Problems with string literals and etc.c.odbc.sql functions

[Fer22f via Digitalmars-d-learn]

By the use of this tutorial 
(http://www.easysoft.com/developer/languages/c/odbc_tutorial.html), I thought it would be very straightforward to use etc.c.odbc.sqlext and etc.c.odbc.sql to create a simple odbc application. But as soon as I started, I noticed a quirk:

     SQLRETURN ret;
     SQLHDBC dbc;
     ret = SQLDriverConnect(dbc, null, "DNS=*mydns*;", SQL_NTS,
             null, 0, null, SQL_DRIVER_COMPLETE);

This gives me an error: function 
etc.c.odbc.sqlext.SQLDriverConnect (void* hdbc, void* hwnd, char* 
szConnStrIn, short cbConnStrIn, char* szConnStrOut, short 
cbConnStrOutMax, short* pcbConnStrOut, ushort fDriverCompletion) 
is not callable using argument types (void*, typeof(null), 
string, int, typeof(null), int, typeof(null), int)

After some casting, I found out it's all related to the string 
literal. I thought it would work straight off the box, after 
reading the "Interfacing to C" spec 
(http://dlang.org/spec/interfaceToC.html).

When I remove the string literal and replace it with null, it 
compiles. .ptr and .toStringz both give immutable char* 
references, and don't work. A "cast(char *)"DNS=*maydns*;"" 
works, but it feels a lot like a hack that will not work in the 
long run.