libstdc++/9661: cin.rdbuf()->sputbackc() does not put characters back to stdin
Tue Feb 11 12:56:00 GMT 2003
>Synopsis: cin.rdbuf()->sputbackc() does not put characters back to stdin
>Arrival-Date: Tue Feb 11 12:56:00 UTC 2003
Red Hat Linux 8.0
According to this posting to comp.lang.c++.moderated by Matt Austern:
cin.rdbuf()->sputbackc(c) and ungetc(c, stdin) should be equivalent and interchangable.
Although this is a QoI issue, it seems logical to fix this since
* cin.rdbuf()->sbumpc() and fgetc(stdin) are equivalent;
* characters returned by cin.rdbuf()->sgetc() can be consumed by both cin.rdbuf()->sbumpc() and fgetc(stdin)
* characters put back by ungetc will be returned by cin;
that is, cin.rdbuf()->sputbackc is the only case where the effect on cin and stdin differs.
Content-Type: text/plain; name="stdiosync.cc"
Content-Disposition: inline; filename="stdiosync.cc"
using namespace std;
int c1 = fgetc(stdin);
int c2 = cin.rdbuf()->sputbackc(c1);
assert(c2 == c1);
int c3 = fgetc(stdin);
assert(c3 == c1);
int c4 = cin.rdbuf()->sgetc();
assert(c4 == c3);
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