Re: ref to read-only alias ... why?

[ikegami]

The condition in which "\" copies a scalar is: SvPADTMP(sv) && !IS_PADGV(sv). Not sure that that means. The condition is still there in the latest codebase.

It turns out that whether you get a read-only error or not depends on whether you are using a threaded Perl or not.

Using the lastest codebase:

$ git clean -dfx \
   && ./Configure -des -Dusedevel -Dcc='ccache cc' \
   && make miniperl
...

$ ./miniperl -le'for (1) { my $r = \$_; $$r++; print; print $$r; }'
Modification of a read-only value attempted at -e line 1.

$ git clean -dfx \
   && ./Configure -des -Dusedevel -Dcc='ccache cc' -Dusethreads \
   && make miniperl
...

$ ./miniperl -le'for (1) { my $r = \$_; $$r++; print; print $$r; }'
1
2