Exception on AccessViolation when trying to load library

Question

I am trying to load a library in my Delphi project and this library can be in two locations. So to load it, I am using the following code:

  try
    FHandle:=LoadLibrary(('some\address'));
  except on EAccessViolation do
    FHandle:=LoadLibrary(('another\address'));
  end;

however, I am having a problem because it never reaches the exception, I got the error that there was an Access Violation but it doesn't try to load from the other address...

does any one have an idea of the reasons?

thanks,

But what should I use to track this error and to have an exception to it? — Felipe, Sep 11 '13 at 13:29
If first LoadLibrary returns NULL (FHandle is NULL), call LoadLibrary again with another file name. — Alex F, Sep 11 '13 at 13:34
Why is this question protected? I believe @ChrisF has a good day — RBA, Sep 11 '13 at 18:10
@RBA - it was attracting spam answers (now deleted obviously). — ChrisF, Sep 11 '13 at 20:12
@ChrisF It seems that an awful lot of spam answers, on an awful lot of questions made it onto the site. I wonder if more could be done to block them at source. I mean, thanks for all the hard work dealing with them, but I'm sure you diamond mods would prefer to be doing other stuff. — David Heffernan, Sep 11 '13 at 22:38

score 4 · Accepted Answer · answered Sep 11 '13 at 13:38

LoadLibrary does not raise exceptions. It is a Win32 function. Consult the documentation and you will see that it returns NULL if it fails.

Your code should be:

FHandle := LoadLibrary('some\address');
if FHandle = 0 then
  FHandle := LoadLibrary('another\address');
if FHandle = 0 then
  // handle the error, probably by raising an exception

Another option might be to use FileExists to check which of your possible locations contains the file.

score 1 · Answer 2 · answered Sep 12 '13 at 11:36

To add to David's answer, if the function does return null i.e. failed, you can get the error with GetLastError(), see:

http://msdn.microsoft.com/en-us/library/ms679360.aspx

a list of error codes can be found here:

http://msdn.microsoft.com/en-us/library/ms679360.aspx

You can use the result from GetLastError to raise and exception yourself with a meaningfull exception type and description.

Exception on AccessViolation when trying to load library

2 Answers2