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To solve this problem, it may be tempting to use the std::ios_base::width() method, but there still is a trap, as shown in this noncompliant code example:

#include <iostream>
 
void f() {
  char bufOne[12];
  char bufTwo[12];
  std::cin.width(12);
  std::cin >> bufOne;
  std::cin >> bufTwo;
}

In . In this example, the first read will not overflow, but the second read still could. The C++ Standard, [istream.extractors], paragraphs 7–9, describes the behavior of of operator>>(basic_istream &, charT *), and states in part part [ISO/IEC 14882-2014]:

operator>> then stores a null byte (charT()) in the next position, which may be the first position if no characters were extracted. operator>> then calls  then calls width(0).

Consequently, it is necessary to call call width() prior to each each operator>> call  call passing a bounded array.

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Noncompliant Code Example

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