Databases
StackOverflow2013
Postsdbo
POReceiving a char* from c++ into c#, and passing it back again
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POReceiving a char* from c++ into c#, and passing it back again
    primarykey
    data
    text
    <p>I'm having memory leak issues with a third party c++ dll. For certain calls, the dll allocates memory for the string, passes it out as a char* and then expects to receive that pointer back so that it can de-allocate the memory.</p> <p>Here are some comments from the header file, a couple of examples of where the char* get returned, and the signature of the "Release" method.</p> <p>(The dll is called SW_API, it's from a trade clearing house - if anyone has perhaps wrapped this already I'd love to talk to them!).</p> <pre><code> /* Strings returned by the API are similarly normal nul-terminated C strings. * The user should not attempt to change any of the bytes or read past the * terminating nul of any returned string. All returned strings must be * released using SW_ReleaseString() once the user is finished with the * result. Failure to do this will result in memory leaks. */ /** * @typedef const char* SW_XML * @brief A string containing an XML documents text. * @note As with all output strings, returned XML must be freed * by the user. See @ref resource. * @sa ErrorCodes */ typedef const char* SW_XML; const char* STDAPICALLTYPE SW_GetLastErrorSpecifics(); SW_ErrCode STDAPICALLTYPE SW_DealGetSWML(SW_LoginID lh, const char* swmlVersion, SW_DealVersionHandle dealVersionHandle, SW_XML* resultXML_out); void STDAPICALLTYPE SW_ReleaseString(const char* buffer); </code></pre> <p>Attempting to read up from various sources, I have tried the following:</p> <pre><code> // Extern declarations [DllImport(sw_api_dll, EntryPoint = "_SW_GetLastErrorSpecifics@0", CharSet = CharSet.Ansi)] public static extern IntPtr SW_GetLastErrorSpecifics(); [DllImport(sw_api_dll, EntryPoint = "_SW_DealGetSWML@16", CharSet = CharSet.Ansi)] public static extern int SW_DealGetSWML(int lh, string swmlVersion, string dealVersionHandle, [Out] out IntPtr outputSWML); [DllImport(sw_api_dll, EntryPoint = "_SW_ReleaseString@4", CharSet=CharSet.Ansi)] public static extern void SW_ReleaseString(IntPtr buffer); // Using the externs. private static string GetIntPtrStringAndRelease(IntPtr ptr) { string result = Marshal.PtrToStringAnsi(ptr); API.SW_ReleaseString(ptr); return result; } public static int SW_DealGetSWML(int lh, string swmlVersion, string dealVersionHandle, ref string outputSWML) { IntPtr outputSWML_out = new IntPtr(); int result = API.SW_DealGetSWML(lh, swmlVersion, dealVersionHandle, out outputSWML_out); outputSWML = GetIntPtrStringAndRelease(outputSWML_out); return result; } public static string SW_GetLastErrorSpecifics() { IntPtr ptr = API.SW_GetLastErrorSpecifics(); return GetIntPtrStringAndRelease(ptr); } </code></pre> <p>It seems I just can't get the API to release the strings.</p> <p>Now, it's possible that this is just a bug in the API, but I doubt it. More likely is I'm doing something funamentally wrong.</p> <p>All I know is that my working set just keeps on growing.</p> <p>The company in question provide a Java wrapper but won't stretch to a .Net wrapper.</p> <p>Any help most gratefully received.</p> <p>Brett.</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USBrett
    1. USBrett
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThis looks like a bug in the API to me. If the data you're getting back (i.e. the value returned from `GetIntPtrStringAndRelease` is good), then this should work.
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. USJim Mischel
    2. CO`GetIntPtrStringAndRelease` looks good to me.
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. USDavid Heffernan
    3. COThe value I get back is good. I almost wish it wasn't!
      singulars
      1. POReceiving a char* from c++ into c#, and passing it back again
      1. USBrett
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload