Why doesn't this work?

SPlatten

I am debugging a project where I know some of the pointers used are nullptr, so I originally implemented calls to Q_ASSERT_X before the usage, however the execution didn't stop even though the pointer is nullptr, so I tried replacing with assert, same behaviour.

assert(m_d!=nullptr);
return m_d->smManager;

With a breakpoint on the assert I can see that m_d is nullptr but it continues on as if nothing was wrong...

[Edit]
Qt Creator 4.12.4
Qt 5.12.2
GCC 8.5.0 20210514
Operating System Red Hat 8.5.0-10 64 bit

jsulm

@SPlatten Debug or release build?
If NDEBUG is defined assert will do nothing.

SPlatten

@jsulm , I will investigate, I am able to debug the project, is NDEBUG required in addition to this?

SPlatten

@jsulm I searched the entire project build and found this:

# Disable asserts if building in release mode
CONFIG(release, debug|release): DEFINES += NDEBUG

Does this explain it ?

jsulm

@SPlatten said in Why doesn't this work?:

Does this explain it ?

The question is: do you build in debug or release mode?
If in release mode then NDEBUG will be set.
You can also check compiler calls to see whether NDEBUG is set or not.

SPlatten

@jsulm , I believe I'm building in debug mode as I can debug the C++ and the source is visible.

SPlatten

@jsulm I commented out that line, cleaned the project and rebuilt, the behaviour is still the same.

jsulm

@SPlatten said in Why doesn't this work?:

I believe I'm building in debug mode

Why don't you simply check in which mode you're building?

SPlatten

@jsulm I know I'm building debug because I can debug, I start the process and attach using Qt Creator, I wouldn't be able to do that with source if I was running a process built for release.

JoeCFD

This line is actually not needed. But check if NDEBUG is used in your code explicitly.
CONFIG(release, debug|release): DEFINES += NDEBUG

if pro is used, you do not need to add anything for config. Maybe do not use mixed build "release | debug". Check the config setting in the .pro file.
if cmake is used, add
set( CMAKE_BUILD_TYPE Debug )

Q_ASSERT() works fine in my app.

SPlatten

@JoeCFD , I commented out this line from the Makefile. It was the only occurrence found, but still Q_ASSERT_X has no effect.

JonB

@SPlatten
If sounds like you are compiling such that assert/Q_ASSERT/Q_ASSERT_X are no-ops.

Alternatively your assumption that the pointer is null is wrong. For example there are other reasons that m_d->smManager could crash than m_d being nullptr.

There is no point guessing about compiler flags when you can just look at the compile command being executed very easily.

Since you are changing code anyway, replace the assert(m_d!=nullptr); with something you know how it behaves:

if (m_d == nullptr)
    QMessageBox() or write-to-file or whatever

JoeCFD

@SPlatten can you copy your Q_ASSERT_X code here? As JonB wrote, use your logger code to show if it is a nullptr.
Also open your Makefile in build dir and -g has to be there. If not, make distclean and rebuild your project.
CFLAGS = -pipe -g -Wall -Wextra -D_REENTRANT -fPIC $(DEFINES)
CXXFLAGS = -pipe -g -std=gnu++1z -Wall -Wextra -D_REENTRANT -fPIC $(DEFINES)

if you see -g and -O2 or -O3, that is mixed build.