Unzip buffer with large data length is crashing

This is the function I am using to unzip buffer.

string unzipBuffer(size_t decryptedLength, unsigned char * decryptedData)
{
    z_stream stream;
    stream.zalloc = Z_NULL;
    stream.zfree = Z_NULL;
    stream.avail_in = decryptedLength;
    stream.next_in = (Bytef *)decryptedData;
    stream.total_out = 0;
    stream.avail_out = 0;
    size_t dataLength = decryptedLength* 1.5;
    char c[dataLength];

    if (inflateInit2(&stream, 47) == Z_OK)
    {
        int status = Z_OK;
        while (status == Z_OK)
        {
            if (stream.total_out >= dataLength)
            {
                dataLength += decryptedLength * 0.5;
            }

            stream.next_out = (Bytef *)c + stream.total_out;

            stream.avail_out = (uint)(dataLength - stream.total_out);

            status = inflate (&stream, Z_SYNC_FLUSH);

        }
        if (inflateEnd(&stream) == Z_OK)
        {
            if (status == Z_STREAM_END)
            {
                dataLength = stream.total_out;
            }
        }
    }
    std::string decryptedContentStr(c, c + dataLength);
    return decryptedContentStr;
}

And it was working fine until today when I realized that it crashes with large data buffer (Ex: decryptedLength: 342792) on this line:

status = inflate (&stream, Z_SYNC_FLUSH);

after one or two iterations. Can anyone help me please?

via Chebli Mohamed