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Add diagnostics for min/max algorithms when a InputIterator is used. 

These algorithms require a ForwardIterator or better. Ensure
we diagnose the contract violation at compile time instead of
of silently doing the wrong thing.

Further algorithms will be audited in upcoming patches.

llvm-svn: 340426
This commit is contained in:
Eric Fiselier 2018-08-22 17:47:13 +00:00
parent b5686c4e4e
commit a60d7fac09
2 changed files with 43 additions and 0 deletions
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6
libcxx/include/algorithm
View File

@ -2398,6 +2398,8 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
_ForwardIterator _ForwardIterator
min_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) min_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
{ {
static_assert(__is_forward_iterator<_ForwardIterator>::value,
"std::min_element requires a ForwardIterator");
if (__first != __last) if (__first != __last)
{ {
_ForwardIterator __i = __first; _ForwardIterator __i = __first;
@ -2462,6 +2464,8 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
_ForwardIterator _ForwardIterator
max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
{ {
static_assert(__is_forward_iterator<_ForwardIterator>::value,
"std::max_element requires a ForwardIterator");
if (__first != __last) if (__first != __last)
{ {
_ForwardIterator __i = __first; _ForwardIterator __i = __first;
@ -2548,6 +2552,8 @@ _LIBCPP_CONSTEXPR_AFTER_CXX11
std::pair<_ForwardIterator, _ForwardIterator> std::pair<_ForwardIterator, _ForwardIterator>
minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
{ {
static_assert(__is_forward_iterator<_ForwardIterator>::value,
"std::minmax_element requires a ForwardIterator");
std::pair<_ForwardIterator, _ForwardIterator> __result(__first, __first); std::pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
if (__first != __last) if (__first != __last)
{ {

37
libcxx/test/std/algorithms/alg.sorting/alg.min.max/requires_forward_iterator.fail.cpp Normal file
View File

@ -0,0 +1,37 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// <algorithm>
// template<ForwardIterator Iter>
// max_element(Iter first, Iter last);
#include <algorithm>
#include <cassert>
#include "test_iterators.h"
int main() {
int arr[] = {1, 2, 3};
const int *b = std::begin(arr), *e = std::end(arr);
typedef input_iterator<const int*> Iter;
{
// expected-error@algorithm:* {{"std::min_element requires a ForwardIterator"}}
std::min_element(Iter(b), Iter(e));
}
{
// expected-error@algorithm:* {{"std::max_element requires a ForwardIterator"}}
std::max_element(Iter(b), Iter(e));
}
{
// expected-error@algorithm:* {{"std::minmax_element requires a ForwardIterator"}}
std::minmax_element(Iter(b), Iter(e));
}
}