CodeSOD: Cancel Catch

"This WTF is in Matlab" almost feels like cheating. At one place I worked, somebody's job was struggling through a mountain of Matlab code and porting it into C. "This Matlab code looks like it was written by an alien," also doesn't really get much traction- all Matlab code looks like it was written by an alien. This falls into the realm of "Researchers use Matlab, researchers may be very smart about their domain, but generally don't know the first thing about writing maintainable code, because that's not their job."

But let's take a look at some MatLab Carl W found:

    try
        if (~isempty(fieldnames(bigStruct)) && isfield(bigStruct,'pathName'))
            [FileName, PathName] = uigetfile(bigStruct.pathName);
        else
            [FileName, PathName] = uigetfile(lastPath); %lastPath holds previous path
        end
    catch
        bigStruct = struct;
    end

The uigetfile function opens a file dialog box. When the user selects a file, FileName holds the filename, PathName holds the containing path. If the user doesn't select a valid file, or clicks "Cancel", both of those variables get set to 0. It's then up to the caller to check the return value and decide what happens next.

Which is not what happens here, obviously. The developer responsible seems to believe that it maybe throws an exception? And they can just catch it? Carl's best guess is that this is a "weird" way to catch the cancel button. But it does mean that FileName and PathName get set to 0, and those zeros propagate until something finally tries to open those files, at which point everything blows up and the user doesn't know why.

This post originally appeared on The Daily WTF.