Claude output matching copyrighted StackOverflow code

I asked Claude to generate a C++ implementation of a base64 encoder, and the result was nearly identical to a version on StackOverflow. I guess that wouldn’t normally be an issue, except it turns out the StackOverflow example seems to be derived from copyrighted code.

Stackoverflow relevant comment: https://stackoverflow.com/questions/180947/base64-decode-snippet-in-c#comment137345692_13935718

Claude version:

std::string base64encode(const char* data, size_t length) { static const char* base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz" "0123456789+/";

std::string result; result.reserve(((length + 2) / 3) * 4); size_t i = 0; unsigned char char_array_3[3]; unsigned char char_array_4[4]; while (length--) { char_array_3[i++] = *(data++); if (i == 3) { char_array_4[0] = (char_array_3[0] & 0xfc) >> 2; char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4); char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6); char_array_4[3] = char_array_3[2] & 0x3f; for (i = 0; i < 4; i++) result += base64_chars[char_array_4[i]]; i = 0; } } if (i) { for (size_t j = i; j < 3; j++) char_array_3[j] = '\0'; char_array_4[0] = (char_array_3[0] & 0xfc) >> 2; char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4); char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6); for (size_t j = 0; j < i + 1; j++) result += base64_chars[char_array_4[j]]; while (i++ < 3) result += '='; } return result; }