On 1/11/2021 12:51 PM, Ulrike Fischer wrote:
> pdftex will in texlive 2021 change  in two places
>
> 1. links where \pdfstartlink is in a different boxing level as
> \pdfendlink are no longer a fatal error but gives only a warning:
>
> x\hbox{\pdfstartlink
>      attr {/Border[0 0 1]}
>      user{
>          /Subtype/Link%
>          /A<<%
>           /Type/Action%
>           /S/URI%
>           /URI(blkub)%
>           >>%
>          } Linktext}
> \pdfendlink
>
> \bye
>
> pdfTeX warning: \pdfendlink ended up in different nesting level than
> \pdfstartl
> ink

hm, so bad nesting is not an error ... anyway

./pdf/pdflink.c     75:         normal_error("pdf backend","'endlink'
ended up in vlist");
./pdf/pdflink.c     79:         normal_error("pdf backend","'endlink'
ended up in different nesting level than 'startlink'");
./pdf/pdfthread.c    111:         normal_error("pdf backend",
"'endthread' ended up in hlist");
./pdf/pdfthread.c    113:         normal_error("pdf backend",
"'endthread' ended up in different nesting level than 'startthread'");

If we do that then threads also get a warning instead of an error and we
also won't be picky on a mode change. (So four cases where an error
becomes a warning.)