[STDCXX-250] std::operator>>(istream&, string&) fails to set failbit after it extracts 0 characters

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 4.1.2, 4.1.3
• Fix Version/s: 4.2.1
• Component/s: 21. Strings

Environment

all

• Patch Info: Patch Available
• Severity: Incorrect Behavior
• Assignee: Farid Zaripov
• Reporter: Martin Sebor
• Created: 01/Jul/06 03:46
• Updated: 26/Feb/08 14:46
• Resolved: 19/Dec/07 15:45

Description

21.3.7.9, p3 says about the string extractor: "If the function extracts no characters, it calls is.setstate(ios::failbit), which may throw ios_base::failure (27.4.4.3)." The test program below shows that in unbuffered mode stdcxx fails to do so when an exception is thrown during the third call to underflow().

$ cat v.cpp && make v && ./v
#include <cassert>
#include <cstdio>
#include <istream>
#include <string>

int main ()
{
struct: std::streambuf {
int_type underflow ()

{ static int i = 0; // i == 0: sgect() invoked from sentry ctor // i == 1: sgetc() invoked from operator>>() // i == 2: sbumpc() invoked from operator>>() return 1 < i++ ? throw i : 'x'; }

} buf;

std::istream is (&buf);

std::string s;
is >> s;

std::printf ("state = %c%c%c, string = \"%s\" (length %u)\n",
is.rdstate () & is.badbit ? 'B' : '-',
is.rdstate () & is.eofbit ? 'E' : '-',
is.rdstate () & is.failbit ? 'F' : '-',
s.c_str (), s.size ());

assert ("x" == s);
assert ((is.failbit | is.badbit) == is.rdstate ());
}
gcc -c -I/build/sebor/dev/stdlib/include/ansi -D_RWSTDDEBUG -pthreads -D_RWSTD_USE_CONFIG -I/build/sebor/dev/stdlib/include -I/build/sebor/gcc-4.1.0-15s/include -I/build/sebor/dev/stdlib/../rwtest -I/build/sebor/dev/stdlib/../rwtest/include -I/build/sebor/dev/stdlib/tests/include -pedantic -nostdinc++ -g -W -Wall -Wcast-qual -Winline -Wshadow -Wwrite-strings -Wno-long-long v.cpp
gcc v.o -o v -L/build/sebor/gcc-4.1.0-15s/rwtest -lrwtest15s -pthreads -L/build/sebor/gcc-4.1.0-15s/lib -lstd15s -lsupc++ -lm
state = B--, string = "x" (length 1)
Assertion failed: (is.failbit | is.badbit) == is.rdstate (), file v.cpp, line 30
Abort (core dumped)