Compile error "error: expected ';' at end of declaration list" using Catch testing framework in C++

Question

I'm trying to learn C++ by implementing some simple algorithms in it. In order to test these algorithms, I'd like to use Catch2. Here is a program I came up for binary search:

#define CATCH_CONFIG_MAIN
#include "catch.hpp"
#include <iostream>
using namespace std;

int binary_search_recursive(int A[], int key, int low, int high) {
    if (low > high) {
        return -1;
    }
    int mid = (low + high)/2;
    if (A[mid] == key) {
        return mid;
    } else if (key < A[mid]) {
        return binary_search_recursive(A, key, low, mid-1);
    } else {
        return binary_search_recursive(A, key, mid+1, high);
    }
}

int binary_search(int A[], int key, int len) {
  return binary_search_recursive(A, key, 0, len - 1);
}


// int main() {
//  int A[] = {1, 2, 4};
//  int key = 4;
//  int len = 3;
//  cout << binary_search(A, key, len);
//  return 0;
// }

TEST_CASE("Binary search works", "[binary_search]") {
    REQUIRE(1 == 1);
}

where I've copied the catch.hpp single header file into the same directory. The problem is that when I try to compile it using the g++ command on my Mac, I get the following error:

$ g++ BinarySearch.cpp
In file included from BinarySearch.cpp:2:
./catch.hpp:380:63: error: expected ';' at end of declaration list
        SourceLineInfo( char const* _file, std::size_t _line ) noexcept
                                                              ^
./catch.hpp:390:27: error: expected ';' at end of declaration list
        bool empty() const noexcept;
                          ^
./catch.hpp:391:63: error: expected ';' at end of declaration list
        bool operator == ( SourceLineInfo const& other ) const noexcept;
                                                              ^
./catch.hpp:392:62: error: expected ';' at end of declaration list
        bool operator < ( SourceLineInfo const& other ) const noexcept;
                                                             ^
./catch.hpp:496:16: error: unknown type name 'constexpr'
        static constexpr char const* const s_empty = "";
               ^
./catch.hpp:496:26: error: expected member name or ';' after declaration
      specifiers
        static constexpr char const* const s_empty = "";
        ~~~~~~~~~~~~~~~~ ^
./catch.hpp:499:20: error: expected ';' at end of declaration list
        StringRef() noexcept
                   ^
./catch.hpp:518:58: error: expected ';' at end of declaration list
        StringRef( char const* rawChars, size_type size ) noexcept
                                                         ^
./catch.hpp:542:38: error: expected ';' at end of declaration list
        void swap( StringRef& other ) noexcept;
                                     ^
./catch.hpp:545:9: error: 'auto' not allowed in function return type
        auto operator == ( StringRef const& other ) const noexcept -> bool;
        ^~~~
./catch.hpp:545:58: error: expected ';' at end of declaration list
        auto operator == ( StringRef const& other ) const noexcept -> bool;
                                                         ^
./catch.hpp:546:9: error: 'auto' not allowed in function return type
        auto operator != ( StringRef const& other ) const noexcept -> bool;
        ^~~~
./catch.hpp:546:58: error: expected ';' at end of declaration list
        auto operator != ( StringRef const& other ) const noexcept -> bool;
                                                         ^
./catch.hpp:548:9: error: 'auto' not allowed in function return type
        auto operator[] ( size_type index ) const noexcept -> char;
        ^~~~
./catch.hpp:548:50: error: expected ';' at end of declaration list
        auto operator[] ( size_type index ) const noexcept -> char;
                                                 ^
./catch.hpp:551:9: error: 'auto' not allowed in function return type
        auto empty() const noexcept -> bool {
        ^~~~
./catch.hpp:551:27: error: expected ';' at end of declaration list
        auto empty() const noexcept -> bool {
                          ^
./catch.hpp:559:9: error: 'auto' not allowed in function return type
        auto c_str() const -> char const*;
        ^~~~
./catch.hpp:559:27: error: expected ';' at end of declaration list
        auto c_str() const -> char const*;
                          ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

In short, the Catch2 source code itself is generating several of the same syntax error. I suspect that this might have to do with the 'version' of C++ Catch is written for is different from the one my compiler expects, but I wasn't able to quickly determine whether this was the issue from a Google search for this error.

Here are the details of my g++ compiler:

$ g++ -v
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.11.45.2)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Any idea what is causing this error, and how I could get the Catch2 unit tests to work?

Answer 1

I found the answer at https://github.com/catchorg/Catch2/issues/487. Apparently, you need to specify that the compiler should use C++11:

$ g++ -std=c++11 BinarySearch.cpp
$ ./a.out
===============================================================================
All tests passed (1 assertion in 1 test case)

In short, with the -std=c++11 option it works.