Re: [PATCH 1/2] Driver: Add new -truncate option

[Peter0x44 <peter0x44@disroot.org>]

On 2024-04-17 17:56, Peter Damianov wrote:
> 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
> $ ./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 |  5 +++++
>  gcc/gcc.cc     | 13 +++++++++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/gcc/common.opt b/gcc/common.opt
> index ad348844775..3ede2fa8552 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -422,6 +422,11 @@ 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 when 
> linking with
> +;; many .LTRANS units.
> +Driver Separate Undocumented MissingArgError(missing filename after 
> %qs)
> +
>  -verbose
>  Driver Alias(v)
> 
> diff --git a/gcc/gcc.cc b/gcc/gcc.cc
> index 728332b8153..00017964295 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.  */
> @@ -4607,6 +4611,10 @@ driver_handle_option (struct gcc_options *opts,
>        save_switch ("-o", 1, &arg, validated, true);
>        return true;
> 
> +    case OPT_truncate:
> +      totruncate_file = arg;
> +      break;
> +
>      case OPT_pie:
>  #ifdef ENABLE_DEFAULT_PIE
>        /* -pie is turned on by default.  */
> @@ -9273,6 +9281,11 @@ driver::maybe_run_linker (const char *argv0) 
> const
>  	       option).  */
>  	    error ("%s: linker input file not found: %m", outfiles[i]);
>  	}
> +
> +  if (totruncate_file != NULL && linker_was_run && !seen_error ())
> +    /* Truncate file specified by -truncate.
> +       Used by lto-wrapper to reduce temporary disk-space usage. */
> +    truncate(totruncate_file, 0);
On second thought, doing the truncation in driver::maybe_run_linker() 
seems wrong.
driver::final_actions seems like the better place to put this code.
Will resubmit.
>  }
> 
>  /* The end of "main".  */