-@c Copyright (C) 1988, 89, 92-98, 1999 Free Software Foundation, Inc.
+@c Copyright (C) 1988, 89, 92-99, 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
-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
+-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
-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
-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
--malignment-traps
+-malignment-traps -mno-alignment-traps
-msoft-float -mhard-float -mfpe
-mthumb-interwork -mno-thumb-interwork
-mcpu= -march= -mfpe=
@emph{MN10300 Options}
-mmult-bug
-mno-mult-bug
+-mam33
+-mno-am33
-mrelax
@emph{M32R/D Options}
-m4650 -msingle-float -mmad
-mstats -EL -EB -G @var{num} -nocpp
-mabi=32 -mabi=n32 -mabi=64 -mabi=eabi
+-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
@emph{HPPA Options}
-march=@var{architecture type}
-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
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
-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.
+@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
+
+@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
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
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.
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.
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 -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 -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.
@end table
@node HPPA 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 @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}, or @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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