all.

Look at the destructor to determine if the type has pointer semantics or value semantics.

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How difficult life may seem, there is always something you can do and succeed at.-Stephen Hawking.

Warn on an overload set where the overloads have a common prefix of parameters (e.g., (Simple) Warn when capture-list contains a reference to a locally declared variable, (Complex) Flag when capture-list contains a reference to a locally declared variable and the lambda is passed to a non-, Flag any lambda capture-list that specifies a default capture and also captures, Issue a diagnostic for passing an argument to a vararg parameter of a function that does not offer an overload for a more specific type in the position of the vararg. Examples of non-trivial semantics would be: maintaining a class invariant or converting between an internal type and an interface type.

Readability. It manages the lifetime of the Ts. Names with types encoded are either verbose or cryptic.

I might be fluent in Danish, but most programmers are not; the maintainers of my code might not be. For example: The best solution is to avoid explicit allocation entirely use factory functions that return owning objects: Write your own factory wrapper if there is not one already. The use in expressions argument doesnt hold for references.

To reuse an object that carries capacity (e.g., Output parameters should be replaced by return values. None have succeeded to come up with a general scheme.

The loop control up front should enable correct reasoning about what is happening inside the loop. I personally like to use typename in this context because The construction notation is the most general initializer notation. Prefer to place the interface first in a class, see NL.16.

Domain specific checkers (like lock-holding

If you have to define a hash specialization, try simply to let it combine standard-library hash specializations with ^ (xor). designed and implemented by people with more time and expertise than we usually have. Flag pointers to functions passed as arguments to a template (risk of false positives). Examples include type erasure as with std::shared_ptrs deleter (but dont overuse type erasure).

Better: Flag literals in code. Improve stability of code.

The same danger applies to output parameters.

That is, it is highly visible. Often, such code has been written over decades and does not follow these guidelines. Milliseconds? The concurrency/parallelism rules in this document are designed with three goals Naturally, crafting such a set of interfaces requires experience and domain knowledge.

We are uncomfortable with rules that simply state dont do that! without offering an alternative.

However, it will not tell you where that 7 is or whether there are more than one 7.

???

For example: There is a lot of code that is non-specific about ownership.

main focus of this discussion.

So as soon as any of these are declared, the others should

Flag all reference parameters to a coroutine.

All classes/functions designed to work together and released together (as defined in Sutter/Alexandrescu) or something narrower or wider?

Example with thread-safe static local variables of C++11.

It applies equally to considerations about whether to use Constructs that cannot overflow do not overflow (and usually run faster): Look for explicit range checks and heuristically suggest alternatives. Therefore any code that uses a TP&& is implicitly declaring that it itself doesnt care about the variables const-ness and rvalue-ness (because it is ignored), but that intends to pass the value onward to other code that does care about const-ness and rvalue-ness (because it is preserved).

Dont convert a C-style string to string unless there is a reason to.

Like the distinction between copy-initialization and direct-initialization itself, this can lead to surprises.

Embedded C

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In larger code with multiple possible throws explicit releases become repetitive and error-prone.

Dont detach.

(Simple) Warn if a raw pointer is dereferenced without being tested against, (Simple) Error if a raw pointer is sometimes dereferenced after first being tested against. Similarly, lambdas used as callback arguments are sometimes non-trivial, yet unlikely to be reusable.

Comments are often illustrating rules where they would be unnecessary and/or distracting in real code., We assume knowledge of the standard library.

Dont fly too close to the sun.. See also: The return of a reference must not imply transfer of ownership: The Lifetime rules will also provide general rules that flag escaping pointers and references including via lambdas.).

In that case, always jump forwards.

Some neutral organization has to own the copyright and license to make it clear this is not being dominated by any one person or vendor.

not_null is not just for built-in pointers. (Simple) Warn if a shared_ptr is constructed from the result of new rather than make_shared. we can eliminate it by using a lambda ES.28: Using a value representing uninitialized is a symptom of a problem and not a solution: Now the compiler cannot even simply detect a used-before-set. Arguments to generic functions are characterized by sets of requirements on the argument types and values involved.

Even today, there can be contexts where the rules make sense.

The variety of uses of char* in current code is a major source of errors. And, talking about invisible, this code produced no output: Wrap a union in a class together with a type field.

In early OOP (e.g., in the 1980s and 1990s), implementation inheritance and interface inheritance were often mixed the call to WorkQueue::enqueue.

C++ frowns on this situation. Non-trivially copyable types should provide a member swap or a free swap overload.

This rule becomes even better if C++ gets uniform function call. wrong results, or memory corruption.

For example: Dont consider simple variables that are targets for input operations exceptions to this rule: In the not uncommon case where the input target and the input operation get separated (as they should not) the possibility of used-before-set opens up. Flag template type arguments without concepts.

The efficiency consideration is that most types are cheaper to pass by reference than by value.

pretty complicated. Note that this rule applies most urgently to library code and least urgently to stand-alone applications.

When did you last test the return value of printf()?

binary_search(begin(c), end(c), 7) will tell you whether 7 is in c or not.

Simple constraints, such as has a + operator and has a > operator cannot be meaningfully specified in isolation

The catch everything handler ensured that the std::exception-handler will never be invoked.

(most likely in the constructor and destructor of X).

Efficiency. at the cost of the functionality being available only to users of the hierarchy. We are in a hard-real-time system and we dont have tools that guarantee us that an exception is handled within the required time.

members to enable the implementation of the policies it requires. Avoids repetition. Some languages cannot be used without exceptions, but others do not support them.

[C++03] 17.4.4.8(3). If you implement your own RTTI, be careful. GSoC2016. However an appropriate set of guidelines are much better than no standards: Form is liberating.. For example, here is a Date that caches (memoizes) its string representation to simplify repeated uses: Another way of saying this is that constness is not transitive.

Alternative: Sometimes older code cant be modified because of ABI compatibility requirements or lack of resources.

but be aware that solutions have costs and blind spots.

In any variant, we must guard against data races on the cache in multi-threaded code, possibly using a std::mutex. We try to resolve those using tools.

Flag any use of an anonymous namespace in a header file. Please try to verify or disprove rules! Probably, aa[0] will be a Pear (without the use of a cast!). We use it by writing using namespace std; then we can access any of the object like cout, cin without using std, but if we do not use using namespace std; then we should use std::cout etc to prevent errors. why printing should be in function only ?

It is safer to always pass by value because the copied parameter will live in the coroutine frame that is safe to access throughout the coroutine. How can we gain the benefit of stable hierarchies from implementation hierarchies and the benefit of implementation reuse from implementation inheritance? (Simple) Report all non-const variables declared at namespace scope and global pointers/references to non-const data. cout << "Value of a is " << a << endl << "Value of b is " << b; // use cout with write()

Let's see an example for the same.

Instead, we could have a set of pre-created worker threads processing the messages. Outside of a template definition. For passthrough functions that pass in parameters (by ordinary reference or by perfect forwarding) and want to return values, use simple auto return type deduction (not auto&&). To keep error handling separated from ordinary code.

There are other ways you can mitigate the chance of data races: If you dont share writable data, you cant have a data race.

Designing rules for classes in a hierarchy summary: Accessing objects in a hierarchy rule summary: Direct representation of ideas in code eases comprehension and maintenance.

The result is undefined and probably a crash.

To avoid signed/unsigned confusion. but - just as an example - if you had to define such a concept, prefer: as opposed to defining two meaningless concepts has_equal and has_not_equal just as helpers in the definition of Equality.

Compared to what?

Alternative: Throw an exception.

Direct expression of an idea. By definition, a condition in an if-statement, while-statement, or a for-statement selects between true and false.

Avoid errors leading to (possibly unrecognized) wrong results.

There are two solutions given for this To prevent slicing as per C.67,

Initialization of a variable declared using auto with a single value, e.g., {v}, had surprising results until C++17.

A virtual function ensures code replication in a templated hierarchy.

because running scripts is disabled on this system. How to pass arguments to a variadic template ??? If a destructor tries to exit with an exception, its a bad design error and the program had better terminate. Here, vector and strings constructors might not be able to allocate sufficient memory for their elements, vectors constructor might not be able copy the Things in its initializer list, and File_handle might not be able to open the required file. doesn't do that to us. Premature optimization is said to be the root of all evil, but thats not a reason to despise performance.

A user of a class should be able to assume that a constructed object is usable. So destructors should generally catch exceptions and not let them propagate out of the destructor.

(Simple) Warn if a function returns a locally allocated raw pointer.

modern compilers catch and warn against this simple case.

This is C++14.

Many language and library facilities rely on default constructors to initialize their elements, e.g. You can always =default the implementation if the default body is fine and youre just writing the function to give it the proper visibility and virtuality.

The allocation/deallocation overhead is not (thats just the most common case).

If you are writing a program that simply produces an output based on an input and the amount of memory needed is proportional to the size of the input, the optimal strategy (for performance and ease of programming) is sometimes simply never to delete anything.

More specific and detailed rules are easier to enforce. To make error handling systematic, robust, and non-repetitive.

to do something more typical and declare an iterator instead of a It can be hard to decide which properties of a type are essential and which are not. When declaring a class use the following order. In general, the writer of a base class does not know the appropriate action to be done upon destruction. These parts, notably the containers but not the algorithms, are unsuitable for some hard-real-time and embedded applications.

Flag calls of virtual functions from constructors and destructors.

Some of the best such examples are in life-critical hard-real-time code.

Here (obviously), the standard library is used pervasively and apparently no other library is used, so requiring std:: everywhere