https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65861
Bug ID: 65861
Summary: libstdc++ is silently generating wrong code when its
std::search is given an input iterator
Product: gcc
Version: 5.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: howarth.at.gcc at gmail dot com
While porting rstudio 0.98.1103 to build under clang/libc++, I uncovered a
defect in the libstdc++ handling of input iterators by std::search
(https://llvm.org/bugs/show_bug.cgi?id=23307). The reduced test case is
silently generating wrong code when its std::search is given an input iterator
(it assumes it can save the iterator position and backtrack).
#include <string>
#include <iterator>
#include <algorithm>
void f(std::istream &s, std::string x) {
std::istreambuf_iterator<char> eod;
std::search(std::istreambuf_iterator<char>(s),
eod,
x.begin(),
x.end());
}
Clang with libc++ properly rejects this with the error...
In file included from test3.cpp:1:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:439:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:628:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:604:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iterator:849:22:
error:
implicit instantiation of undefined template
'std::__1::basic_istream<char, std::__1::char_traits<char> >'
: __sbuf_(__s.rdbuf()) {}
^
test3.cpp:6:19: note: in instantiation of member function
'std::__1::istreambuf_iterator<char,
std::__1::char_traits<char> >::istreambuf_iterator' requested here
std::search(std::istreambuf_iterator<char>(s),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iosfwd:109:33:
note:
template is declared here
class _LIBCPP_TYPE_VIS_ONLY basic_istream;
^
In file included from test3.cpp:1:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:439:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:1572:12:
error:
no matching function for call to '__search'
return _VSTD::__search<typename
add_lvalue_reference<_BinaryPredicate>::type>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__config:358:15:
note:
expanded from macro '_VSTD'
#define _VSTD std::_LIBCPP_NAMESPACE
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:1586:19:
note:
in instantiation of function template specialization
'std::__1::search<std::__1::istreambuf_iterator<char,
std::__1::char_traits<char> >, std::__1::__wrap_iter<char *>,
std::__1::__equal_to<char, char> >' requested here
return _VSTD::search(__first1, __last1, __first2, __last2, __equal_to<__v1,
__v2>());
^
test3.cpp:6:12: note: in instantiation of function template specialization
'std::__1::search<std::__1::istreambuf_iterator<char,
std::__1::char_traits<char> >, std::__1::__wrap_iter<char *>
>' requested here
std::search(std::istreambuf_iterator<char>(s),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:1456:1:
note:
candidate function [with _BinaryPredicate = std::__1::__equal_to<char,
char> &, _RandomAccessIterator1 =
std::__1::istreambuf_iterator<char, std::__1::char_traits<char> >,
_RandomAccessIterator2 =
std::__1::__wrap_iter<char *>] not viable: no known conversion from
'typename
std::iterator_traits<istreambuf_iterator<char, char_traits<char> >
>::iterator_category'
(aka 'std::__1::input_iterator_tag') to
'std::__1::random_access_iterator_tag' for 6th argument
__search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:1419:1:
note:
candidate function [with _BinaryPredicate = std::__1::__equal_to<char,
char> &, _ForwardIterator1 =
std::__1::istreambuf_iterator<char, std::__1::char_traits<char> >,
_ForwardIterator2 = std::__1::__wrap_iter<char
*>] not viable: no known conversion from 'typename
std::iterator_traits<istreambuf_iterator<char, char_traits<char>
> >::iterator_category' (aka 'std::__1::input_iterator_tag') to
'std::__1::forward_iterator_tag' for 6th argument
__search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
^
2 errors generated.
