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Update POD for Newx/Renew/Safefree vs libc analogs about heap corruption #22682

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Update POD for Newx/Renew/Safefree vs libc analogs about heap corruption #22682

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5 changes: 4 additions & 1 deletion pod/perlclib.pod
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,10 @@ should use C<sv_gets> instead:
p = realloc(p, n) Renew(p, n, t)

It is not portable to try to allocate 0 bytes; allocating 1 or more is
portable.
portable. Never pass pointers between C<Newx>, C<Renew>, C<Safefree> and
I<libc> equivalents C<malloc>, C<realloc>, C<free>. They are not from the
same memory pool or allocator. Either an instant or delayed I<SEGV> will
occur, or subtle memory leaks or subtle heap corruption.

memcpy(dst, src, n) Copy(src, dst, n, t)
memmove(dst, src, n) Move(src, dst, n, t)
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11 changes: 8 additions & 3 deletions pod/perldelta.pod
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Expand Up @@ -180,15 +180,20 @@ XXX Changes which significantly change existing files in F<pod/> go here.
However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
section.



Additionally, the following selected changes have been made:

=head3 L<XXX>
=head3 F<pod/perlguts.pod> and F<pod/perlclib.pod>

=over 4

=item *
=item Memory Allocation in C/XS

XXX Description of the change here
Documentation was updated to reflect that mixing C<Newx>, C<Renew>, and
C<Safefree> vs C<malloc>, C<realloc>, and C<free> not allowed, and mixing
pointers between the 2 classes of APIs is not allowed. Updates made in
F<pod/perlguts.pod> and F<pod/perlclib.pod>.

=back

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5 changes: 4 additions & 1 deletion pod/perlguts.pod
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Expand Up @@ -2384,7 +2384,10 @@ marked with correct flags.
All memory meant to be used with the Perl API functions should be manipulated
using the macros described in this section. The macros provide the necessary
transparency between differences in the actual malloc implementation that is
used within perl.
used within perl. Never pass pointers between C<Newx>, C<Renew>, C<Safefree>
and I<libc> equivalents C<malloc>, C<realloc>, C<free>. They are not from the
same memory pool or allocator. Either an instant or delayed I<SEGV> will
occur, or subtle memory leaks or subtle heap corruption.

The following three macros are used to initially allocate memory :

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