[Bug libstdc++/118455] The program crashes when synchronization with C-i/o is enabled; does not crash when it is disabled.

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118455

--- Comment #5 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to llualpu from comment #2)
> Yes, I usually use the simpler -D_GLIBCXX_DEBUG and -DDEBUG. But I'll take a
> look at -D_GLIBCXX_ASSERTIONS because this is the first time I hear about
> this. Thanks!

-D_GLIBCXX_DEBUG can catch the error.  -D_GLIBCXX_ASSERTIONS enables a subset
of checkings of -D_GLIBCXX_DEBUG, thus -D_GLIBCXX_DEBUG -D_GLIBCXX_ASSERTIONS
would be redundant.