C# unsafe type -> char*[] , getting a pointer on char array

Question

Have:

[DllImport("OpenAL32.dll")]
static extern void alcOpenDevice(char*[] devicename);

Wanna send the name to this function like smth that:

char[] data = "Hello!".ToCharArray();
char*[] txt = &data;

But getting the errors:

cannot implicitly convert type char[] * to char * []

(funny error, because C# compiler refuses to define char[] * in /unsafe mode also :) )
Cannot take the address of, get the size of, or declare a pointer to a managed type (char[])

PS
When does char become managed? It's a struct, isn't it?

public struct Char : IComparable, IConvertible, IComparable<char>, IEquatable<char>

Although compiler showed info about declaring the pointer to a managed type (char[]). I can only suggest that when the type is an array CLR may present it like a managed type, but it sounds very crazy.

Aleksandr Dubinsky · Accepted Answer · 2012-12-29 22:46:51Z

6

alcOpenDevice does not take char*[] or char**, it takes char*, which you should specify as a string. It also returns a handle.

    [DllImport("OpenAL32.dll", CharSet = CharSet.Ansi)]
    static extern IntPtr alcOpenDevice(string devicename);

answered Dec 29, 2012 at 22:46

Aleksandr Dubinsky

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21 Comments

Icarus3 Over a year ago

Ahh, I got confuse for a while. "char*[]" ? is that even valid ?

Secret Over a year ago

char* is valid for C/C++; char* in C# is different stuff, it's not a pointer to char-array in C#, it's a pointer to a single char ( main different between C/C++ and C# definition of char* )

Aleksandr Dubinsky Over a year ago

@Icarus3 Yes, since the compiler accepts it. It is an array of char*. Use it to pass many char* to a function, by automatically marshalling the managed array to a char**

Aleksandr Dubinsky Over a year ago

@OlegOrlov That is not true. It can be a pointer to many chars. An int* can be a pointer to many ints. Just like C/C++. You can use fixed(int* intPointer = intArray)

Ben Voigt Over a year ago

C# char is not the same as C or C++ char (nevermind pointers or arrays).

|

Jens Eckervogt · Accepted Answer · 2024-05-19 09:00:27Z

0

If you use char[] to char*

You missed fixed statement:

char[] data = "Hello!".ToCharArray();
fixed (char* dataPtrs = data)
{
    // Logic here ...
}

I hope that my code helps you.

If you want to use char*[] from char** ( char Double Pointer ) - I will look for resolving...

answered May 19, 2024 at 9:00

Jens Eckervogt

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