debug build - continue after Q_ASSERT (no abort)

kcris

Hi,

Is there a way to keep the Q_ASSERT in a debug build but without abort() ing the app when such an assert is hit?

Something like: ok, I see the error, now let's move on

Thanks

JonB

@kcris
There are a couple of ways. Partly depends on whether you have already written these Q_ASSERTs or are writing them now.

Easiest is probably to change to

if (!condition)
    qWarning("Message");    // or qWarning() << "Message";

You can always write a Q_WARNING() macro for this along the lines of the Q_ASSERT one.

If you are stuck with using Q_ASSERT you have a couple of choices:

Look at QtMessageHandler qInstallMessageHandler(QtMessageHandler handler), install your own, and change what it does in "fatal" case to not abort (see https://doc.qt.io/qt-5/qtglobal.html#qFatal).
Redefine Q_ASSERT macro for your desired behaviour.
IIRC, under some OSes at least, assert calls abort, and they allow you to redefine that that abort() actually does.

Really code should not have been written to use Q_ASSERT() where it would be safe to continue anyway. Assertions are for non-recoverable error conditions.

J.Hilk

@kcris said in debug build - continue after Q_ASSERT (no abort):

Hi,

Is there a way to keep the Q_ASSERT in a debug build but without abort() ing the app when such an assert is hit?

Something like: ok, I see the error, now let's move on

Thanks

Generally, no. The macro is designed to capture programming errors, not user or run-time errors, since it is generally disabled after a program exits its debugging phase

That said, Microsoft does its special soup again. So switch to MSVC and your asserts will behave as you describe it.

JonB

@kcris
There are a couple of ways. Partly depends on whether you have already written these Q_ASSERTs or are writing them now.

Easiest is probably to change to

if (!condition)
    qWarning("Message");    // or qWarning() << "Message";

You can always write a Q_WARNING() macro for this along the lines of the Q_ASSERT one.

If you are stuck with using Q_ASSERT you have a couple of choices:

Look at QtMessageHandler qInstallMessageHandler(QtMessageHandler handler), install your own, and change what it does in "fatal" case to not abort (see https://doc.qt.io/qt-5/qtglobal.html#qFatal).
Redefine Q_ASSERT macro for your desired behaviour.
IIRC, under some OSes at least, assert calls abort, and they allow you to redefine that that abort() actually does.

Really code should not have been written to use Q_ASSERT() where it would be safe to continue anyway. Assertions are for non-recoverable error conditions.

kcris

@J-Hilk
thanks.
Obviously I will not change the compiler because of the Q_ASSERT though.
Microsoft-ish soup or not, if somebody finds it useful, if there is a "market" for that, there is a reason...
I was just wondering if I missed some #define that might help

@JonB
nice ideas, both helpful. Thanks a lot

ps:
I ended up reinventing the wheel
which is what I did not want and hoped qt already provides in a portable way
I rolled my own QWARNING which does both a qWarning and a debug-break

KH-219Design

I, too, have reinvented this wheel.

I was "spoiled rotten" (on this axis, anyway) by using wxWidgets, which does imbue its assert macro with an optional "assert-then-continue" feature.

Here you can find my cobbled-together variation on this theme, which works on Linux and Windows. (it also worked on Mac a while back, but I haven't tested recently, and MacOSX has been changing at a fast pace.)