[v3,1/2] Driver: Add new -truncate option

This commit adds a new option to the driver that truncates one file after
linking.

Tested likeso:

$ gcc hello.c -c
$ du -h hello.o
4.0K  hello.o
$ gcc hello.o -truncate hello.o
$ ./a.out
Hello world
$ du -h hello.o
$ 0   hello.o

$ gcc hello.o -truncate
gcc: error: missing filename after '-truncate'

The motivation for adding this is PR110710. It is used by lto-wrapper to
truncate files in a shell-independent manner.

Signed-off-by: Peter Damianov <peter0x44@disroot.org>
---
 gcc/common.opt |  6 ++++++
 gcc/gcc.cc     | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

29 Apr 2024 12:16:26 am Peter Damianov <peter0x44@disroot.org>:

> This commit adds a new option to the driver that truncates one file 
> after
> linking.
>
> Tested likeso:
>
> $ gcc hello.c -c
> $ du -h hello.o
> 4.0K  hello.o
> $ gcc hello.o -truncate hello.o
> $ ./a.out
> Hello world
> $ du -h hello.o
> $ 0   hello.o
>
> $ gcc hello.o -truncate
> gcc: error: missing filename after '-truncate'
>
> The motivation for adding this is PR110710. It is used by lto-wrapper 
> to
> truncate files in a shell-independent manner.
>
> Signed-off-by: Peter Damianov <peter0x44@disroot.org>
> ---
> gcc/common.opt |  6 ++++++
> gcc/gcc.cc     | 14 ++++++++++++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index ad348844775..40cab3cb36a 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -422,6 +422,12 @@ Display target specific command line options 
> (including assembler and linker opt
> -time
> Driver Alias(time)
>
> +;; Truncate the file specified after linking.
> +;; This option is used by lto-wrapper to reduce the peak disk-usage 
> when
> +;; linking with many .LTRANS units.
> +truncate
> +Driver Separate Undocumented MissingArgError(missing filename after 
> %qs)
> +
> -verbose
> Driver Alias(v)
>
> diff --git a/gcc/gcc.cc b/gcc/gcc.cc
> index 728332b8153..830a4700a87 100644
> --- a/gcc/gcc.cc
> +++ b/gcc/gcc.cc
> @@ -2138,6 +2138,10 @@ static int have_E = 0;
> /* Pointer to output file name passed in with -o. */
> static const char *output_file = 0;
>
> +/* Pointer to input file name passed in with -truncate.
> +   This file should be truncated after linking. */
> +static const char *totruncate_file = 0;
> +
> /* This is the list of suffixes and codes (%g/%u/%U/%j) and the 
> associated
>     temp file.  If the HOST_BIT_BUCKET is used for %j, no entry is made 
> for
>     it here.  */
> @@ -4538,6 +4542,11 @@ driver_handle_option (struct gcc_options *opts,
>        do_save = false;
>        break;
>
> +    case OPT_truncate:
> +      totruncate_file = arg;
> +      do_save = false;
> +      break;
> +
>      case OPT____:
>        /* "-###"
>      This is similar to -v except that there is no execution
> @@ -9286,6 +9295,11 @@ driver::final_actions () const
>      delete_failure_queue ();
>    delete_temp_files ();
>
> +  if (totruncate_file != NULL && !seen_error ())
> +    /* Truncate file specified by -truncate.
> +       Used by lto-wrapper to reduce temporary disk-space usage. */
> +    truncate(totruncate_file, 0);
> +
>    if (print_help_list)
>      {
>        printf (("\nFor bug reporting instructions, please see:\n"));
> --
> 2.39.2
I resubmitted the patch because the previous one had a mistake.

It didn't set "do_save" to false, so it resulted in problems like this:

./gcc/xgcc -truncate
xgcc: error: missing filename after ‘-truncate’
xgcc: fatal error: no input files

./gcc/xgcc -truncate ??
xgcc: error: unrecognized command-line option ‘-truncate’
xgcc: fatal error: no input files

Therefore regressing some tests, and not working properly.
After fixing this, I ran all of the LTO tests again and observed no 
failures.

I'm not sure how I ever observed it working before, but I'm reasonably 
confident this is correct now.

On Mon, Apr 29, 2024 at 1:27 AM Peter0x44 <peter0x44@disroot.org> wrote:
>
> 29 Apr 2024 12:16:26 am Peter Damianov <peter0x44@disroot.org>:
>
> > This commit adds a new option to the driver that truncates one file
> > after
> > linking.
> >
> > Tested likeso:
> >
> > $ gcc hello.c -c
> > $ du -h hello.o
> > 4.0K  hello.o
> > $ gcc hello.o -truncate hello.o
> > $ ./a.out
> > Hello world
> > $ du -h hello.o
> > $ 0   hello.o
> >
> > $ gcc hello.o -truncate
> > gcc: error: missing filename after '-truncate'
> >
> > The motivation for adding this is PR110710. It is used by lto-wrapper
> > to
> > truncate files in a shell-independent manner.
> >
> > Signed-off-by: Peter Damianov <peter0x44@disroot.org>
> > ---
> > gcc/common.opt |  6 ++++++
> > gcc/gcc.cc     | 14 ++++++++++++++
> > 2 files changed, 20 insertions(+)
> >
> > diff --git a/gcc/common.opt b/gcc/common.opt
> > index ad348844775..40cab3cb36a 100644
> > --- a/gcc/common.opt
> > +++ b/gcc/common.opt
> > @@ -422,6 +422,12 @@ Display target specific command line options
> > (including assembler and linker opt
> > -time
> > Driver Alias(time)
> >
> > +;; Truncate the file specified after linking.
> > +;; This option is used by lto-wrapper to reduce the peak disk-usage
> > when
> > +;; linking with many .LTRANS units.
> > +truncate
> > +Driver Separate Undocumented MissingArgError(missing filename after
> > %qs)
> > +
> > -verbose
> > Driver Alias(v)
> >
> > diff --git a/gcc/gcc.cc b/gcc/gcc.cc
> > index 728332b8153..830a4700a87 100644
> > --- a/gcc/gcc.cc
> > +++ b/gcc/gcc.cc
> > @@ -2138,6 +2138,10 @@ static int have_E = 0;
> > /* Pointer to output file name passed in with -o. */
> > static const char *output_file = 0;
> >
> > +/* Pointer to input file name passed in with -truncate.
> > +   This file should be truncated after linking. */
> > +static const char *totruncate_file = 0;
> > +
> > /* This is the list of suffixes and codes (%g/%u/%U/%j) and the
> > associated
> >     temp file.  If the HOST_BIT_BUCKET is used for %j, no entry is made
> > for
> >     it here.  */
> > @@ -4538,6 +4542,11 @@ driver_handle_option (struct gcc_options *opts,
> >        do_save = false;
> >        break;
> >
> > +    case OPT_truncate:
> > +      totruncate_file = arg;
> > +      do_save = false;
> > +      break;
> > +
> >      case OPT____:
> >        /* "-###"
> >      This is similar to -v except that there is no execution
> > @@ -9286,6 +9295,11 @@ driver::final_actions () const
> >      delete_failure_queue ();
> >    delete_temp_files ();
> >
> > +  if (totruncate_file != NULL && !seen_error ())
> > +    /* Truncate file specified by -truncate.
> > +       Used by lto-wrapper to reduce temporary disk-space usage. */
> > +    truncate(totruncate_file, 0);
> > +
> >    if (print_help_list)
> >      {
> >        printf (("\nFor bug reporting instructions, please see:\n"));
> > --
> > 2.39.2
> I resubmitted the patch because the previous one had a mistake.
>
> It didn't set "do_save" to false, so it resulted in problems like this:
>
> ./gcc/xgcc -truncate
> xgcc: error: missing filename after ‘-truncate’
> xgcc: fatal error: no input files
>
> ./gcc/xgcc -truncate ??
> xgcc: error: unrecognized command-line option ‘-truncate’
> xgcc: fatal error: no input files
>
> Therefore regressing some tests, and not working properly.
> After fixing this, I ran all of the LTO tests again and observed no
> failures.
>
> I'm not sure how I ever observed it working before, but I'm reasonably
> confident this is correct now.

The series is still OK.  I suppose you do not have git write access so
I am testing the series with a LTO bootstrap and will push it once
that's successful.

Thanks,
Richard.