245670 - nsEscapeHTML and co should use autosize allocation?

Status: RESOLVED WONTFIX

(Core :: XPCOM, enhancement)

Description

[Ben Bucksch (:BenB)]

Followup to bug 245399:

PRUnichar *resultBuffer = (PRUnichar
*)nsMemory::Alloc(aSourceBufferLen*7*sizeof(PRUnichar) +
sizeof(PRUnichar('\0')));

The 7 comes from the longest possible entity replacement. First, this is prone
to bugs - I *almost* caused a small buffer overflow (probably remotely
triggerably) here, because I didn't notice the hardcoding of the length (at first).

Also, this allocates 14 bytes memory per (unicode) source character for the
output string, although the vast majority needs only 2 bytes. This is not just
temporary, but returned to the called for further use. I don't know, how long
these strings are typically retained, but this may be a huge waste of memory,
depending on how often and long it's used.
<http://lxr.mozilla.org/seamonkey/search?string=nsEscapeHTML> says 'not often',
though.

Anyways, my suggestion is to use nsAutoString (or something like it) there,
which allocates memory (using nsMemory) based on actual need, and adopt the
buffer on return (so that it isn't |free|d).

Comment 1

[Ben Bucksch (:BenB)]

Ah, not many callers, don't care.