arm-linux-gcc.1

arm-linux.rar

language supported by \s-1GCC\s0.
.PP
Here is a list of options that are \fIonly\fR for compiling \*(C+ programs:
.IP "\fB\-fabi\-version=\fR\fIn\fR" 4
.IX Item "-fabi-version=n"
Use version \fIn\fR of the \*(C+ \s-1ABI\s0.  Version 2 is the version of the
\&\*(C+ \s-1ABI\s0 that first appeared in G++ 3.4.  Version 1 is the version of
the \*(C+ \s-1ABI\s0 that first appeared in G++ 3.2.  Version 0 will always be
the version that conforms most closely to the \*(C+ \s-1ABI\s0 specification.
Therefore, the \s-1ABI\s0 obtained using version 0 will change as \s-1ABI\s0 bugs
are fixed.
.Sp
The default is version 2.
.IP "\fB\-fno\-access\-control\fR" 4
.IX Item "-fno-access-control"
Turn off all access checking.  This switch is mainly useful for working
around bugs in the access control code.
.IP "\fB\-fcheck\-new\fR" 4
.IX Item "-fcheck-new"
Check that the pointer returned by \f(CW\*(C`operator new\*(C'\fR is non-null
before attempting to modify the storage allocated.  This check is
normally unnecessary because the \*(C+ standard specifies that
\&\f(CW\*(C`operator new\*(C'\fR will only return \f(CW0\fR if it is declared
\&\fB\f(BIthrow()\fB\fR, in which case the compiler will always check the
return value even without this option.  In all other cases, when
\&\f(CW\*(C`operator new\*(C'\fR has a non-empty exception specification, memory
exhaustion is signalled by throwing \f(CW\*(C`std::bad_alloc\*(C'\fR.  See also
\&\fBnew (nothrow)\fR.
.IP "\fB\-fconserve\-space\fR" 4
.IX Item "-fconserve-space"
Put uninitialized or runtime-initialized global variables into the
common segment, as C does.  This saves space in the executable at the
cost of not diagnosing duplicate definitions.  If you compile with this
flag and your program mysteriously crashes after \f(CW\*(C`main()\*(C'\fR has
completed, you may have an object that is being destroyed twice because
two definitions were merged.
.Sp
This option is no longer useful on most targets, now that support has
been added for putting variables into \s-1BSS\s0 without making them common.
.IP "\fB\-fno\-const\-strings\fR" 4
.IX Item "-fno-const-strings"
Give string constants type \f(CW\*(C`char *\*(C'\fR instead of type \f(CW\*(C`const
char *\*(C'\fR.  By default, G++ uses type \f(CW\*(C`const char *\*(C'\fR as required by
the standard.  Even if you use \fB\-fno\-const\-strings\fR, you cannot
actually modify the value of a string constant, unless you also use
\&\fB\-fwritable\-strings\fR.
.Sp
This option might be removed in a future release of G++.  For maximum
portability, you should structure your code so that it works with
string constants that have type \f(CW\*(C`const char *\*(C'\fR.
.IP "\fB\-fno\-elide\-constructors\fR" 4
.IX Item "-fno-elide-constructors"
The \*(C+ standard allows an implementation to omit creating a temporary
which is only used to initialize another object of the same type.
Specifying this option disables that optimization, and forces G++ to
call the copy constructor in all cases.
.IP "\fB\-fno\-enforce\-eh\-specs\fR" 4
.IX 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 \fB\s-1NDEBUG\s0\fR.  The compiler
will still optimize based on the exception specifications.
.IP "\fB\-ffor\-scope\fR" 4
.IX Item "-ffor-scope"
.PD 0
.IP "\fB\-fno\-for\-scope\fR" 4
.IX Item "-fno-for-scope"
.PD
If \fB\-ffor\-scope\fR is specified, the scope of variables declared in
a \fIfor-init-statement\fR is limited to the \fBfor\fR loop itself,
as specified by the \*(C+ standard.
If \fB\-fno\-for\-scope\fR is specified, the scope of variables declared in
a \fIfor-init-statement\fR extends to the end of the enclosing scope,
as was the case in old versions of G++, and other (traditional)
implementations of \*(C+.
.Sp
The default if neither flag is given to follow the standard,
but to allow and give a warning for old-style code that would
otherwise be invalid, or have different behavior.
.IP "\fB\-fno\-gnu\-keywords\fR" 4
.IX Item "-fno-gnu-keywords"
Do not recognize \f(CW\*(C`typeof\*(C'\fR as a keyword, so that code can use this
word as an identifier.  You can use the keyword \f(CW\*(C`_\|_typeof_\|_\*(C'\fR instead.
\&\fB\-ansi\fR implies \fB\-fno\-gnu\-keywords\fR.
.IP "\fB\-fno\-implicit\-templates\fR" 4
.IX 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.
.IP "\fB\-fno\-implicit\-inline\-templates\fR" 4
.IX Item "-fno-implicit-inline-templates"
Don't emit code for implicit instantiations of inline templates, either.
The default is to handle inlines differently so that compiles with and
without optimization will need the same set of explicit instantiations.
.IP "\fB\-fno\-implement\-inlines\fR" 4
.IX Item "-fno-implement-inlines"
To save space, do not emit out-of-line copies of inline functions
controlled by \fB#pragma implementation\fR.  This will cause linker
errors if these functions are not inlined everywhere they are called.
.IP "\fB\-fms\-extensions\fR" 4
.IX Item "-fms-extensions"
Disable pedantic warnings about constructs used in \s-1MFC\s0, such as implicit
int and getting a pointer to member function via non-standard syntax.
.IP "\fB\-fno\-nonansi\-builtins\fR" 4
.IX Item "-fno-nonansi-builtins"
Disable built-in declarations of functions that are not mandated by
\&\s-1ANSI/ISO\s0 C.  These include \f(CW\*(C`ffs\*(C'\fR, \f(CW\*(C`alloca\*(C'\fR, \f(CW\*(C`_exit\*(C'\fR,
\&\f(CW\*(C`index\*(C'\fR, \f(CW\*(C`bzero\*(C'\fR, \f(CW\*(C`conjf\*(C'\fR, and other related functions.
.IP "\fB\-fno\-operator\-names\fR" 4
.IX Item "-fno-operator-names"
Do not treat the operator name keywords \f(CW\*(C`and\*(C'\fR, \f(CW\*(C`bitand\*(C'\fR,
\&\f(CW\*(C`bitor\*(C'\fR, \f(CW\*(C`compl\*(C'\fR, \f(CW\*(C`not\*(C'\fR, \f(CW\*(C`or\*(C'\fR and \f(CW\*(C`xor\*(C'\fR as
synonyms as keywords.
.IP "\fB\-fno\-optional\-diags\fR" 4
.IX Item "-fno-optional-diags"
Disable diagnostics that the standard says a compiler does not need to
issue.  Currently, the only such diagnostic issued by G++ is the one for
a name having multiple meanings within a class.
.IP "\fB\-fpermissive\fR" 4
.IX Item "-fpermissive"
Downgrade some diagnostics about nonconformant code from errors to
warnings.  Thus, using \fB\-fpermissive\fR will allow some
nonconforming code to compile.
.IP "\fB\-frepo\fR" 4
.IX Item "-frepo"
Enable automatic template instantiation at link time.  This option also
implies \fB\-fno\-implicit\-templates\fR.  
.IP "\fB\-fno\-rtti\fR" 4
.IX Item "-fno-rtti"
Disable generation of information about every class with virtual
functions for use by the \*(C+ runtime type identification features
(\fBdynamic_cast\fR and \fBtypeid\fR).  If you don't use those parts
of the language, you can save some space by using this flag.  Note that
exception handling uses the same information, but it will generate it as
needed.
.IP "\fB\-fstats\fR" 4
.IX Item "-fstats"
Emit statistics about front-end processing at the end of the compilation.
This information is generally only useful to the G++ development team.
.IP "\fB\-ftemplate\-depth\-\fR\fIn\fR" 4
.IX Item "-ftemplate-depth-n"
Set the maximum instantiation depth for template classes to \fIn\fR.
A limit on the template instantiation depth is needed to detect
endless recursions during template class instantiation.  \s-1ANSI/ISO\s0 \*(C+
conforming programs must not rely on a maximum depth greater than 17.
.IP "\fB\-fuse\-cxa\-atexit\fR" 4
.IX Item "-fuse-cxa-atexit"
Register destructors for objects with static storage duration with the
\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR function rather than the \f(CW\*(C`atexit\*(C'\fR function.
This option is required for fully standards-compliant handling of static
destructors, but will only work if your C library supports
\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR.
.IP "\fB\-fno\-weak\fR" 4
.IX Item "-fno-weak"
Do not use weak symbol support, even if it is provided by the linker.
By default, G++ will use weak symbols if they are available.  This
option exists only for testing, and should not be used by end\-users;
it will result in inferior code and has no benefits.  This option may
be removed in a future release of G++.
.IP "\fB\-nostdinc++\fR" 4
.IX Item "-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 the \*(C+ library.)
.PP
In addition, these optimization, warning, and code generation options
have meanings only for \*(C+ programs:
.IP "\fB\-fno\-default\-inline\fR" 4
.IX Item "-fno-default-inline"
Do not assume \fBinline\fR for functions defined inside a class scope.
  Note that these
functions will have linkage like inline functions; they just won't be
inlined by default.
.IP "\fB\-Wabi\fR (\*(C+ only)" 4
.IX Item "-Wabi ( only)"
Warn when G++ generates code that is probably not compatible with the
vendor-neutral \*(C+ \s-1ABI\s0.  Although an effort has been made to warn about
all such cases, there are probably some cases that are not warned about,
even though G++ is generating incompatible code.  There may also be
cases where warnings are emitted even though the code that is generated
will be compatible.
.Sp
You should rewrite your code to avoid these warnings if you are
concerned about the fact that code generated by G++ may not be binary
compatible with code generated by other compilers.
.Sp
The known incompatibilities at this point include:
.RS 4
.IP "\(bu" 4
Incorrect handling of tail-padding for bit\-fields.  G++ may attempt to
pack data into the same byte as a base class.  For example:
.Sp
.Vb 2
\&        struct A { virtual void f(); int f1 : 1; };
\&        struct B : public A { int f2 : 1; };
.Ve
.Sp
In this case, G++ will place \f(CW\*(C`B::f2\*(C'\fR into the same byte
as\f(CW\*(C`A::f1\*(C'\fR; other compilers will not.  You can avoid this problem
by explicitly padding \f(CW\*(C`A\*(C'\fR so that its size is a multiple of the
byte size on your platform; that will cause G++ and other compilers to
layout \f(CW\*(C`B\*(C'\fR identically.
.IP "\(bu" 4
Incorrect handling of tail-padding for virtual bases.  G++ does not use
tail padding when laying out virtual bases.  For example:
.Sp
.Vb 3
\&        struct A { virtual void f(); char c1; };
\&        struct B { B(); char c2; };
\&        struct C : public A, public virtual B {};
.Ve
.Sp
In this case, G++ will not place \f(CW\*(C`B\*(C'\fR into the tail-padding for
\&\f(CW\*(C`A\*(C'\fR; other compilers will.  You can avoid this problem by
explicitly padding \f(CW\*(C`A\*(C'\fR so that its size is a multiple of its
alignment (ignoring virtual base classes); that will cause G++ and other
compilers to layout \f(CW\*(C`C\*(C'\fR identically.
.IP "\(bu" 4
Incorrect handling of bit-fields with declared widths greater than that
of their underlying types, when the bit-fields appear in a union.  For
example:
.Sp
.Vb 1
\&        union U { int i : 4096; };
.Ve
.Sp
Assuming that an \f(CW\*(C`int\*(C'\fR does not have 4096 bits, G++ will make the
union too small by the number of bits in an \f(CW\*(C`int\*(C'\fR.
.IP "\(bu" 4
Empty classes can be placed at incorrect offsets.  For example:
.Sp
.Vb 1
\&        struct A {};
.Ve
.Sp
.Vb 4
\&        struct B {
\&          A a;
\&          virtual void f ();
\&        };
.Ve
.Sp
.Vb 1
\&        struct C : public B, public A {};
.Ve
.Sp
G++ will place the \f(CW\*(C`A\*(C'\fR base class of \f(CW\*(C`C\*(C'\fR at a nonzero offset;
it should be placed at offset zero.  G++ mistakenly believes that the
\&\f(CW\*(C`A\*(C'\fR data member of \f(CW\*(C`B\*(C'\fR is already at offset zero.
.IP "\(bu" 4
Names of template functions whose types involve \f(CW\*(C`typename\*(C'\fR or
template template parameters can be mangled incorrectly.
.Sp
.Vb 2
\&        template <typename Q>
\&        void f(typename Q::X) {}
.Ve
.Sp
.Vb 2
\&        template <template <typename> class Q>
\&        void f(typename Q<int>::X) {}
.Ve
.Sp
Instantiations of these templates may be mangled incorrectly.
.RE
.RS 4
.RE
.IP "\fB\-Wctor\-dtor\-privacy\fR (\*(C+ only)" 4
.IX Item "-Wctor-dtor-privacy ( only)"
Warn when a class seems unusable because all the constructors or
destructors in that class are private, and it has neither friends nor
public static member functions.
.IP "\fB\-Wnon\-virtual\-dtor\fR (\*(C+ only)" 4
.IX Item "-Wnon-virtual-dtor ( only)"
Warn when a class appears to be polymorphic, thereby requiring a virtual
destructor, yet it declares a non-virtual one.
This warning is enabled by \fB\-Wall\fR.
.IP "\fB\-Wreorder\fR (\*(C+ only)" 4
.IX Item "-Wreorder ( only)"
Warn when the order of member initializers given in the code does not
match the order in which they must be executed.  For instance:
.Sp
.Vb 5
\&        struct A {
\&          int i;
\&          int j;
\&          A(): j (0), i (1) { }
\&        };
.Ve
.Sp
The compiler will rearrange the member initializers for \fBi\fR
and \fBj\fR to match the declaration order of the members, emitting
a warning to that effect.  This warning is enabled by \fB\-Wall\fR.
.PP
The following \fB\-W...\fR options are not affected by \fB\-Wall\fR.
.IP "\fB\-Weffc++\fR (\*(C+ only)" 4
.IX Item "-Weffc++ ( only)"
Warn about violations of the following style guidelines from Scott Meyers'
\&\fIEffective