-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym}
-fargument-alias -fargument-noalias
-fargument-noalias-global
-fleading-underscore
@cindex ANSI support
@item -ansi
In C mode, support all ANSI standard C programs. In C++ mode,
-remove GNU extensions that conflict with ANSI C++.
+remove GNU extensions that conflict with ISO C++.
@c shouldn't we be saying "ISO"?
This turns off certain features of GCC that are incompatible with ANSI
-C (when compiling C code), or of ANSI standard C++ (when compiling C++ code),
+C (when compiling C code), or of standard C++ (when compiling C++ code),
such as the @code{asm} and @code{typeof} keywords, and
predefined macros such as @code{unix} and @code{vax} that identify the
type of system you are using. It also enables the undesirable and
rarely used ANSI trigraph feature. For the C compiler,
it disables recognition of C++ style @samp{//} comments as well as
-the @code{inline} keyword. For the C++ compiler,
-@samp{-foperator-names} is enabled as well.
-
+the @code{inline} keyword.
The alternate keywords @code{__asm__}, @code{__extension__},
@code{__inline__} and @code{__typeof__} continue to work despite
The functions @code{alloca}, @code{abort}, @code{exit}, and
@code{_exit} are not builtin functions when @samp{-ansi} is used.
-@item -flang-isoc9x
-Enable support for features found in the C9X standard. In particular,
-enable support for the C9X @code{restrict} keyword.
+@item -fstd=
+Determine the language standard. A value for this option must be provided;
+possible values are
+
+@itemize @minus
+@item iso9899:1990
+Same as -ansi
+
+@item iso9899:199409
+ISO C as modified in amend. 1
+
+@item iso9899:199x
+ISO C 9x
+
+@item c89
+same as -std=iso9899:1990
+
+@item c9x
+same as -std=iso9899:199x
+
+@item gnu89
+default, iso9899:1990 + gnu extensions
-Even when this option is not specified, you can still use some C9X
-features in so far as they do not conflict with previous C standards.
-For example, you may use @code{__restrict__} even when -flang-isoc9x
-is not specified.
+@item gnu9x
+iso9899:199x + gnu extensions
+@end itemize
+
+Even when this option is not specified, you can still use some of the
+features of newer standards in so far as they do not conflict with
+previous C standards. For example, you may use @code{__restrict__} even
+when -fstd=c9x is not specified.
@item -fno-asm
Do not recognize @code{asm}, @code{inline} or @code{typeof} as a
Specifying this option disables that optimization, and forces g++ to
call the copy constructor in all cases.
+@item -fno-enforce-eh-specs
+Don't check for violation of exception specifications at runtime. This
+option violates the C++ standard, but may be useful for reducing code
+size in production builds, much like defining @samp{NDEBUG}. The compiler
+will still optimize based on the exception specifications.
+
@item -fexternal-templates
Cause template instantiations to obey @samp{#pragma interface} and
@samp{implementation}; template instances are emitted or not according
@itemx -fno-for-scope
If -ffor-scope is specified, the scope of variables declared in
a @i{for-init-statement} is limited to the @samp{for} loop itself,
-as specified by the draft C++ standard.
+as specified by the C++ standard.
If -fno-for-scope is specified, the scope of variables declared in
a @i{for-init-statement} extends to the end of the enclosing scope,
as was the case in old versions of gcc, and other (traditional)
otherwise be invalid, or have different behavior.
@item -fno-gnu-keywords
-Do not recognize @code{classof}, @code{headof}, or @code{typeof} as a
-keyword, so that code can use these words as identifiers. You can use
-the keywords @code{__classof__}, @code{__headof__}, and
-@code{__typeof__} instead. @samp{-ansi} implies
-@samp{-fno-gnu-keywords}.
+Do not recognize @code{typeof} as a keyword, so that code can use these
+words as identifiers. You can use the keywords @code{__typeof__}
+instead. @samp{-ansi} implies @samp{-fno-gnu-keywords}.
@item -fguiding-decls
Treat a function declaration with the same type as a potential function
Like all options that change the ABI, all C++ code, @emph{including
libgcc} must be built with the same setting of this option.
+@item -fmessage-length=@var{n}
+Try to format error messages so that they fit on lines of about @var{n}
+characters. The default is 72 characters. If @var{n} is zero, then no
+line-wrapping will be done; each error message will appear on a single
+line.
+
@item -fno-implicit-templates
Never emit code for non-inline templates which are instantiated
implicitly (i.e. by use); only emit code for explicit instantiations.
Like all options that change the ABI, all C++ code, @emph{including
libgcc} must be built with the same setting of this option.
-@item -foperator-names
-Recognize the operator name keywords @code{and}, @code{bitand},
+@item -fno-operator-names
+Do not treat the operator name keywords @code{and}, @code{bitand},
@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as
-synonyms for the symbols they refer to. @samp{-ansi} implies
-@samp{-foperator-names}.
+synonyms as keywords.
@item -fno-optional-diags
Disable diagnostics that the standard says a compiler does not need to
endless recursions during template class instantiation. ANSI/ISO C++
conforming programs must not rely on a maximum depth greater than 17.
+@item -fuse-cxa-atexit
+Register destructors for objects with static storage duration with the
+@code{__cxa_atexit} function rather than the @code{atexit} function.
+This option is required for fully standards-compliant handling of static
+destructors, but will only work if your C library supports
+@code{__cxa_atexit}.
+
@item -fvtable-thunks
Use @samp{thunks} to implement the virtual function dispatch table
(@samp{vtable}). The traditional (cfront-style) approach to
Warn if a multicharacter constant (@samp{'FOOF'}) is used. Usually they
indicate a typo in the user's code, as they have implementation-defined
values, and should not be used in portable code.
-
+
@item -Wparentheses
Warn if parentheses are omitted in certain contexts, such
as when there is an assignment in a context where a truth value
@item -Wfloat-equal
Warn if floating point values are used in equality comparisons.
+The idea behind this is that sometimes it is convenient (for the
+programmer) to consider floating-point values as approximations to
+infinitely precise real numbers. If you are doing this, then you need
+to compute (by analysing the code, or in some other way) the maximum or
+likely maximum error that the computation introduces, and allow for it
+when performing comparisons (and when producing output, but that's a
+different problem). In particular, instead of testing for equality, you
+would check to see whether the two values have ranges that overlap; and
+this is done with the relational operators, so equality comparisons are
+probably mistaken.
+
@item -Wtraditional (C only)
Warn about certain constructs that behave differently in traditional and
ANSI C.
@item
A non-@code{static} function declaration follows a @code{static} one.
This construct is not accepted by some traditional C compilers.
+
+@item
+The ANSI type of an integer constant has a different width or
+signedness from its traditional type. This warning is only issued if
+the base of the constant is ten. I.e. hexadecimal or octal values, which
+typically represent bit patterns, are not warned about.
+
+@item
+Usage of ANSI string concatenation is detected.
@end itemize
@item -Wundef
adding the @code{noreturn} attribute, otherwise subtle code generation
bugs could be introduced.
+@item -Wpacked
+Warn if a structure is given the packed attribute, but the packed
+attribute has no effect on the layout or size of the structure.
+Such structures may be mis-aligned for little benefit. For
+instance, in this code, the variable @code{f.x} in @code{struct bar}
+will be misaligned even though @code{struct bar} does not itself
+have the packed attribute:
+
+@smallexample
+@group
+struct foo @{
+ int x;
+ char a, b, c, d;
+@} __attribute__((packed));
+struct bar @{
+ char z;
+ struct foo f;
+@};
+@end group
+@end smallexample
+
+@item -Wpadded
+Warn if padding is included in a structure, either to align an element
+of the structure or to align the whole structure. Sometimes when this
+happens it is possible to rearrange the fields of the structure to
+reduce the padding and so make the structure smaller.
+
@item -Wredundant-decls
Warn if anything is declared more than once in the same scope, even in
cases where multiple declaration is valid and changes nothing.
in many functions. @strong{It also makes debugging impossible on
some machines.}
+@item -foptimize-sibling-calls
+Optimize sibling and tail recursive calls.
+
@ifset INTERNALS
On some machines, such as the Vax, this flag has no effect, because
the standard calling sequence automatically handles the frame pointer
Like %@{@code{S}*@}, but don't put a blank between a switch and its
argument. Thus %@{^o*@} would only generate one argument, not two.
+@item %@{<@code{S}@}
+Remove all occurences of @code{S} from the command line. Note - this
+command is position dependent. @samp{%} commands in the spec string
+before this option will see @code{S}, @samp{%} commands in the spec
+string after this option will not.
+
@item %@{@code{S}*:@code{X}@}
Substitutes @code{X} if one or more switches whose names start with
@code{-S} are specified to GCC. Note that the tail part of the
* V850 Options::
* ARC Options::
* NS32K Options::
+* AVR Options::
+* MCore Options::
@end menu
@node M680x0 Options
generated by other compilers. It is not the default because it results
in a performance loss, especially for floating point code.
+@item -mno-faster-structs
+@itemx -mfaster-structs
+With @samp{-mfaster-structs}, the compiler assumes that structures
+should have 8 byte alignment. This enables the use of pairs of
+@code{ldd} and @code{std} instructions for copies in structure
+assignment, in place of twice as many @code{ld} and @code{st} pairs.
+However, the use of this changed alignment directly violates the Sparc
+ABI. Thus, it's intended only for use on targets where the developer
+acknowledges that their resulting code will not be directly in line with
+the rules of the ABI.
+
@item -mv8
@itemx -msparclite
These two options select variations on the SPARC architecture.
big-endian ARM processors generated by versions of the compiler prior to
2.8.
+@item -malignment-traps
+@kindex -malignment-traps
+Generate code that will not trap if the MMU has alignment traps enabled.
+On ARM architectures prior to ARMv4, there were no instructions to
+access half-word objects stored in memory. However, when reading from
+memory a feature of the ARM architecture allows a word load to be used,
+even if the address is unaligned, and the processor core will rotate the
+data as it is being loaded. This option tells the compiler that such
+misaligned accesses will cause a MMU trap and that it should instead
+synthesise the access as a series of byte accesses. The compiler can
+still use word accesses to load half-word data if it knows that the
+address is aligned to a word boundary.
+
+This option is ignored when compiling for ARM architecture 4 or later,
+since these processors have instructions to directly access half-word
+objects in memory.
+
+@item -mno-alignment-traps
+@kindex -mno-alignment-traps
+Generate code that assumes that the MMU will not trap unaligned
+accesses. This produces better code when the target instruction set
+does not have half-word memory operations (implementations prior to
+ARMv4).
+
+Note that you cannot use this option to access unaligned word objects,
+since the processor will only fetch one 32-bit aligned object from
+memory.
+
+The default setting for most targets is -mno-alignment-traps, since
+this produces better code when there are no half-word memory
+instructions available.
+
@item -mshort-load-bytes
@kindex -mshort-load-bytes
-Do not try to load half-words (eg @samp{short}s) by loading a word from
-an unaligned address. For some targets the MMU is configured to trap
-unaligned loads; use this option to generate code that is safe in these
-environments.
+This is a depreciated alias for @samp{-malignment-traps}.
@item -mno-short-load-bytes
@kindex -mno-short-load-bytes
-Use unaligned word loads to load half-words (eg @samp{short}s). This
-option produces more efficient code, but the MMU is sometimes configured
-to trap these instructions.
+This is a depreciated alias for @samp{-mno-alignment-traps}.
@item -mshort-load-words
@kindex -mshort-load-words
-This is a synonym for @samp{-mno-short-load-bytes}.
+This is a depreciated alias for @samp{-mno-alignment-traps}.
@item -mno-short-load-words
@kindex -mno-short-load-words
-This is a synonym for @samp{-mshort-load-bytes}.
+This is a depreciated alias for @samp{-malignment-traps}.
@item -mbsd
@kindex -mbsd
Generate a call to the function abort at the end of a noreturn function.
It will be executed if the function tries to return.
+@item -mlong-calls
+@itemx -mno-long-calls
+Tells the compiler to perform function calls by first loading the
+address of the function into a register and then performing a subroutine
+call on this register. This switch is needed if the target function
+will lie outside of the 64 megabyte addressing range of the offset based
+version of subroutine call instruction.
+
+Even if this switch is enabled, not all function calls will be turned
+into long calls. The heuristic is that static functions, functions
+which have the @samp{short-call} attribute, functions that are inside
+the scope of a @samp{#pragma no_long_calls} directive and functions whose
+definitions have already been compiled within the current compilation
+unit, will not be turned into long calls. The exception to this rule is
+that weak function defintions, functions with the @samp{long-call}
+attribute or the @samp{section} attribute, and functions that are within
+the scope of a @samp{#pragma long_calls} directive, will always be
+turned into long calls.
+
+This feature is not enabled by default. Specifying
+@samp{--no-long-calls} will restore the default behaviour, as will
+placing the function calls within the scope of a @samp{#pragma
+long_calls_off} directive. Note these switches have no effect on how
+the compiler generates code to handle function calls via function
+pointers.
+
@item -mnop-fun-dllimport
@kindex -mnop-fun-dllimport
Disable the support for the @emph{dllimport} attribute.
Do not generate code to avoid bugs in the multiply instructions for the
MN10300 processors.
+@item -mam33
+Generate code which uses features specific to the AM33 processor.
+
+@item -mno-am33
+Do not generate code which uses features specific to the AM33 processor. This
+is the default.
+
@item -mrelax
Indicate to the linker that it should perform a relaxation optimization pass
to shorten branches, calls and absolute memory addresses. This option only
@item -nocpp
Tell the MIPS assembler to not run its preprocessor over user
assembler files (with a @samp{.s} suffix) when assembling them.
+
+@item -mfix7000
+Pass an option to gas which will cause nops to be inserted if
+the read of the destination register of an mfhi or mflo instruction
+occurs in the following two instructions.
+
+@item -no-crt0
+Do not include the default crt0.
@end table
@ifset INTERNALS
to stack space usage, such as embedded systems and operating system kernels,
may want to reduce the preferred alignment to
@samp{-mpreferred-stack-boundary=2}.
+
+@item -mpush-args
+@kindex -mpush-args
+Use PUSH operations to store outgoing parameters. This method is shorter
+and usually equally fast as method using SUB/MOV operations and is enabled
+by default. In some cases disabling it may improve performance because of
+improved scheduling and reduced dependencies.
+
+@item -maccumulate-outgoing-args
+@kindex -maccumulate-outgoing-args
+If enabled, the maximum amount of space required for outgoing arguments will be
+computed in the function prologue. This in faster on most modern CPUs
+because of reduced dependecies, improved scheduling and reduced stack usage
+when preferred stack boundary is not equal to 2. The drawback is a notable
+increase in code size. This switch implies -mno-push-args.
+
+@item -mthreads
+@kindex -mthreads
+Support thread-safe exception handling on @samp{Mingw32}. Code that relies
+on thread-safe exception handling must compile and link all code with the
+@samp{-mthreads} option. When compiling, @samp{-mthreads} defines
+@samp{-D_MT}; when linking, it links in a special thread helper library
+@samp{-lmingwthrd} which cleans up per thread exception handling data.
+
+@item -mno-align-stringops
+@kindex -mno-align-stringops
+Do not align destination of inlined string operations. This switch reduces
+code size and improves performance in case the destination is already aligned,
+but gcc don't know about it.
+
+@item -minline-all-stringops
+@kindex -minline-all-stringops
+By default GCC inlines string operations only when destination is known to be
+aligned at least to 4 byte boundary. This enables more inlining, increase code
+size, but may improve performance of code that depends on fast memcpy, strlen
+and memset for short lengths.
@end table
@node HPPA Options
@end table
+@node AVR Options
+@subsection AVR Options
+@cindex AVR Options
+
+These options are defined for AVR implementations:
+
+@table @code
+@item -mmcu=@var{mcu}
+Specify ATMEL AVR mcu (at90s23xx,attiny22,at90s44xx,at90s85xx,atmega603,
+atmega103).
+
+@item -msize
+Output instruction size's to the asm file
+
+@item -minit-stack=@var{N}
+Specify the initial stack address
+
+@item -mno-interrupts
+Generated code is not compatible with hardware interrupts.
+Code size will be smaller.
+
+@item -mcall-prologues
+Functions prologues/epilogues expanded as call to appropriate
+subroutines. Code size will be smaller.
+@end table
+
+@node MCore Options
+@subsection MCore Options
+@cindex MCore options
+
+These are the @samp{-m} options defined for the Motorola M*Core
+processors.
+
+@table @code
+
+@item -mhardlit
+@itemx -mhardlit
+@itemx -mno-hardlit
+Inline constants into the code stream if it can be done in two
+instructions or less.
+
+@item -mdiv
+@itemx -mdiv
+@itemx -mno-div
+Use the divide instruction. (Enabled by default).
+
+@item -mrelax-immediate
+@itemx -mrelax-immediate
+@itemx -mno-relax-immediate
+Allow arbitary sized immediated in bit operations.
+
+@item -mwide-bitfields
+@itemx -mwide-bitfields
+@itemx -mno-wide-bitfields
+Always treat bitfields as int-sized.
+
+@item -m4byte-functions
+@itemx -m4byte-functions
+@itemx -mno-4byte-functions
+Force all functions to be aligfned to a four byte boundary.
+
+@item -mcallgraph-data
+@itemx -mcallgraph-data
+@itemx -mno-callgraph-data
+Emit callgraph information.
+
+@item -mslow-bytes
+@itemx -mslow-bytes
+@itemx -mno-slow-bytes
+Prefer word access when reading byte quantities.
+
+@item -mlittle-endian
+@itemx -mlittle-endian
+@itemx -mbig-endian
+Genreate code for a little endian target.
+
+@item -m210
+@itemx -m210
+@itemx -m340
+Generate code for the 210 processor.
+
+@end table
@node Code Gen Options
a single-threaded environment since stack overflow is automatically
detected on nearly all systems if there is only one stack.
+Note that this switch does not actually cause checking to be done; the
+operating system must do that. The switch causes generation of code
+to ensure that the operating system sees the stack being extended.
+
+@item -fstack-limit-register=@var{reg}
+@itemx -fstack-limit-symbol=@var{sym}
+@itemx -fno-stack-limit
+Generate code to ensure that the stack does not grow beyond a certain value,
+either the value of a register or the address of a symbol. If the stack
+would grow beyond the value, a signal is raised. For most targets,
+the signal is raised before the stack overruns the boundary, so
+it is possible to catch the signal without taking special precautions.
+
+For instance, if the stack starts at address @samp{0x80000000} and grows
+downwards you can use the flags
+@samp{-fstack-limit-symbol=__stack_limit}
+@samp{-Wl,--defsym,__stack_limit=0x7ffe0000} which will enforce a stack
+limit of 128K.
+
@cindex aliasing of parameters
@cindex parameters, aliased
@item -fargument-alias
The output from @code{protoize} or @code{unprotoize} replaces the
original source file. The original file is renamed to a name ending
-with @samp{.save}. If the @samp{.save} file already exists, then
-the source file is simply discarded.
+with @samp{.save} (for DOS, the saved filename ends in @samp{.sav}
+without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav}
+for DOS) file already exists, then the source file is simply discarded.
@code{protoize} and @code{unprotoize} both depend on GCC itself to
scan the program and collect information about the functions it uses.
the @var{compilation-options}, they are ignored.
@item -C
-Rename files to end in @samp{.C} instead of @samp{.c}.
-This is convenient if you are converting a C program to C++.
-This option applies only to @code{protoize}.
+Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file
+systems) instead of @samp{.c}. This is convenient if you are converting
+a C program to C++. This option applies only to @code{protoize}.
@item -g
Add explicit global declarations. This means inserting explicit
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