CMAKE_CXX_STANDARD_REQUIRED: 布尔变量,是否严格要求满足 c++标准 CMAKE_DEBUG_POSTFIX: debug 模式下会给生成的库赋予额外的后缀,便于区分,例如set(CMAKE_DEBUG_POSTFIX "_d") 鉴于MSVC 和 Linux 上的构建系统有太多不一样,CMake 直接定义了如下变量,可以直接判断并进入不同的处理分支 if(MSVC) # ... els...
-fstrong-eval-order Evaluate member access, array subscripting, and shift expressions in left-to- right order, and evaluate assignment in right-to-left order, as adopted for C++17. Enabled by default with -std=c++17. -fstrong-eval-order=some enables just the ordering of member access and ...
x=y; // Every expression is a statement int x; // Declarations are statements ; // Empty statement { // A block is a single statement int x; // Scope of x is from declaration to end of block } if (x) a; // If x is true (not 0), evaluate a else if (y) b; // If ...
Unary operators and assignment evaluate right to left. All others are left to right. Precedence does not affect order of evaluation, which is undefined. There are no run time checks for arrays out of bounds, invalid pointers, etc. T::X // Name X defined in class T N::X // Name X ...
In order to evaluate a comparison between two expressions we can use the relational and equality operators. The result of a relational operation is a Boolean value that can only be true or false, according to its Boolean result. We may want to compare two expressions, for example, to know ...
When it encounters a while loop construct, the compiler will use a standard coding pattern that lets it generate: • instructions that evaluate the expression to get a true or false result, • a "jump if false" conditional test that would set the program counter to the start of the ...
More generally, exceptions make the control flow of programs difficult to evaluate by looking at code: functions may return in places you don't expect. This causes maintainability and debugging difficulties. You can minimize this cost via some rules on how and where exceptions can be used, but...
constexpr: Evaluate at compile time (enable and ensure compile-time evaluation). const: Do not modify in this scope (specify immutability in interfaces). A constant expression must start out with an integral value, a floating point value, or an enumerator, and we can combine those using opera...
Default arguments are banned on virtual functions, where they don't work properly, and in cases where the specified default might not evaluate to the same value depending on when it was evaluated. (For example, don't write void f(int n = counter++);.) In some other cases, default argum...
x=y; // Every expression is a statement int x; // Declarations are statements ; // Empty statement { // A block is a single statement int x; // Scope of x is from declaration to end of block } if (x) a; // If x is true (not 0), evaluate a else if (y) b; // If ...