strVal confusingly gets executed during the "compilation" of the macro itself.
This means that the fooName argument doesn't yet have a value.
By using an if statement within the macro you're still doing the check during compile-time since everything in a macro happens on compile-time..
A C++ macro is defined as a section of code that can be replaced by that particular macro value.
The various types of C++ macros are Chain macros, Object-like macros, Function-like macros, and Multi-line macros.
The chain macros in C++ Macros are defined as macros inside the macros..
A macro is a piece of code in a program that is replaced by the value of the macro.
Macro is defined by #define directive.
Whenever a macro name is encountered by the compiler, it replaces the name with the definition of the macro..
Macros are used to make a sequence of computing instructions available to the programmer as a single program statement, making the programming task less tedious and less error-prone. (Thus, they are called "macros" because a "big" block of code can be expanded from a "small" sequence of characters.).
A compiler macro can be defined for a name that also names a function or macro.
That is, it is possible for a function name to name both a function and a compiler macro.
A function name names a compiler macro if compiler-macro-function is true of the function name in the lexical environment in which it appears..
Macros are used to make a sequence of computing instructions available to the programmer as a single program statement, making the programming task less tedious and less error-prone. (Thus, they are called "macros" because a "big" block of code can be expanded from a "small" sequence of characters.).
Macro Definition
A macro is a series of commands and actions that can be stored and run whenever you need to perform a computer task.
Use macros to automate actions that you perform repeatedly or on a regular basis.
Record the macro steps.
Build the macro with the editor.
No programming skills required..
The C preprocessor is a macro preprocessor (allows you to define macros) that transforms your program before it is compiled.
These transformations can be the inclusion of header files, macro expansions, etc..
Identifiers that represent statements or expressions are called macros.
In this preprocessor documentation, only the term "macro" is used.
When the name of a macro is recognized in the program source text, or in the arguments of certain other preprocessor commands, it's treated as a call to that macro..
A C++ macro is defined as a section of code that that particular macro value can replace.
We can define the macro by using a #define directive.
When the compiler goes to the macros while program compilation, the macro's name is replaced by the definition of the macro..
The macros in C are not stored in the memory.
Instead, the macros are called every time they are encountered in the code..
Speed versus size The main benefit of using macros is faster execution time.
During preprocessing, a macro is expanded (replaced by its definition) inline each time it's used.
A function definition occurs only once regardless of how many times it's called..
Some macros are defined only for specific build environments or compiler options.
Except where noted, the macros are defined throughout a translation unit as if they were specified as /D compiler option arguments.
When defined, the macros are expanded to the specified values by the preprocessor before compilation.
The compiler supports this predefined identifier specified by ISO C99 and ISO C++11. 1. __func__ The unqualified and unadorned name of the enclosing function as a function-local static const array of char.C++ void example(){ printf("%s\ ", __func__);} // prints "example"
The compiler supports these predefined macros specified by the ISO C99, C11, C17, and ISO C++17 standards. 1. __cplusplusDefined as an integer literal value when the translation unit is compiled as C++.
Otherwise, undefined. 2. __DATE__ The compilation date of the current source file.
The date is a constant length string literal of the form Mmm dd .
Several object-like macros are predefined; you use them without supplying their definitions.
They fall into three classes:
The standard predefined macros are specified by the C and/or C++ language standards, so they are available with all compilers that implement those standards.
Older compilers may not provide all of them.
Their names all start with double underscores.
This macro expands to the name of the current input file, in the form of a C string constant.
The macro is the integer literal value 201402L by default, or when the /std:c++14 compiler option is specified.
The macro is set to 201703L if the /std:c++17 compiler option is specified.
The macro is set to 202002L if the /std:c++20 compiler option is specified.
It's set to a higher, unspecified value when the /std:c++latest option is specified.
