sgetn() fails to extract characters from an unbuffered stream
-------------------------------------------------------------
Key: STDCXX-1026
URL: https://issues.apache.org/jira/browse/STDCXX-1026
Project: C++ Standard Library
Issue Type: Bug
Components: 27. Input/Output
Affects Versions: 4.2.1
Reporter: Martin Sebor
Assignee: Martin Sebor
Fix For: 4.2.2
This bug was uncovered in this [discussion |
http://forums.sun.com/thread.jspa?messageID=10532349]:
{noformat}
$ cat t.cpp && make t && ./t
#include <cassert>
#include <istream>
#include <streambuf>
int main ()
{
static int x = '0';
struct: std::streambuf {
// unbuffered, always successfully reads one character
int_type underflow () { return x++; }
} sb;
// "endless" stream that never reaches EOF
std::istream endless (&sb);
char s [4] = "";
endless.read (s, sizeof s);
// expect to extract as many characters as requested
assert (endless.good ());
assert (sizeof s == endless.gcount ());
assert ('0' == s [0] && '1' == s [1] && '2' == s [2] && '3' == s [3]);
}
gcc -c -I/home/sebor/stdcxx-4.2.1/include/ansi \
-I/home/sebor/stdcxx-4.2.1/include \
-I/build/sebor/stdcxx-4.2.1-gcc-4.3.0-8D/include \
-I/home/sebor/stdcxx-4.2.1/examples/include \
-pedantic -nostdinc++ -O2 -W -Wall \
-Wcast-qual -Winline -Wshadow -Wwrite-strings -Wno-long-long
-Wcast-align t.cpp
t.cpp: In function 'int main()':
t.cpp:9: warning: inlining failed in call to 'virtual main()::<anonymous
struct>::~._26()': call is unlikely and code size would grow
t.cpp:24: warning: called from here
t.cpp:9: warning: inlining failed in call to 'virtual main()::<anonymous
struct>::~._26()': call is unlikely and code size would grow
t.cpp:24: warning: called from here
gcc t.o -o t -L/build/sebor/stdcxx-4.2.1-gcc-4.3.0-8D/lib
-Wl,-R/build/sebor/stdcxx-4.2.1-gcc-4.3.0-8D/lib -lstd8D -lsupc++ -lm
t: t.cpp:22: int main(): Assertion `endless.good ()' failed.
Aborted
{noformat}
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