Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>AFAIK WinAPI callbacks (like window/dialog/thread procedures) must not propagate exceptions. This is because WinAPI internals (which call the callback) are not prepared to handle exceptions. They cannot be prepared because exceptions implementation is compiler specific while the code in WinAPI DLLs is fixed so it cannot handle all the possible exceptions propagation implementations.</p> <p>In some simple cases (especially when you compile with Visual Studio) you may observe that exceptions are propagated as would seem right. This is however a coincidence. And even if your application does not crash you are not sure if the WinAPI functions called in between did not allocate any resources which they did not released due to exception they were not prepared for.</p> <p>Additional layer of complexity is added by not knowing the source of the callback (in general – for some messages it can be deduced). Messages handled by your dialog procedure go through the message loop if and only if they were posted to your dialog. If they were sent then they skip the loop and are executed directly. Additionally if a message is sent then you don't know who sends the message – is it you? Or maybe Windows? Or some other window in other process trying to do something? (However this would be risky.) You don't know whether the calling site is prepared for an exception.</p> <p>Some way of workaround is offered by <a href="http://www.boost.org/doc/libs/1_39_0/libs/exception/doc/boost-exception.html" rel="nofollow noreferrer">Boost.Exception</a>. The library allows to somehow store the caught exception and use (in particular rethrow) it latter. This way you could wrap your dialog procedure in a <code>throw { ... } catch(...) { ... }</code> where in catch you would capture the exception and store it for latter use.</p> <p>EDIT: Since C++ 11 the features of <a href="http://www.boost.org/doc/libs/1_39_0/libs/exception/doc/boost-exception.html" rel="nofollow noreferrer">Boost.Exception</a> to store an exception object are part of the STD. You may use <code>std::exception_ptr</code> for that.</p> <p>However some problems still remain. You still have to recover somehow and return some value (for messages that require return value). And you would have to decide what to do with the stored exception. How to access it? Who will do it? What will he/she do with it?</p> <p>In case of <code>WM_INITDIALOG</code> you may pass arbitrary parameters to the dialog procedure with this message (use appropriate form of dialog creation function) and this could be a pointer to structure which will hold the stored exception (if any). Then you could investigate that structure to see if dialog initialization failed and how. This however cannot be applied simply to any message.</p>
    singulars
    1. This table or related slice is empty.
    1. POWin32 Message Handler Error Propagation
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USAdam Badura
    1. USAdam Badura
    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. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

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