[PATCH v3 01/12] perf script: Make printing flags reliable

[Leo Yan]

On Mon, Mar 03, 2025 at 05:05:13PM +0200, Adrian Hunter wrote:

[...]

> >>> +	ret = max(ret, SAMPLE_FLAGS_STR_ALIGNED_SIZE);
> >>> +	return fprintf(fp, "  %-*s ", ret, str);
> >>
> >> -21 means the field width is 21 and left-justified.  It should not
> >> truncate the string.
> > 
> > No, it does not truncate the string.
> > 
> > It calculates a maximum value between the returned length and 21 (
> > defined in SAMPLE_FLAGS_STR_ALIGNED_SIZE).  It keeps left-justified and
> > can printing a complete string if the string length is bigger than 21.
> 
> Maybe I am missing something, but that isn't that what
> 
> 	return fprintf(fp, "  %-21s ", str);
> 
> does anyway?  Why change it to something more complicated.

You are right.  I should have done an experiment for this.

I will remove the max() sentence and update the last line:

        return fprintf(fp, "  %-*s ", SAMPLE_FLAGS_STR_ALIGNED_SIZE, str);

Another option is to drop this patch.  But I prefer to keep it, the
reason is except the benefit for the debugging log, an extra reason is
the SAMPLE_FLAGS_STR_ALIGNED_SIZE macro is used to replace the opened
value '21'.  The macro also will be used by a later patch for
right-alignment printing.  How about you think?

Thanks,
Leo