1. I had been detecting and trapping iterator == and \!= among iterators
in different containers as an error. But the trapping itself is actually
an error.
Consider:
#include <iostream>
#include <vector>
#include <algorithm>
template <class C>
void
display(const C& c)
{
std::cout << "{";
bool first = true;
for (const auto& x : c)
{
if (\!first)
std::cout << ", ";
first = false;
std::cout << x;
}
std::cout << "}\n";
}
int
main()
{
typedef std::vector<int> V;
V v1 = {1, 3, 5};
V v2 = {2, 4, 6};
display(v1);
display(v2);
V::iterator i = std::find(v1.begin(), v1.end(), 1);
V::iterator j = std::find(v2.begin(), v2.end(), 2);
if (*i == *j)
i = j; // perfectly legal
// ...
if (i \!= j) // the only way to check
v2.push_back(*i);
display(v1);
display(v2);
}
It is legal to assign an iterator from one container to another of the
same type. This is required to work. One might want to test whether or
not such an assignment had been made. The way one performs such a check
is using the iterator's ==, \!= operator. This is a logical and necessary
function and does not constitute an error.
2. I had a header circular dependence bug when _LIBCPP_DEBUG2 is defined.
This caused a problem in several of the libc++ tests.
Fixed.
3. There is a serious problem when _LIBCPP_DEBUG2=1 at the moment in that
std::basic_string is inoperable. std::basic_string uses __wrap_iterator
to implement its iterators. __wrap_iterator has been rigged up in debug
mode to support vector. But string hasn't been rigged up yet. This means
that one gets false positives when using std::string in debug mode. I've
upped std::string's priority in www/debug_mode.html.
llvm-svn: 187636
There are actually two debug modes:
1. -D_LIBCPP_DEBUG2 or -D_LIBCPP_DEBUG2=1
This is a relatively expensive debug mode, but very thorough. This is normally what you want to debug with, but may turn O(1) operations into O(N) operations.
2. -D_LIBCPP_DEBUG2=0
This is "debug lite." Only preconditions that can be checked with O(1) expense are checked. For example range checking on an indexing operation. But not iterator validity.
llvm-svn: 187369
unordered_set, however it is not complete yet for unordered_multiset,
unordered_map or unordered_multimap. There has been a lot of work done
for these other three containers, however that work was done just to
keep all of the tests passing.
You can try this out with -D_LIBCPP_DEBUG2. You will have to link to a
libc++.dylib that has been compiled with src/debug.cpp. So far, vector
(but not vector<bool>), list, and unordered_set are treated. I hope to
get the other three unordered containers up fairly quickly now that
unordered_set is done.
The flag _LIBCPP_DEBUG2 will eventually be changed to _LIBCPP_DEBUG, but
not today. This is my second effort at getting debug mode going for
libc++, and I'm not quite yet ready to throw all of the work under the
first attempt away.
The basic design is that all of the debug information is kept in a
central database, instead of in the containers. This has been done as
an attempt to have debug mode and non-debug mode be ABI compatible with
each other. There are some circumstances where if you construct a
container in an environment without debug mode and pass it into debug
mode, the checking will get confused and let you know with a readable
error message. Passing containers the other way: from debug mode out to
a non-debugging mode container should be 100% safe (at least that is the
goal).
llvm-svn: 186991
Marshall Clow