preprocessing by gcc

preprocessing by gcc

[PRASANTH RAJAGOPAL]

Hi,

I am using eclipse to cross compile for an embedded processor, using
its bare metal gcc tools (assembler, compiler, linker). The toolchains
are installed properly
and the toolchain calls the gcc tools and utils one by one. All works well.

I am trying to build a C project that also has a CRT.S file included
as the preprocessed file for startup.

I read the following:
Preprocessing - The *as* internal preprocessor:It does not do macro
processing, include file handling, or anything else you may get from
your C compiler's preprocessor.

Now the way the toolchains are used, it appears that .S files are
preprocessed by the Assembler, because my MACROs in the .S are never
getting defined & in the make files I see that the .S files are given
to Assembler. Without going inside eclipse, how can I let the pre
processing to be done by Compiler instead of Assembler?

Hope it make sense, being new to some of these things!

Thanks

Re: preprocessing by gcc

[PRASANTH RAJAGOPAL]

You are right. I ran the *.S through gcc and it worked. I then ran it
through gas and the MACROs were not defined and errors were thrown.

Wondering how I can make it work with Eclipse? They seem to have
locked *.S as an assembly source code & I am unable to remove the gas
from toolchain list.
I posted this in Eclipse forum, but have'n't got a reply yet.

Thanks

On Wed, Jun 1, 2011 at 1:44 AM, Andi Hellmund <mail@andihellmund.com> wrote:
> Hi
>>
>> I read the following:
>> Preprocessing - The *as* internal preprocessor:It does not do macro
>> processing, include file handling, or anything else you may get from
>> your C compiler's preprocessor.
>
> Yes, that's true. The preprocessor of GNU as is not a pre-processor in the
> sense of the C compiler.
>>
>> Now the way the toolchains are used, it appears that .S files are
>> preprocessed by the Assembler, because my MACROs in the .S are never
>> getting defined&  in the make files I see that the .S files are given
>> to Assembler.
>
> There is a "convention" that .s are pure assembler-files which could be
> passed to the assembler directly, but .S files do contain pre-processor
> macros (known from C). So, the .S must be passed to the pre-processor before
> passing the output to the assembler.
>
> The usual way is to NOT pass the .S file to 'as' but to pass it to 'gcc',
> e.g. gcc <file>.S -c. gcc will then do the steps as described above
> (preprocessor -> assembler).
>
> Best regards,
> Andi
>

Re: preprocessing by gcc

[David Paterson]

On Wed, Jun 1, 2011 at 6:33 AM, PRASANTH RAJAGOPAL
<prasanthris@gmail.com> wrote:
> You are right. I ran the *.S through gcc and it worked. I then ran it
> through gas and the MACROs were not defined and errors were thrown.
>
> Wondering how I can make it work with Eclipse? They seem to have
> locked *.S as an assembly source code & I am unable to remove the gas
> from toolchain list.
> I posted this in Eclipse forum, but have'n't got a reply yet.

You can either switch it for the individual file, or if you have
several .S files
in your project, do it for the whole project.

Open the properties for the file or project, select "C/C++ Build",
then "Settings",
"GCC Assembler", and simply change "as" to "gcc".  Easy as that :-)

Cheers,

David P.

Re: preprocessing by gcc

[PRASANTH RAJAGOPAL]

You are a saviour! I just kept playing around in Eclipse, and all
options broke one or the other thing, but this one is an easy
workaround.

Thanks

On Wed, Jun 1, 2011 at 1:42 PM, David Paterson <dnpaterson@gmail.com> wrote:
> On Wed, Jun 1, 2011 at 6:33 AM, PRASANTH RAJAGOPAL
> <prasanthris@gmail.com> wrote:
>> You are right. I ran the *.S through gcc and it worked. I then ran it
>> through gas and the MACROs were not defined and errors were thrown.
>>
>> Wondering how I can make it work with Eclipse? They seem to have
>> locked *.S as an assembly source code & I am unable to remove the gas
>> from toolchain list.
>> I posted this in Eclipse forum, but have'n't got a reply yet.
>
> You can either switch it for the individual file, or if you have
> several .S files
> in your project, do it for the whole project.
>
> Open the properties for the file or project, select "C/C++ Build",
> then "Settings",
> "GCC Assembler", and simply change "as" to "gcc".  Easy as that :-)
>
> Cheers,
>
> David P.
>