https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72830
Bug ID: 72830
Summary: istream::seekg should not reset eofbit if -std=c++98
Product: gcc
Version: 4.6.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: alexhenrie24 at gmail dot com
Target Milestone: ---
Created attachment 39070
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39070&action=edit
Test program that demonstrates the problem
According to N3168 [1], as recently as 2010 the C++ standards did not permit
istream::seekg to reset istream::eof. When the change to the standard was
approved, libstdc++ started using the new behavior, even for programs compiled
with -std=c++98. This caused the bioinformatics program GERMLINE [2] to break.
In PEDIndividualsExtractor.cpp [3] we see:
void PEDIndividualsExtractor::loadInput()
{
...
while (!stream.eof() )
{
getIndividuals();
stream.seekg(numberOfMarkers*4 + 1,ios::cur);
}
...
}
void PEDIndividualsExtractor::getIndividuals()
{
string discard, ID, famID;
stream >> famID >> ID >> discard >> discard >> discard >> discard;
if(!stream.good()) return;
...
}
This code stopped working sometime between GCC 4.4.5 / libstdc++ 6.0.13 and GCC
4.6.3 / libstdc++ 6.0.16. With the change to libstdc++, stream.eof() is always
false, so loadInput() goes into an infinite loop. A simple test program is
attached.
I realize that I could petition the GERMLINE authors to change the loop
condition (and I eventually will), but the fact that you can't get the old
behavior even with -std=c++98 is a bug in GCC.
[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3168.htm
[2] http://www.cs.columbia.edu/~gusev/germline/
[3] http://www.cs.columbia.edu/~gusev/germline/germline-1-5-1.tar.gz
