[Bug c++/100877] g++ freezes system by consuming infinite amount of memory

["StevenSun2021 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100877

--- Comment #1 from Steven Sun <StevenSun2021 at hotmail dot com> ---
I look at the call stack. Most of the time is wasted on `dump_template_parms`
in `gcc/cp/error.c`. I commented several functions calling it:

(I'm using stage-1 compiler)

`announce_function` in `gcc/toplev.c`
`push_tinst_level_loc` in `gcc/cp/pt.c`
`cp_printer` in `gcc/cp/error.c` (directly return true)

Then I got the output after a few seconds.

----------------------
examples/../include/./model.hpp: In instantiation of ‘’:
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:61:77:   required from ‘’
examples/../include/./model.hpp:55:147:   [ skipping 8 instantiation contexts,
use -ftemplate-backtrace-limit=0 to disable ]
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:55:147:   recursively required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:60:77:   required from ‘’
examples/../include/./model.hpp:60:77:   recursively required from ‘’
examples/../include/./model.hpp:55:147:   recursively required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:55:147:   recursively required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:60:77:   required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:382:55:   required from ‘’
examples/dcgan.cc:48:43:   required from here
examples/../include/./model.hpp:59:96: error: ‘’ has no member named ‘’
----------------------

But I cannot give the output. Because the dumping process will lead to an out
of memory.



If I disable member access check, it gives an error
---------------------
examples/../include/./model.hpp: In instantiation of ‘’:
examples/../include/./model.hpp:55:147:   recursively required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:60:77:   required from ‘’
examples/../include/./model.hpp:55:147:   required from ‘’
examples/../include/./model.hpp:382:55:   required from ‘’
examples/dcgan.cc:48:43:   required from here
examples/../include/./model.hpp:60:77: error: use of ‘’ before deduction of
‘auto’
--------------------
It's the same source location!

and it is in your definition of 
--------------------
 template< Expression Ex, Place_Holder Ph, Expression Ey >
  auto replace_placeholder_with_expression( Ex const& ex, Ph const&
old_place_holder, Ey const& new_expression )
--------------------