https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59568
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The simplest fix is just:
--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -495,6 +495,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Tp __re_x, __im_x;
_CharT __ch;
__is >> __ch;
+ if (!__is)
+ return __is;
if (__ch == '(')
{
__is >> __re_x >> __ch;
i.e. don't use putback if we didn't extract a character, so don't clear the
eofbit unless there's actually something to putback.
But the current implementation has other problems, like not doing a putback for
the character extracted when a ',' or ')' is not found.
This is closely related to https://wg21.link/lwg2714
