In a way, this is plausible, as assigning a fresh string is a good situation to release memory back to the OS.

I'm not sure if pre-/resizing the buffer for a scalar still survives the various machinations. Obviously it breaks for sv_setpv, but I can see that breaking (fictional) code like the following:

    SV mysv = newSVpv("");
    SvGROW(mysv, 1024); // preallocate 1024 bytes as buffer for the re
+sponse
    sv_setpv("Hello World\0");
    some_systemcall_with_the_message_buffer( SvPV(mysv), 1024); // wri
+tes the response into mysv and expects 1024 bytes to be writable

[download]

... but I'm not sure if sv_setpv is supposed to copy the string or just copy the pointer to it.

If the threshold of 64 -> 16 bytes is sensible or if the resizing should only happen for larger decrements is to be seen.

In reply to Re: [XS] sv_setpv change in behaviour with perl-5.42.0 and later by Corion
in thread [XS] sv_setpv change in behaviour with perl-5.42.0 and later by syphilis

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.