gcc.1

这是完整的gcc源代码

I am interested in hearing about the difference this makes.
.TP
.B \-fforce-mem
Force memory operands to be copied into registers before doing
arithmetic on them.
This may produce better code by making all memory references
potential common subexpressions.
When they are not common subexpressions, instruction combination should
eliminate the separate register-load.
I am interested in hearing about the difference this makes.
.TP
.B \-fforce-addr
Force memory address constants to be copied into registers before
doing arithmetic on them.
This may produce better code just as
.B \-fforce-mem
may.
I am interested in hearing about the difference this makes.
.TP
.B \-fomit-frame-pointer
Don't keep the frame pointer in a register for functions that
don't need one.
This avoids the instructions to save, set up and restore frame pointers;
it also makes an extra register available in many functions.
.B "It also makes debugging impossible."
.sp
On some machines, such as the Vax, this flag has no effect, because
the standard calling sequence automatically handles the frame pointer
and nothing is saved by pretending it doesn't exist.
The machine-description macro
.B FRAME_POINTER_REQUIRED
controls whether a target machine supports this flag.
.TP
.B \-finline-functions
Integrate all simple functions into their callers.
The compiler heuristically decides which functions are simple
enough to be worth integrating in this way.
.sp
If all calls to a given function are integrated, and the function is declared
.BR static ,
then the function is normally not output as assembler code in its own right.
.TP
.B \-fcaller-saves
Enable values to be allocated in registers that will be clobbered by
function calls, by emitting extra instructions to save and restore the
registers around such calls.
Such allocation is done only when it seems to result in better code than
would otherwise be produced.
.sp
This option is enabled by default on certain machines, usually those
which have no call-preserved registers to use instead.
.TP
.B \-fkeep-inline-functions
Even if all calls to a given function are integrated, and the function is
declared
.BR static ,
nevertheless output a separate run-time callable version of the function.
.TP
.B \-fwritable-strings
Store string constants in the writable data segment and don't uniquize them.
This is for compatibility with old programs which assume they can write
into string constants.
Writing into string constants is a very bad idea;
constants should be constant.
.TP
.B \-fcond-mismatch
Allow conditional expressions with mismatched types in the second and
third arguments.
The value of such an expression is void.
.TP
.B \-fno-function-cse
Do not put function addresses in registers; make each instruction that
calls a constant function contain the function's address explicitly.
.sp
This option results in less efficient code, but some strange hacks that
alter the assembler output may be confused by the optimizations performed
when this option is not used.
.TP
.B \-fvolatile
Consider all memory references through pointers to be volatile.
.TP
.B \-fshared-data
Requests that the data and
.RB non- const
variables of this compilation be shared data rather than private data.
The distinction makes sense only on certain operating systems, where
shared data is shared between processes running the same program, while
private data exists in one copy per process.
.TP
.B \-funsigned-char
Let the type
.B char
be the unsigned, like
.BR "unsigned char" .
.sp
Each kind of machine has a default for what
.B char
should be.
It is either like
.B "unsigned char"
by default or like
.B "signed char"
by default.
(Actually, at present, the default is always signed.)
.sp
The type
.B char
is always a distinct type from either
.B "signed char"
or
.BR "unsigned char" ,
even though its behavior is always just like one of those two.
.sp
Note that this is equivalent to
.BR \-fno-signed-char ,
which is the negative form of
.BR \-fsigned-char .
.TP
.B \-fsigned-char
Let the type
.B char
be signed, like
.BR "signed char" .
.sp
Note that this is equivalent to
.BR \-fno-unsigned-char ,
which is the negative form of
.BR \-funsigned-char .
.TP
.B \-fdelayed-branch
If supported for the target machine, attempt to reorder instructions to
exploit instruction slots available after delayed branch instructions.
.TP
.BI \-ffixed- reg
Treat the register named
.I reg
as a fixed register; generated code should never refer to it
(except perhaps as a stack pointer, frame pointer or in some other fixed role).
.sp
.I reg
must be the name of a register.
The register names accepted are machine-specific and are defined in the
.B REGISTER_NAMES
macro in the machine description macro file.
.sp
This flag does not have a negative form, because it specifies a
three-way choice.
.TP
.BI \-fcall-used- reg
Treat the register named
.I reg
as an allocatable register that is clobbered by function calls.
It may be allocated for temporaries or variables that do not live
across a call.
Functions compiled this way will not save and restore the register REG.
.sp
Use of this flag for a register that has a fixed pervasive role
in the machine's execution model, such as the stack pointer or
frame pointer, will produce disastrous results.
.sp
This flag does not have a negative form, because it specifies a
three-way choice.
.TP
.BI \-fcall-saved- reg
Treat the register named
.I reg
as an allocatable register saved by functions.
It may be allocated even for temporaries or variables that live across a call.
Functions compiled this way will save and restore the register
.I reg
if they use it.
.sp
Use of this flag for a register that has a fixed pervasive role
in the machine's execution model, such as the stack pointer or
frame pointer, will produce disastrous results.
.sp
A different sort of disaster will result from the use of this
flag for a register in which function values may be returned.
.sp
This flag does not have a negative form, because it specifies a
three-way choice.
.TP
.BI \-d letters
Says to make debugging dumps at times specified by
.IR letters .
Here are the possible letters:
.sp
.B r
.in +.5i
Dump after RTL generation.
.in -.5i
.B j
.in +.5i
Dump after first jump optimization.
.in -.5i
.B J
.in +.5i
Dump after last jump optimization.
.in -.5i
.B s
.in +.5i
Dump after CSE (including the jump optimization that sometimes follows CSE).
.in -.5i
.B L
.in +.5i
Dump after loop optimization.
.in -.5i
.B f
.in +.5i
Dump after flow analysis.
.in -.5i
.B c
.in +.5i
Dump after instruction combination.
.in -.5i
.B l
.in +.5i
Dump after local register allocation.
.in -.5i
.B g
.in +.5i
Dump after global register allocation.
.in -.5i
.B d
.in +.5i
Dump after delayed branch scheduling.
.in -.5i
.B m
.in +.5i
Print statistics on memory usage, at the end of the run.
.in -.5i
.TP
.B \-pedantic
Issue all the warnings demanded by strict ANSI standard C; reject
all programs that use forbidden extensions.
.sp
Valid ANSI standard C programs should compile properly with or without
this option (though a rare few will require
.BR \-ansi ).
However, without this option, certain GNU extensions and traditional C
features are supported as well.
With this option, they are rejected.
There is no reason to use this option; it exists only to satisfy pedants.
.sp
.B \-pedantic
does not cause warning messages for use of the alternate keywords whose
names begin and end with
.BR __ .
.TP
.B \-static
On Suns running version 4, this prevents linking with the shared
libraries.
.RB ( \-g
has the same effect.)
.P
These options control the C preprocessor, which is run on each C source
file before actual compilation.  If you use the `-E' option, nothing
is done except C preprocessing.  Some of these options make sense only
together with `-E' because they request preprocessor output that is
not suitable for actual compilation.
.TP
.B \-C
Tell the preprocessor not to discard comments.
Used with the
.B \-E
option.
.TP
.BI \-I dir
Search directory
.I dir
for include files.
.TP
.B \-I-
Any directories specified with
.B \-I
options before the
.B \-I-
option are searched only for the case of
.B #include
\fB"\fIfile\fB"\fR; they are not searched for
.BR "#include <\fIfile\fB>" .
.sp
If additional directories are specified with
.B \-I
options after the
.BR \-I- ,
these directories are searched for all
.B #include
directives.
(Ordinarily
.I all
.B \-I
directories are used this way.)
.sp
In addition, the
.B \-I-
option inhibits the use of the current directory as the first
search directory for
.B #include
\fB"\fIfile\fB"\fR.
Therefore, the current directory is searched only if it is requested
explicitly with
.BR \-I. .
Specifying both
.B \-I-
and
.B -I.
allows you to control precisely which directories are searched before
the current one and which are searched after.
.TP
.B \-nostdinc
Do not search the standard system directories for header files.
Only the directories you have specified with
.B \-I
options (and the current directory, if appropriate) are searched.
.sp
Between
.B \-nostdinc
and
.BR \-I- ,
you can eliminate all directories from the search path
except those you specify.
.TP
.B \-M
Tell the preprocessor to output a rule suitable for
.BI make (1)
describing the dependencies of each source file.
For each source file, the preprocessor outputs one
.BR make -rule
whose target is the object file name for that source file and whose
dependencies are all the files
.BR #include d
in it.
This rule may be a single line or may be continued with
.B \\\\-newline
if it is long.
.sp
.B \-M
implies
.BR \-E .
.TP
.B \-MM
Like
.B \-M
but the output mentions only the user-header files included with
.B #include
\fB"\fIfile\fB"\fR.
System header files included with
.B "#include <\fIfile\fB>"
are omitted.
.sp
.B \-MM
implies
.BR \-E .
.TP
.BI \-D macro
Define macro
.I macro
with the empty string as its definition.
.TP
.BI \-D macro\fR=\fIdefn
Define macro
.I macro
as
.IR defn .
.TP
.BI \-U macro
Undefine macro
.IR macro .
.TP
.B \-trigraphs
Support ANSI C trigraphs.
You don't want to know about this brain-damage.
The
.B \-ansi
option also has this effect.
.SH FILES
.ta \w'LIBDIR/gcc-include 'u
file.c	C source file
.br
file.s	assembly language file
.br
file.o	object file
.br
a.out	link edited output
.br
/tmp/cc\(**	temporary files
.br
\fILIBDIR\fR/gcc-cpp	preprocessor
.br
\fILIBDIR\fR/gcc-cc1	compiler
.br
\fILIBDIR\fR/gcc-gnulib	library needed by GCC on some machines
.br
/lib/crt[01n].o	start-up routine
.br
/lib/libc.a	standard C library, see
.IR intro (3)
.br
/usr/include	standard directory for 
.B #include
files
.br
\fILIBDIR\fR/gcc-include	standard gcc directory for
.B #include
files
.sp
.I LIBDIR
is usually
.BR /usr/local/lib .
.SH "SEE ALSO"
as(1), ld(1), adb(1), dbx(1), sdb(1).
.SH BUGS
Bugs should be reported to
.BR [e-mail] .
Bugs tend actually to be fixed if they can be isolated, so it is in your
interest to report them in such a way that they can be easily reproduced.
.SH COPYING
Copyright (c) 1988 Free Software Foundation, Inc.
.P
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
.P
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
.P
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be included in
translations approved by the Free Software Foundation instead of in
the original English.
.SH AUTHORS
See the GNU CC Manual for the contributors to GNU CC.