C builder 5 lean and mean compiler directive

#C BUILDER 5 LEAN AND MEAN COMPILER DIRECTIVE CODE#

#elif lets you create a compound conditional directive. That is, a variable name shouldn't be passed to a preprocessor directive, and a symbol can only be evaluated by a preprocessor directive. A symbol that you define with DefineConstants or with #define doesn't conflict with a variable of the same name. The scope of a symbol created with #define is the file in which it was defined. You can also define a symbol with the DefineConstants compiler option. By using the symbol as the expression passed to the #if directive, the expression evaluates to true.

#C BUILDER 5 LEAN AND MEAN COMPILER DIRECTIVE CODE#

Conditional compilation can be useful when compiling code for a debug build or when compiling for a specific configuration.Р”Р„ conditional directive beginning with an #if directive must explicitly be terminated with an #endif directive. #if, along with the #else, #elif, #endif, #define, and #undef directives, lets you include or exclude code based on the existence of one or more symbols. You can also group symbols and operators with parentheses. You can use the & (and), || (or), and ! (not) operators to evaluate whether multiple symbols have been defined. The statement #if DEBUG has the same meaning as #if (DEBUG = true). You can use the operators = (equality) and != (inequality) to test for the bool values true or false.

The #if statement in C# is Boolean and only tests whether the symbol has been defined or not. Unlike C and C++, you can't assign a numeric value to a symbol. When the C# compiler finds an #if directive, followed eventually by an #endif directive, it compiles the code between the directives only if the specified symbol is defined. #endif: Closes the preceding conditional compilation.#else: Closes the preceding conditional compilation and opens a new conditional compilation if the previous specified symbol isn't defined.

#elif: Closes the preceding conditional compilation and opens a new conditional compilation based on if the specified symbol is defined.

#if: Opens a conditional compilation, where code is compiled only if the specified symbol is defined.

You use four preprocessor directives to control conditional compilation:

#nullable restore warnings: Restores the nullable warning context to project settings.

#nullable enable warnings: Sets the nullable warning context to enabled.

#nullable disable warnings: Sets the nullable warning context to disabled.

#nullable restore annotations: Restores the nullable annotation context to project settings.

#nullable enable annotations: Sets the nullable annotation context to enabled.

#nullable disable annotations: Sets the nullable annotation context to disabled.

#nullable restore: Restores the nullable annotation and warning contexts to project settings.

#nullable enable: Sets the nullable annotation and warning contexts to enabled.

#nullable disable: Sets the nullable annotation and warning contexts to disabled.

The effect of the directives is as follows: A directive sets the context(s) it controls until another directive overrides it, or until the end of the source file. The #nullable directive controls the annotation and warning contexts and takes precedence over the project-level settings. Each context is either disabled or enabled.Р”В«oth contexts can be specified at the project level (outside of C# source code). This directive controls whether nullable annotations have effect, and whether nullability warnings are given.

The #nullable preprocessor directive sets the nullable annotation context and nullable warning context. A preprocessor directive must be the only instruction on a line. Unlike C and C++ directives, you can't use these directives to create macros. You use them to help in conditional compilation. Although the compiler doesn't have a separate preprocessor, the directives described in this section are processed as if there were one.

C builder 5 lean and mean compiler directive