bad() implies fail() but std::basic_ios::operator! is actually equivalent
to std::basic_ios::fail(), not bad().
For example,
std::ifstream is(argv[1]);
if (is.bad()) {
is probably wrong because, in case the file does not exist, only the failbit it set,
and not the badbit.
Other example:
double x;
is >> x;
If the stream 'is' does not contains a string that can represent a double,
then failbit is set (and maybe the eofbit if the stream is actually too
short), but not the badbit.
bad() can be used, in case fail() returned true, to discriminate between a
I/O error and a logical error.
See:
http://en.cppreference.com/w/cpp/io/basic_ios/operator_boolhttp://en.cppreference.com/w/cpp/io/ios_base/iostate
That is a followup-to my commit last year:
| ------------------------------------------------------------------------
| r63198 | lrineau | 2011-04-28 19:45:22 +0200 (Thu, 28 Apr 2011) | 5 lines
|
| Try to fix my last revision about cmake_policy, with CMake-2.6.x
|
| CMake gives an error if one tries to use cmake_policy(VERSION x.y.z) if
| x.y.z is greater than the current CMake version.
|
| ------------------------------------------------------------------------
The following check:
if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" VERSION_GREATER 2.6)
is useless just after a call to:
cmake_minimum_required(VERSION 2.6.2)
The script used to fix that was:
#!/usr/bin/env perl
$replacement=<<'END';
if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}.${CMAKE_PATCH_VERSION}" VERSION_GREATER 2.8.3)
cmake_policy(VERSION 2.8.4)
else()
cmake_policy(VERSION 2.6)
endif()
END
while(<>) {
if(/if\("\${CMAKE_MAJOR_VERSION}.\${CMAKE_MINOR_VERSION}" VERSION_GREATER 2.6\)/) {
while(<>) {
if(/^endif\(\)/) {
print "$replacement";
while(<>) {
print;
}
exit 0
}
}
}
print;
}
used. Those were mostly in Polyhedron and HalfedgeDS but some places
in Arrangement_2 used it, too. Neither of the parts of Arrangement_2
have been documented.
We declare
cmake_minimum_required(VERSION 2.6.2)
but we also use
cmake_policy(VERSION 2.8.4)
to declare that our CMake scripts are OK with all the defaults of CMake policies
as of CMake-2.8.4. That shuts down the warnings of CMake-2.8.4.
That way, we no longer need any declaration of specific policies.
Those two lines must be present and maintained in all our CMakeLists.txt
files (the one for the libraries, and also the one for examples and demos,
and maybe tests).
Sebastien Loriot
Andreas Fabri
Maxime Gimeno
Sébastien Loriot
Laurent Rineau
Laurent Rineau
Marc Glisse
Philipp Möller