[Bug c++/79416] Internal compiler error for recursive template expansion

["jason at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79416

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P3
                 CC|                            |jason at gcc dot gnu.org
            Summary|[5/6/7 Regression] Internal |Internal compiler error for
                   |compiler error for          |recursive template
                   |recursive template          |expansion
                   |expansion                   |

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> ---
This is about running out of stack, instantiating a ridiculous number of
functions that call each other.  The error Martin sees in comment 1 is because
the old default instantiation limit of 500 was lower than the 800
instantiations the testcase wants to make of the 'nops' functions; since the
limit was raised to 900, we succeed in instantiating them, but then crash
running out of stack during ggc_collect.  Comment 2 demonstrates that we can
get the same crash on older GCC by lowering the number of instantiations the
testcase requires, so this really isn't a regression.

A simple fix for the crash would be to raise the stack limit; doubling the
amount requested in the call to stack_limit_increase from toplev::main (from
64MB to 128MB) allows the testcase to proceed.

A difficult fix for the crash would be to reduce the stack consumption of the
GGC machinery.