[Solved] QT error: error: undefined reference to ` VTable`

Question:

QT compilation error:

error: undefined reference to `vtable ...`

 

reason:

1.Qt uses signals and slots to implement communication features.
2.Signals and slots can be used when the class is derived from QObject and the Q_OBJECT macro is added to the header file.
3.When Q_OBJECT is added to the class header file QtCreator will automatically create a moc_***.cpp file that implements the code for signal and slot communication.
4.However, sometimes when we create a class through QtCreator without selecting the IDE option to derive it from the QObject class, but add it later, QtCreator will not automatically create the moc_***.cpp file. In this case it will report an error: undefined reference to `vtable for ***.

 

Solution:

According to various online methods, it can not be solved, nor can rebuild
mine is a small project. Just delete the build-XXX folder and rebuild it.

[Solved] Could not resolve placeholder ‘XXX‘ in value “${XXX}“

Problem overview:

The code is determined to be bug-free, but it cannot run after switching to a new environment or git from a remote warehouse.

Development environment:

IDEA

reason:

Because idea may have problems recognizing folder types. Especially when there are many switching spaces, GIT codes and new modules. We just need to set the folder type correctly.

Solution:

Set the Resources folder as a resource folder. If there are problems with other folders, the same is true.

After setting, the folder icon changes, indicating success.

[Solved] The Bean Validation API is on the classpath but no implementation could be found

Question

When starting the springboot service, the service reports an error. The specific error information is as follows:

Description:
The Bean Validation API is on the classpath but no implementation could be found
Action:
Add an implementation, such as Hibernate Validator, to the classpath

reason:

Dependency in POM

<dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>7.0.0.Final</version>
        </dependency>

And

<dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
            <version>2.2.6.RELEASE</version>
        </dependency>

Conflict.

Solution:

The dependency is deleted because it is not used in the service

<dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>7.0.0.Final</version>
        </dependency>

Restart the service normally.

VScode debug error: configured debug type ‘Python’ is not supported

When using vscode to debug, an error is reported in the pop-up window:

Configured debug type 'python' is not supported

Refer to the reference website: https://github.com/microsoft/vscode/issues/136712

The measured solution is metaphysical, as follows:

Delete Jupiter and python in vscope extensions, and then reinstall them; Close all vscodes; (this step is very important.) Open vscode again and you can debug normally.

[Solved] Asp.Net Core IIS Error: HTTP Error 500.30 – ASP.NET Core app failed to start

The error message prompts you to check whether there is an error message in the system event log

check the event log and find

according to ASP Net core module – Microsoft docs shows that the default configuration is in-process hosting, which is set to inprocess. It shows that the specified web project is out of process hosting

Solution:
only the published web Change hostingmodel = “inprocess” in config file to hostingmodel = “outofprocess” or delete hostingmodel = “inprocess” directly.

[Solved] MYSQL Start Project Error: this is incompatible with sql_mode=only_full_group_by

1. Error information

2. Edit file

# open the configuration file
vim /etc/my.cnf

# add this line in the end
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

3. Restart MySQL

systemctl restart mysqld

4. Test

# Start
nohup java -jar xxx.jar &

# Checnk the console
tail -f nohup.out

[Solved] Node sass version 7.0.0 is incompatible with ^ 4.0.0 | ^ 5.0.0 | ^ 6.0.0

Today, when writing the Vue page, according to the tutorial, I want to install sass-loader and node-sass, but when running the project after installation, the following errors are reported:

Node Sass version 7.0.0 is incompatible with ^4.0.0 || ^5.0.0 || ^6.0.0

The solution is as follows

Stop using node-sass and replace it with sass.

If you want to use SCSS or sass in your application, you need to do this:

First uninstall the previously installed node-sass 

yarn remove node-sass

If NPM is used, then

npm uninstall node-sass

Then install sass instead of node-sass 

yarn add -D sass

perhaps

npm i -D sass

Then your SCSS/sass file will be compiled correctly.

Vue3 Error: [vue/no-multiple-template-root] The template root requires exactly one element

vue3.0 supports <template/></template> tag to delegate more than one root element
Building the project with the latest Vite, the code in the default app.vue is as follows:

The code can run normally, but the vscode gives an error prompt:

[vue/no-multiple-template-root]
The template root requires exactly one element. eslint-plugin-vue

The reason is that the vetur plug-in has not been updated

The temporary solution is

Settings -> Search: eslint plugin Vue -> Uncheck the first (Vetur › Validation: Template )

Pycharm error: original error was: DLL load failed while importing _multiarray _Umath: the specified module could not be found

Anaconda is installed under the window system and the virtual environment is configured
everything runs normally using the command line, but an error is reported when running on pychram:
original error was: DLL load failed while importing _multiarray _umath

Tried:
1. Uninstall numpy and reinstall numpy
2. Add the python path again many times in the python settings

Final solution:
add system variables

after installing anaconda, only the first two are added, but not enough!!! \Bin and \library\bin should also be added!!!

Since it runs normally on the command line, the version problem between packages can be ignored. The problem must be the configuration of pycharm or system variables

Reference link: https://github.com/conda/conda/issues/7833

[Solved] MariaDB Add Datas Error: SQL error [1366] [22007]: (cIncorrect string value: ‘\xE5\xBC\xA0\xE4\xB8\x89’ for column

MariaDB add datas error:

SQL error [1366] [22007]: (conn=17) Incorrect string value: ‘\xE5\xBC\xA0\xE4\xB8\x89’ for column `SAOS`.`user`.`userName` at row 1

SQL:

INSERT into `user` values(1, "ZHANGSAN","123456");

The reason for this is the encoding problem. We can check the database character set encoding:

SHOW VARIABLES LIKE 'character%';

Variable_name                           |Value                       |
————————                +—————————-+
character_set_client                    |utf8mb4                     |
character_set_connection                |utf8mb4                     |
character_set_database                  |latin1                      |
character_set_filesystem                |binary                      |
character_set_results                   |utf8mb4                     |
character_set_server                    |latin1                      |
character_set_system                    |utf8                        |
character_sets_dir                      |/usr/share/mariadb/charsets/|

Above is the result displayed. You can see that there are two latin1 encodings. So to change the encoding, find the my.ini file at

whereis my.ini

The results are as follows:

my: /etc/my. cnf

That means this file replaces my Ini, we modify this file.

Add two lines of configuration:

default-character-set=utf8
character-set-server=utf8

Note that this file will tell you that it is read-only when it is modified. You should empower it:

sudo chmod 777  /etc/my.cnf

Then restart MariaDB.

systemctl restart mariadb.service

You need identity authentication. We can just enter the password.

Then view the database character set encoding:

In this way, insert the data just now, and the result is still an error. It seems that you need to continue to modify the configuration file.

[Solved] mmdetection benchmark.py Error: RuntimeError: Distributed package doesn‘t have NCCL built in

Cause:
use mmdetection’s tools/benchmark An error occurs when py calculates FPS
the error contents are as follows:

Traceback (most recent call last):
  File "tools/analysis_tools/benchmark.py", line 191, in <module>
    main()
  File "tools/analysis_tools/benchmark.py", line 183, in main
    init_dist(args.launcher, **cfg.dist_params)
  File "D:\Anaconda\envs\eagermot\lib\site-packages\mmcv\runner\dist_utils.py", line 18, in init_dist
    _init_dist_pytorch(backend, **kwargs)
  File "D:\Anaconda\envs\eagermot\lib\site-packages\mmcv\runner\dist_utils.py", line 32, in _init_dist_pytorch
    dist.init_process_group(backend=backend, **kwargs)
  File "D:\Anaconda\envs\eagermot\lib\site-packages\torch\distributed\distributed_c10d.py", line 510, in init_process_group
    timeout=timeout))
  File "D:\Anaconda\envs\eagermot\lib\site-packages\torch\distributed\distributed_c10d.py", line 597, in _new_process_group_helper
    raise RuntimeError("Distributed package doesn't have NCCL "
RuntimeError: Distributed package doesn't have NCCL built in

Cause analysis:
Windows does not support nccl backend

Solution:
1. Locate the following code location

File "D:\Anaconda\envs\eagermot\lib\site-packages\mmcv\runner\dist_utils.py", line 32, in _init_dist_pytorch

2. Add code before 1 (line 32)

backend='gloo'