Zal.:.

Zal Walt

This story is about a bug generated by g++ and clang compilers (at least)
The condition_variables is a feature on the standard library of c++ (libstdc++), when its compiled statically a weird asm code is generated.

Any example on the link below will crash if its compiled statically:
https://en.cppreference.com/w/cpp/thread/condition_variable

In this case the condition_variable.wait() crashed, but this happens with other methods, a simple way to trigger it:

If this program is compiled dynamically the crash doesn't occur:

Looking the dissasembly there is a surprise created by the compiler:

Compilers:
g++ 9.2.1+20200130-2
clang++ v9

Both compilers are generating the "call 0x00"

If we check this call in a dynamic compiled:

The implementation of condition_variable in github:
https://github.com/gcc-mirror/gcc/blob/b7c9bd36eaacac42631b882dc67a6f0db94de21c/libstdc%2B%2B-v3/include/std/condition_variable

The compilers can't copile well this code in static, and same happens on other condition_variable methods.
I would say the _lock is being assembled improperly in static, is not exacly a null pointer derreference but the effects are the same, executing code at address 0x00 which on linux is a crash on most of cases.

More info

Zal Walt

Welcome to my another tutorial of PHP and MYSQL. In the previous tutorial I've briefly discussed How to make a PHP file and How to save the PHP file in the root directory of the server. How to run PHP script over the Web Browser etc.

Now in this tutorial I've discussed about inserting data into database by getting the values from user with the help of HTML form. One thing should be remembered that getting a values from users by HTML form is the only way to get values from users in PHP.

How To Insert Data into Database

Step 1:

Open your text editor and create HTML form.

Step 2:

Make a database connection in PHP.

Step 3:

Write an INSERT query for the sake of insertion data into database like INSERT INTO table_Name(table_Attribute1, table_Attribute2....) VALUES('1', 'Alex'...); etc. Now watch the video to make a better understanding the concept of insertion.

Zal.:.

6/05/2023

C++ Std::Condition_Variable Null Pointer Derreference

More info

How To Insert Data Into Database | Tutorial 3

How To Insert Data into Database

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