GCC COMPILE OPTIONS

GCC COMPILE OPTIONS

[Lalit Seth]

Hi All,

I like to knw why we use "gmake bootstrap-lean" to compile GCC instead
of "gmake". How they are different and what behaviour changes are
there in 2 cases for GCC compiler.

Thanks
Lalit Seth

Re: GCC COMPILE OPTIONS

[Ian Lance Taylor]

"Lalit Seth" <sethlalitwo@gmail.com> writes:

> I like to knw why we use "gmake bootstrap-lean" to compile GCC instead
> of "gmake". How they are different and what behaviour changes are
> there in 2 cases for GCC compiler.

We have no idea why you do that.

The difference is that during bootstrap-lean old stages are removed
when they are no longer needed.  That is, bootstrap-lean uses less
disk space.  There is no difference in the compiler.

Ian

Re: GCC COMPILE OPTIONS

[Tim Prince]

Ian Lance Taylor wrote:
> "Lalit Seth" <sethlalitwo@gmail.com> writes:
> 
>> I like to knw why we use "gmake bootstrap-lean" to compile GCC instead
>> of "gmake". How they are different and what behaviour changes are
>> there in 2 cases for GCC compiler.
> 
> We have no idea why you do that.
> 
> The difference is that during bootstrap-lean old stages are removed
> when they are no longer needed.  That is, bootstrap-lean uses less
> disk space.  There is no difference in the compiler.
> 
I thought OP might be asking why it took so long for gcc build to 
implement a default which should know when bootstrap is required. Only 
the recent versions can build from scratch without explicit bootstrap 
option.

Re: GCC COMPILE OPTIONS

[Lalit Seth]

I have  experienced that GCC fails to compile with gmake but gets
successfully compiled when gmake bootstrap-lean is used. Why so. This
was on HPUX 11.11 for version 3.3.2

On 11/8/06, Tim Prince <timothyprince@sbcglobal.net> wrote:
> Ian Lance Taylor wrote:
> > "Lalit Seth" <sethlalitwo@gmail.com> writes:
> >
> >> I like to knw why we use "gmake bootstrap-lean" to compile GCC instead
> >> of "gmake". How they are different and what behaviour changes are
> >> there in 2 cases for GCC compiler.
> >
> > We have no idea why you do that.
> >
> > The difference is that during bootstrap-lean old stages are removed
> > when they are no longer needed.  That is, bootstrap-lean uses less
> > disk space.  There is no difference in the compiler.
> >
> I thought OP might be asking why it took so long for gcc build to
> implement a default which should know when bootstrap is required. Only
> the recent versions can build from scratch without explicit bootstrap
> option.
>

Re: GCC COMPILE OPTIONS

[Andrew Haley]

Please don't top-post.

Lalit Seth writes:
 > I have  experienced that GCC fails to compile with gmake but gets
 > successfully compiled when gmake bootstrap-lean is used. Why so.

Probably because your system compiler is broken.

 > This was on HPUX 11.11 for version 3.3.2
 > 
 > On 11/8/06, Tim Prince <timothyprince@sbcglobal.net> wrote:
 > > Ian Lance Taylor wrote:
 > > > "Lalit Seth" <sethlalitwo@gmail.com> writes:
 > > >
 > > >> I like to knw why we use "gmake bootstrap-lean" to compile GCC instead
 > > >> of "gmake". How they are different and what behaviour changes are
 > > >> there in 2 cases for GCC compiler.
 > > >
 > > > We have no idea why you do that.
 > > >
 > > > The difference is that during bootstrap-lean old stages are removed
 > > > when they are no longer needed.  That is, bootstrap-lean uses less
 > > > disk space.  There is no difference in the compiler.
 > > >
 > > I thought OP might be asking why it took so long for gcc build to
 > > implement a default which should know when bootstrap is required. Only
 > > the recent versions can build from scratch without explicit bootstrap
 > > option.
 > >

Re: gcc compile options

[Peter Kurpis]

> I have one more question regarding the creation of a
> shared library...
> 
> Should I use the g++ command with the -Wl options or
> can I use the ld command directly? Which one is
> better?

In general, I think  g++ -shared  is more convenient,
because it silently includes  libstdc++.so.* , for
instance.  But I think either can be used, although
to be honest, I've not used nor seen  ld  used to
build shared libs from c++ modules.

(When creating an executable,  gcc  and  g++  are even
more handy, since they link in the startup module 
(usually called something like  crt.o ), etcetera,
whereas with  ld , I think you'd have to be explicit
about these things.)

BTW, you may need to use  -fpic  when compiling source
code that you plan to link into a shared lib.

One way to see how things are commonly done on your
system is to examine native makefiles.  Besides looking
at them with an editor, you can also (with GNU make,
which you probably have on your system) do e.g.

	make -np | grep "^CPPFLAGS"

to see how  CPPFLAGS  is defined.  (The  -n  turns off
any actual building.)  Or, you can see how a particular
target would be build (again, without actually building
anything) with e.g.

	make -n mylib.so

assuming there's a target called  mylib.so .

Re: gcc compile options

[Peter Kurpis]

> have to do the following: compile multi-thread C++
> programs, generate an executable file and create a
> shared library with a list of exported external
> symbols of the shared object files. I need to do that
> in three distinct steps since I have to use a make
> file previously developed for use on AIX (VisualAge
> C++ compiler).
> 
> I'm thiinking of using the folowing commands
> ("make-like") to compile and create an executable
> file, but I don't know how to create shared libraries
> and export the symbols...
> 
> compile:
> gcc -x c++ -g -Iincdir -c srcdir/*.c objdir/*.o
> -mthreads

Use  g++  to compile c++ code, not  gcc -x c++ .  Also,
you need to use  -o  to specify the output file.

If you are writing a makefile, I would guess you just
need to specify the standard make variables, e.g.

CXX = g++
CPPFLAGS = -g -Iincdir

and use make's implicit rule for .cc files.

> create the executable:
> gcc -lsomelib -o execfile objfiles

The order of libs and objfiles matters, as the linker
only makes one pass through the command line resolving
symbols.  Ordinarily, libs resolve symbols in your
objfiles, so

g++ -o execfile objfiles -lsomelib

Note again the use of g++.  It has knowledge of what to
link against implicitly, a different set of things than 
gcc.

To create a shared library, since you are using the GNU
ld (inherently configured into gcc):

g++ -shared -o sharedlib objfiles

I haven't looked up whether you can create a list of 
exported symbols at link time -- you probably can, and 
you can pass the option to  ld  via
 -Wl,-xxx  where  xxx  is the option string.  (See  man ld
for the right thing.)  Alternatively, you can use  nm  
and  grep  to do the same thing.

gcc compile options

[Carla Nunes]

Hi!

I'm just getting started using the GCC compiler, and I
have to do the following: compile multi-thread C++
programs, generate an executable file and create a
shared library with a list of exported external
symbols of the shared object files. I need to do that
in three distinct steps since I have to use a make
file previously developed for use on AIX (VisualAge
C++ compiler).

I'm thiinking of using the folowing commands
("make-like") to compile and create an executable
file, but I don't know how to create shared libraries
and export the symbols...

compile:
gcc -x c++ -g -Iincdir -c srcdir/*.c objdir/*.o
-mthreads

-x c++ ---> c++ language
-g ---> to debug
-I ---> include directory
-c ---> to generate the .o files. do not link.
-mthreads ---> allows to handle with thread-safe
exception

create the executable:
gcc -lsomelib -o execfile objfiles

-lsomelib ---> i need to use some special libs

Any help will be welcome.

Thanks, Carla.

BTW, I'm using the GCC version 2.96-RH that comes with
Red Hat 7.1.




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Re: gcc compile options

[Alexandre Oliva]

On Jul  5, 2001, Carla Nunes <carlanunes@yahoo.com> wrote:

> compile:
> gcc -x c++ -g -Iincdir -c srcdir/*.c objdir/*.o -mthreads

Use g++ instead of gcc -x c++.

Note that it doesn't make sense to list object files when you use -c:
only source files can be listed.  In this case, you can use -o to
specify the output object file name, but then, you can only specify
one source file per compilation.

> gcc -lsomelib -o execfile objfiles

Always list libraries after object files they depend on.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me