[LLVMbugs] [Bug 17934] New: <iterator> C++14 cbegin/cend crbegin/crend definitions don't see all overloads of begin/end rbegin/rend

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17934

            Bug ID: 17934
           Summary: <iterator> C++14 cbegin/cend crbegin/crend definitions
                    don't see all overloads of begin/end rbegin/rend
           Product: libc++
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: hhinnant at apple.com
          Reporter: peter.sommerlad at hsr.ch
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11541
  --> http://llvm.org/bugs/attachment.cgi?id=11541&action=edit
corrected <iterator> file

when using cbegin/cend or crbegin/crend with arrays the code doesn't compile.
The reason is that the template definitions don't see all defined overloads of
the functions they rely upon. the array overloads of begin/end rbegin/rend come
later in the file <iostream>

Because we are on namespace level sequencing of function definitions is
important and a template function relying on another function must have all
relevant overloads visisble before the template definition.

Moving the overloads of begin/end rbegin/rend for arrays in front of the
definitions of cbegin/cend crbegin/crend respecitvely fixes this issue.

I'll attach a fixed <iterator>

Example code demonstrating the bug:
#include <iostream>
#include <iterator>

    using std::crbegin;
    using std::crend;
template <typename CONT>
void reverse_printer(CONT &&c){
    for (auto it=crbegin(c); it!=crend(c); ++it){
        std::cout << *it << ", ";
    }
    std::cout << '\n';
}

int main(){
    auto l={1,2,3,4,5};
    reverse_printer(l);
    int a[]={5,4,3,2,1};
    reverse_printer(a); // fails to compile
}

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