c++ - Unicode SQLDriverConnectW() : [unixODBC][Driver Manager]Data source name not found, 且未指定默认驱动程序

Question

下面是一个完整的ODBC程序。它所做的只是尝试使用完全限定的连接字符串打开与 SQLite 数据库的连接。我遇到的问题是，当启用 Unicode 时(使用 SQLDriverConnectW() 而不是 SQLDriverConnect())我得到错误:

libc++abi.dylib: terminating with uncaught exception of type database_error: connect: IM002: [unixODBC][Driver Manager]Data source name not found, and no default driver specified

我的 odbc.ini 文件是空的，下面是我的 odbcinst.ini 文件的内容:

[SQLite3]
Description=SQLite ODBC Driver
Driver=/usr/local/Cellar/sqliteodbc/0.9992/lib/libsqlite3odbc-0.9992.dylib
Setup=/usr/local/Cellar/sqliteodbc/0.9992/lib/libsqlite3odbc-0.9992.dylib
Threading=2

在代码的顶部有一个#if 1可以在Unicode和Non-Unicode之间切换代码(将其更改为#if 0以禁用Unicode) .当我启用 Unicode 时，出现错误。当我禁用 Unicode 时，它​​可以完美。知道为什么 Unicode 版本的连接找不到我的 DSN 吗？

/*

Build command:

clang++ -Wall -Werror \
    -std=c++14 -stdlib=libc++ \
    -I/usr/local/Cellar/unixodbc/2.3.2_1/include \
    -L/usr/local/Cellar/unixodbc/2.3.2_1/lib -lodbc \
    unittest.cpp && ./a.out

*/

#include <codecvt>
#include <sstream>
#include <stdexcept>
#include <string>
#include <vector>

#include <sql.h>
#include <sqlext.h>

#if 1
    // Enable Unicode
    #define STRING_LITERAL(s) L ## s
    #define CHAR SQLWCHAR
    #define ODBC_FUNCTION(f) f ## W
#else
    // Enable Non-unicode
    #define STRING_LITERAL(s) s
    #define CHAR SQLCHAR
    #define ODBC_FUNCTION(f) f
#endif

bool success(RETCODE rc);
void convert(const std::wstring& in, std::string& out);
void convert(const std::string& in, std::string& out);
template<typename T, std::size_t N> std::size_t arrlen(T(&)[N]);
std::string recent_error(SQLHANDLE handle, SQLSMALLINT handle_type, long &native, std::string &state);

class database_error : public std::runtime_error
{
public:
    database_error(void* handle, short handle_type, const std::string& info = "");
    const char* what() const noexcept { return message.c_str(); }
    const long native() const noexcept { return native_error; }
    const std::string state() const noexcept { return sql_state; }
private:
    long native_error;
    std::string sql_state;
    std::string message;
};

int main()
{
    RETCODE rc;

    HENV env;
    rc = SQLAllocHandle(
        SQL_HANDLE_ENV
        , SQL_NULL_HANDLE
        , &env);
    if(!success(rc))
        throw database_error(env, SQL_HANDLE_ENV, "env: ");

    rc = SQLSetEnvAttr(
        env
        , SQL_ATTR_ODBC_VERSION
        , (SQLPOINTER)SQL_OV_ODBC3
        , SQL_IS_UINTEGER);
    if(!success(rc))
        throw database_error(env, SQL_HANDLE_ENV, "version: ");

    HDBC conn;
    rc = SQLAllocHandle(
        SQL_HANDLE_DBC
        , env
        , &conn);
    if(!success(rc))
        throw database_error(env, SQL_HANDLE_ENV, "conn: ");

    CHAR dsn[1024];
    SQLSMALLINT dsn_size = 0;
    rc = ODBC_FUNCTION(SQLDriverConnect)(
        conn                                // ConnectionHandle
        , 0                                 // WindowHandle
        , (CHAR*)STRING_LITERAL("Driver=SQLite3;Database=nanodbc.db;") // InConnectionString
        , SQL_NTS                           // StringLength1
        , dsn                               // OutConnectionString
        , sizeof(dsn) / sizeof(CHAR)    // BufferLength
        , &dsn_size                         // StringLength2Ptr
        , SQL_DRIVER_NOPROMPT               // DriverCompletion
    );
    if(!success(rc))
        throw database_error(conn, SQL_HANDLE_DBC, "connect: ");
}

bool success(RETCODE rc)
{
    return rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO;
}

void convert(const std::wstring& in, std::string& out)
{
    out = std::wstring_convert<std::codecvt_utf8<wchar_t>>().to_bytes(in);
}

void convert(const std::string& in, std::string& out)
{
    out = in;
}

template<typename T, std::size_t N>
std::size_t arrlen(T(&)[N])
{
    return N;
}

std::string recent_error(
    SQLHANDLE handle
    , SQLSMALLINT handle_type
    , long &native
    , std::string &state)
{
    std::wstring result;
    std::string rvalue;
    std::vector<CHAR> sql_message(SQL_MAX_MESSAGE_LENGTH);
    sql_message[0] = '\0';

    SQLINTEGER i = 1;
    SQLINTEGER native_error;
    SQLSMALLINT total_bytes;
    CHAR sql_state[6];
    RETCODE rc;

    do
    {
        rc = ODBC_FUNCTION(SQLGetDiagRec)(
            handle_type
            , handle
            , (SQLSMALLINT)i
            , sql_state
            , &native_error
            , 0
            , 0
            , &total_bytes);

        if(success(rc) && total_bytes > 0)
            sql_message.resize(total_bytes + 1);

        if(rc == SQL_NO_DATA)
            break;

        rc = ODBC_FUNCTION(SQLGetDiagRec)(
            handle_type
            , handle
            , (SQLSMALLINT)i
            , sql_state
            , &native_error
            , sql_message.data()
            , (SQLSMALLINT)sql_message.size()
            , &total_bytes);

        if(!success(rc)) {
            convert(result, rvalue);
            return rvalue;
        }

        if(!result.empty())
            result += ' ';

        result += std::wstring(sql_message.begin(), sql_message.end());
        i++;

        // NOTE: unixODBC using PostgreSQL and SQLite drivers crash if you call SQLGetDiagRec()
        // more than once. So as a (terrible but the best possible) workaround just exit
        // this loop early on non-Windows systems.
        #ifndef _MSC_VER
            break;
        #endif
    } while(rc != SQL_NO_DATA);

    convert(result, rvalue);
    state = std::string(&sql_state[0], &sql_state[arrlen(sql_state) - 1]);
    native = native_error;
    std::string status = state;
    status += ": ";
    status += rvalue;

    // some drivers insert \0 into error messages for unknown reasons
    using std::replace;
    replace(status.begin(), status.end(), '\0', ' ');

    return status;
}

database_error::database_error(void* handle, short handle_type, const std::string& info)
: std::runtime_error(info), native_error(0), sql_state("00000")
{
    message = std::string(std::runtime_error::what()) + recent_error(handle, handle_type, native_error, sql_state);
}

我在 OS X 上编译。我已经通过 Homebrew 安装了 sqlite、sqliteodbc 和 unixodbc。我使用 clang 作为我的编译器。我用来编译和运行程序的命令位于源代码顶部的注释中。

Answer 1

Ben's mention of UTF-16-LE in his answer指出了解决此问题的途径。将字符串文字从 L"..." 更改为 u"..." 并保留类型转换为我解决了这个问题。如果没有转换，您仍然会收到错误:no known conversion from 'const char16_t [36]' to 'SQLWCHAR *' (aka 'unsigned short *')。