[perl #134237] A Metaconfig probe for malloc_usable_size

# New Ticket Created by  Richard 
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Hi,

As mentioned on IRC, malloc_usable_size
(http://man7.org/linux/man-pages/man3/malloc_usable_size.3.html) seems
to be pretty common amongst Linux and BSD malloc implementations
nowadays. Metaconfig has a probe for the similar malloc_size on
Darwin, added in
https://perl5.git.perl.org/metaconfig.git/commit/83994881900edacd8c4e4d6534b1545554bb8274

Should a probe for malloc_usable_size should have its own file or be
appended to d_malloc_size.U due to the functional similarity?
Speculative patches are attached. (Once in, the intention is to add an
alternative definition to Perl_safesysmalloc_size.)

xenu pointed out that it would be useful to capture the minimum
allocation in a variable (e.g. MIN_MALLOC_SIZE). Where would be the
best place to do so?

Best Regards,
Richard

• [perl #134237] A Metaconfig probe for malloc_usable_size by Richard