How to just print the output for -H without output anything else?

How to just print the output for -H without output anything else?

[Peng Yu]

Hi,

I just want to print the header information. Is there a way to
suppress the errors generated (Undefined symbols ...)? Thanks.

$ gcc -H -Iincdir main.c
. ./main.h
.. ./print.h
. incdir/print1.h
Undefined symbols for architecture x86_64:
  "_print", referenced from:
      _main in main-9c47c5.o
  "_print1", referenced from:
      _main in main-9c47c5.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)


==> main.c <==
// vim: set noexpandtab tabstop=2:

#include "main.h"
#include <print1.h>

int main() {
  print();
  print1();
}

==> print.c <==
#include <stdio.h>

void print() {
  puts("Hello World!");
}

==> incdir/print1.c <==
#include <stdio.h>

void print1() {
  puts("Hello World1!");
}

==> incdir/print1.h <==
// vim: set noexpandtab tabstop=2:

void print1();


-- 
Regards,
Peng

Re: How to just print the output for -H without output anything else?

[Xi Ruoyao]

On 2019-01-03 20:21 -0600, Peng Yu wrote:
> Hi,
> 
> I just want to print the header information. Is there a way to
> suppress the errors generated (Undefined symbols ...)? Thanks.
> 
> $ gcc -H -Iincdir main.c
> . ./main.h
> .. ./print.h
> . incdir/print1.h
> Undefined symbols for architecture x86_64:
>   "_print", referenced from:
>       _main in main-9c47c5.o
>   "_print1", referenced from:
>       _main in main-9c47c5.o
> ld: symbol(s) not found for architecture x86_64
> clang: error: linker command failed with exit code 1 (use -v to see invocation)

Hmmm... clang :).  Another off-topic thread caused by Apple Mac OS X.

A "-c" option would work.
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University

Re: How to just print the output for -H without output anything else?

[Peng Yu]

> A "-c" option would work.

This still generates the .o file. Is there an option that disable all
the side effect but just print the header info as -H?

-- 
Regards,
Peng

Re: How to just print the output for -H without output anything else?

[Xi Ruoyao]

On 2019-01-03 21:18 -0600, Peng Yu wrote:
> > A "-c" option would work.
> 
> This still generates the .o file. Is there an option that disable all
> the side effect but just print the header info as -H?

Maybe "-E -o /dev/null"?  Use "-E" instead of "-c" so the compiler and
assembler will not run, and "-o /dev/null" to throw the result
(preprocessed code).
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University

Re: How to just print the output for -H without output anything else?

[Alexander Monakov]

On Fri, 4 Jan 2019, Xi Ruoyao wrote:

> On 2019-01-03 21:18 -0600, Peng Yu wrote:
> > > A "-c" option would work.
> > 
> > This still generates the .o file. Is there an option that disable all
> > the side effect but just print the header info as -H?
> 
> Maybe "-E -o /dev/null"?  Use "-E" instead of "-c" so the compiler and
> assembler will not run, and "-o /dev/null" to throw the result
> (preprocessed code).

There's also -fsyntax-only, but it does more work compared to -E -o/dev/null.

Alexander

Re: How to just print the output for -H without output anything else?

[Peng Yu]

On Fri, Jan 4, 2019 at 12:42 AM Xi Ruoyao <xry111@mengyan1223.wang> wrote:
>
> On 2019-01-03 21:18 -0600, Peng Yu wrote:
> > > A "-c" option would work.
> >
> > This still generates the .o file. Is there an option that disable all
> > the side effect but just print the header info as -H?
>
> Maybe "-E -o /dev/null"?  Use "-E" instead of "-c" so the compiler and
> assembler will not run, and "-o /dev/null" to throw the result
> (preprocessed code).

Thanks. This works.

Is there a way to further strip off systems headers as in -MM? Thanks.

-- 
Regards,
Peng

Re: How to just print the output for -H without output anything else?

[Jonathan Wakely]

On Fri, 4 Jan 2019 at 15:26, Peng Yu <pengyu.ut@gmail.com> wrote:
>
> On Fri, Jan 4, 2019 at 12:42 AM Xi Ruoyao <xry111@mengyan1223.wang> wrote:
> >
> > On 2019-01-03 21:18 -0600, Peng Yu wrote:
> > > > A "-c" option would work.
> > >
> > > This still generates the .o file. Is there an option that disable all
> > > the side effect but just print the header info as -H?
> >
> > Maybe "-E -o /dev/null"?  Use "-E" instead of "-c" so the compiler and
> > assembler will not run, and "-o /dev/null" to throw the result
> > (preprocessed code).
>
> Thanks. This works.
>
> Is there a way to further strip off systems headers as in -MM? Thanks.

You're not using GCC, so maybe you should ask on a Clang list.

Re: How to just print the output for -H without output anything else?

[Peng Yu]

The options are the same for this purpose. I am just running the test
on Mac OS X. But I could use Linux as well. I don't think the results
are different.

On Fri, Jan 4, 2019 at 9:28 AM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>
> On Fri, 4 Jan 2019 at 15:26, Peng Yu <pengyu.ut@gmail.com> wrote:
> >
> > On Fri, Jan 4, 2019 at 12:42 AM Xi Ruoyao <xry111@mengyan1223.wang> wrote:
> > >
> > > On 2019-01-03 21:18 -0600, Peng Yu wrote:
> > > > > A "-c" option would work.
> > > >
> > > > This still generates the .o file. Is there an option that disable all
> > > > the side effect but just print the header info as -H?
> > >
> > > Maybe "-E -o /dev/null"?  Use "-E" instead of "-c" so the compiler and
> > > assembler will not run, and "-o /dev/null" to throw the result
> > > (preprocessed code).
> >
> > Thanks. This works.
> >
> > Is there a way to further strip off systems headers as in -MM? Thanks.
>
> You're not using GCC, so maybe you should ask on a Clang list.



-- 
Regards,
Peng

Re: How to just print the output for -H without output anything else?

[Jonathan Wakely]

On Fri, 4 Jan 2019 at 15:32, Peng Yu <pengyu.ut@gmail.com> wrote:
>
> The options are the same for this purpose. I am just running the test
> on Mac OS X. But I could use Linux as well. I don't think the results
> are different.

I don't care what OS you're using, I only care what compiler you're
using. You're not using GCC, you're using Clang pretending to be GCC.
That's still not GCC, it's Clang.

Re: How to just print the output for -H without output anything else?

[Peng Yu]

I am saying the default on Linux is gcc.

On Fri, Jan 4, 2019 at 9:33 AM Jonathan Wakely <jwakely.gcc@gmail.com>
wrote:

> On Fri, 4 Jan 2019 at 15:32, Peng Yu <pengyu.ut@gmail.com> wrote:
> >
> > The options are the same for this purpose. I am just running the test
> > on Mac OS X. But I could use Linux as well. I don't think the results
> > are different.
>
> I don't care what OS you're using, I only care what compiler you're
> using. You're not using GCC, you're using Clang pretending to be GCC.
> That's still not GCC, it's Clang.
>
-- 
Regards,
Peng