C#•14mo ago

✅ CoTaskMemFree on a buffer returned by CsWin32

How do I do this?

9 Replies

$ask

MODiX•14mo ago

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Jester•14mo ago

just call CoTaskMemFree on that buffer? which api are you using that you need to do this?

reflectronic•14mo ago

(which, for what it's worth, is already available as https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.marshal.freecotaskmem?view=net-7.0)

Marshal.FreeCoTaskMem(IntPtr) Method (System.Runtime.InteropServices)

Frees a block of memory allocated by the unmanaged COM task memory allocator.

heftymouseOP•14mo ago

my code right now looks like this:

using System.Runtime.InteropServices;
using Windows.Win32;
using Windows.Win32.Foundation;
using Windows.Win32.UI.Shell;

PInvoke.SHCreateItemFromParsingName("shell:::{679f85cb-0220-4080-b29b-5540cc05aab6}", null, typeof(IShellItem).GUID, out var e);
IShellItem shellItem = e as IShellItem;
unsafe
{
    PWSTR pwstr;
    shellItem.GetDisplayName(SIGDN.SIGDN_NORMALDISPLAY, &pwstr);
    string thing = new string((char*)pwstr);
    Console.WriteLine(thing);
    // free pwstr here somehow?
}

using System.Runtime.InteropServices;
using Windows.Win32;
using Windows.Win32.Foundation;
using Windows.Win32.UI.Shell;

PInvoke.SHCreateItemFromParsingName("shell:::{679f85cb-0220-4080-b29b-5540cc05aab6}", null, typeof(IShellItem).GUID, out var e);
IShellItem shellItem = e as IShellItem;
unsafe
{
    PWSTR pwstr;
    shellItem.GetDisplayName(SIGDN.SIGDN_NORMALDISPLAY, &pwstr);
    string thing = new string((char*)pwstr);
    Console.WriteLine(thing);
    // free pwstr here somehow?
}

Marshal.FreeCoTaskMem dosn't accept the pointer to pwstr directly it seems, and trying to use CoTaskMemFree itself results in an access violation sorry for posting such a half-baked question

reflectronic•14mo ago

you don't pass the pointer to PWSTR to CoTaskMemFree you pass PWSTR itself Marshal.FreeCoTaskMem((nint)pwstr);

heftymouseOP•14mo ago

this complains about not being able to cast

reflectronic•14mo ago

(nint)pwstr.Value?

heftymouseOP•14mo ago

that worked, thanks a ton

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✅ CoTaskMemFree on a buffer returned by CsWin32