g++.1

gcc-2.95.3 Linux下最常用的C编译器

\&\|'.
.TP
.B \-g
Produce debugging information in the operating system's native format
(for DBX or SDB or DWARF).  GDB also can work with this debugging
information.  On most systems that use DBX format, `\|\c
.B \-g\c
\&\|' enables use
of extra debugging information that only GDB can use.

Unlike most other C compilers, GNU CC allows you to use `\|\c
.B \-g\c
\&\|' with
`\|\c
.B \-O\c
\&\|'.  The shortcuts taken by optimized code may occasionally
produce surprising results: some variables you declared may not exist
at all; flow of control may briefly move where you did not expect it;
some statements may not be executed because they compute constant
results or their values were already at hand; some statements may
execute in different places because they were moved out of loops.

Nevertheless it proves possible to debug optimized output.  This makes
it reasonable to use the optimizer for programs that might have bugs.
.TP
.BI "\-I" "dir"\c
\&
Append directory \c
.I dir\c
\& to the list of directories searched for include files.
.TP
.BI "\-L" "dir"\c
\&
Add directory \c
.I dir\c
\& to the list of directories to be searched
for `\|\c
.B \-l\c
\&\|'.
.TP
.BI \-l library\c
\&
Use the library named \c
.I library\c
\& when linking.  (C++ programs often require `\|\c
\-lg++\c
\&\|' for successful linking.)
.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.
.TP
.B \-nostdinc++
Do not search for header files in the standard directories specific to
C++, but do still search the other standard directories.  (This option
is used when building libg++.)
.TP
.B \-O
Optimize.  Optimizing compilation takes somewhat more time, and a lot
more memory for a large function.
.TP
.BI "\-o " file\c
\&
Place output in file \c
.I file\c
\&.
.TP
.B \-S
Stop after the stage of compilation proper; do not assemble.  The output
is an assembler code file for each non-assembler input
file specified.
.TP
.B \-traditional
Attempt to support some aspects of traditional C compilers.

Specifically, for both C and C++ programs:
.TP
\ \ \ \(bu
In the preprocessor, comments convert to nothing at all, rather than
to a space.  This allows traditional token concatenation.
.TP
\ \ \ \(bu
In the preprocessor, macro arguments are recognized within string
constants in a macro definition (and their values are stringified,
though without additional quote marks, when they appear in such a
context).  The preprocessor always considers a string constant to end
at a newline.
.TP
\ \ \ \(bu
The preprocessor does not predefine the macro \c
.B __STDC__\c
\& when you use
`\|\c
.B \-traditional\c
\&\|', but still predefines\c
.B __GNUC__\c
\& (since the GNU extensions indicated by 
.B __GNUC__\c
\& are not affected by
`\|\c
.B \-traditional\c
\&\|').  If you need to write header files that work
differently depending on whether `\|\c
.B \-traditional\c
\&\|' is in use, by
testing both of these predefined macros you can distinguish four
situations: GNU C, traditional GNU C, other ANSI C compilers, and
other old C compilers.
.PP
.TP
\ \ \ \(bu
String ``constants'' are not necessarily constant; they are stored in
writable space, and identical looking constants are allocated
separately.

For C++ programs only (not C), `\|\c
.B \-traditional\c
\&\|' has one additional effect: assignment to 
.B this
is permitted.  This is the same as the effect of `\|\c
.B \-fthis\-is\-variable\c
\&\|'.
.TP
.BI \-U macro
Undefine macro \c
.I macro\c
\&.
.TP
.B \-Wall
Issue warnings for conditions which pertain to usage that we recommend
avoiding and that we believe is easy to avoid, even in conjunction
with macros. 
.TP
.B \-Wenum\-clash
Warn when converting between different enumeration types.
.TP
.B \-Woverloaded\-virtual
In a derived class, the definitions of virtual functions must match
the type signature of a virtual function declared in the base class.
Use this option to request warnings when a derived class declares a
function that may be an erroneous attempt to define a virtual
function: that is, warn when a function with the same name as a
virtual function in the base class, but with a type signature that
doesn't match any virtual functions from the base class.
.TP
.B \-Wtemplate\-debugging
When using templates in a C++ program, warn if debugging is not yet
fully available.
.TP
.B \-w
Inhibit all warning messages.
.TP
.BI +e N
Control how virtual function definitions are used, in a fashion
compatible with
.B cfront
1.x.
.PP

.SH PRAGMAS
Two `\|\c
.B #pragma\c
\&\|' directives are supported for GNU C++, to permit using the same
header file for two purposes: as a definition of interfaces to a given
object class, and as the full definition of the contents of that object class.
.TP
.B #pragma interface
Use this directive in header files that define object classes, to save
space in most of the object files that use those classes.  Normally,
local copies of certain information (backup copies of inline member
functions, debugging information, and the internal tables that
implement virtual functions) must be kept in each object file that
includes class definitions.  You can use this pragma to avoid such
duplication.  When a header file containing `\|\c
.B #pragma interface\c
\&\|' is included in a compilation, this auxiliary information
will not be generated (unless the main input source file itself uses
`\|\c
.B #pragma implementation\c
\&\|').  Instead, the object files will contain references to be
resolved at link time.  
.tr !"
.TP
.B #pragma implementation
.TP
.BI "#pragma implementation !" objects .h!
Use this pragma in a main input file, when you want full output from
included header files to be generated (and made globally visible).
The included header file, in turn, should use `\|\c
.B #pragma interface\c
\&\|'.  
Backup copies of inline member functions, debugging information, and
the internal tables used to implement virtual functions are all
generated in implementation files.

If you use `\|\c
.B #pragma implementation\c
\&\|' with no argument, it applies to an include file with the same
basename as your source file; for example, in `\|\c
.B allclass.cc\c
\&\|', `\|\c
.B #pragma implementation\c
\&\|' by itself is equivalent to `\|\c
.B 
#pragma implementation "allclass.h"\c
\&\|'.  Use the string argument if you want a single implementation
file to include code from multiple header files.  

There is no way to split up the contents of a single header file into
multiple implementation files. 
.SH FILES
.ta \w'LIBDIR/g++\-include 'u
file.h	C header (preprocessor) file
.br
file.i	preprocessed C source file
.br
file.C	C++ source file
.br
file.cc	C++ source file
.br
file.cxx	C++ source file
.br
file.s	assembly language file
.br
file.o	object file
.br
a.out	link edited output
.br
\fITMPDIR\fR/cc\(**	temporary files
.br
\fILIBDIR\fR/cpp	preprocessor
.br
\fILIBDIR\fR/cc1plus	compiler
.br
\fILIBDIR\fR/collect	linker front end needed on some machines
.br
\fILIBDIR\fR/libgcc.a	GCC subroutine library
.br
/lib/crt[01n].o	start-up routine
.br
\fILIBDIR\fR/ccrt0	additional start-up routine for C++
.br
/lib/libc.a	standard C library, see
.IR intro (3)
.br
/usr/include	standard directory for 
.B #include
files
.br
\fILIBDIR\fR/include	standard gcc directory for
.B #include
files
.br
\fILIBDIR\fR/g++\-include	additional g++ directory for
.B #include
.sp
.I LIBDIR
is usually
.B /usr/local/lib/\c
.IR machine / version .
.br
.I TMPDIR
comes from the environment variable 
.B TMPDIR
(default
.B /usr/tmp
if available, else
.B /tmp\c
\&).
.SH "SEE ALSO"
gcc(1), cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1).
.br
.RB "`\|" gcc "\|', `\|" cpp \|', 
.RB `\| as \|', `\| ld \|',
and 
.RB `\| gdb \|'
entries in
.B info\c
\&.
.br
.I 
Using and Porting GNU CC (for version 2.0)\c
, Richard M. Stallman; 
.I
The C Preprocessor\c
, Richard M. Stallman;
.I 
Debugging with GDB: the GNU Source-Level Debugger\c
, Richard M. Stallman and Roland H. Pesch;
.I
Using as: the GNU Assembler\c
, Dean Elsner, Jay Fenlason & friends;
.I
gld: the GNU linker\c
, Steve Chamberlain and Roland Pesch.

.SH BUGS
For instructions on how to report bugs, see the GCC manual.

.SH COPYING
Copyright (c) 1991, 1992, 1993 Free Software Foundation, Inc.
.PP
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.
.PP
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.
.PP
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.