Re: [PATCH v2 1/2] Driver: Add new -truncate option

[Peter0x44 <peter0x44@disroot.org>]

18 Apr 2024 7:26:27 am Richard Biener <richard.guenther@gmail.com>:

> On Thu, Apr 18, 2024 at 6:12 AM Peter Damianov <peter0x44@disroot.org> 
> 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
>
> I suppose it should have been
>
> $ gcc hello.o -truncate hello.o
>
> in the example.

Correct.
Sorry about that.

>
>> $ 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.
>
> This looks good to me.
>
> Thanks,
> Richard.
>
>> Signed-off-by: Peter Damianov <peter0x44@disroot.org>
>> ---
>> v2: moved truncation to driver::final_actions
>> v2: moved handling of OPT_truncate to be in alphabetic order
>>
>> gcc/common.opt |  6 ++++++
>> gcc/gcc.cc     | 13 +++++++++++++
>> 2 files changed, 19 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..b4169bbd3be 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 +4542,10 @@ driver_handle_option (struct gcc_options *opts,
>>        do_save = false;
>>        break;
>>
>> +    case OPT_truncate:
>> +      totruncate_file = arg;
>> +      break;
>> +
>>      case OPT____:
>>        /* "-###"
>>          This is similar to -v except that there is no execution
>> @@ -9286,6 +9294,11 @@ 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
>>