On 10/03/2015 06:47 AM, Jonathan Wakely wrote:
https://gcc.gnu.org/onlinedocs/gcc/Template-Instantiation.html
currently says that using -frepo "is your best option for application
code written for the Borland model, as it just works."
That was true at one point, but as can be seen from the mentions of
binutils 2.8 and Solaris 2, the information there is pretty old.
Since then -frepo has bitrotted occasionally, and it's much simpler to
rely on implicit instantiations in COMDAT sections, controlling
specific instantiations with explicit instantiations if needed (using
'extern template' which was standardised in C++11).
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51910#c2 for an
example of bitrot (now fixed) and people being persuaded by the docs
that -frepo is the best option.
So this revises the docs, to downplay the usefulness of -frepo,
and to endorse the "do nothing" model (with selective explicit
instantations as needed).
It also changes another mention of -frepo to use a different C++-only
option, to further de-emphasize -frepo.
OK for trunk?
Thanks for tackling this. I remember thinking that this section looked
bit-rotted when I was reviewing the manual earlier this year. Your
patch looks like a step in the right direction, but can I get you to fix
a couple other things while you're at it?
First, I think the reference to ancient ld versions is confusing, and it
would be better to rewrite that to emphasize that this is the default
behavior on most targets. (I'd guess that anybody trying to use a
recent GCC release with an ld version from 1996 is going to run into
more critical blocking issues than this one.) Maybe something like:
"G++ implements the Borland model on targets where the linker supports
it, including both ELF targets (such as GNU/Linux) and Microsoft
Windows. Otherwise G++ implements neither automatic model."
Second, if "Do nothing" is now the recommended way to handle this, let's
move that option to the front of the itemized list instead of the end.
Also, I'm confused by the "pretend" here; can we just delete that sentence?
-Sandra
