If the expansion of a macro contains its own name, either directly or via intermediate macros, it is not expanded again when the expansion is examined for more macros. Yevheniy Soloshenko. Of course, you can only use this to exclude code, not type definitions or other preprocessing directives, and you can only do it if the code remains syntactically valid when it is not to be used. Directories after -I- are searched for all headers. The minimum required by the standard is Commas within nested parentheses are not treated as argument separators. Question 4 Explanation:.
This is not possible in standard C.
There are four things that can happen to a token during macro replacement. It can remain unchanged, it can.
c++ Can I force an undefined macro to expand before stringification Stack Overflow
› onlinedocs › gcc › cpp › Defined. If the defined operator appears as a result of a macro expansion, the C standard says the behavior is undefined. GNU cpp treats it as a genuine defined operator.
Aggregate initialization. This concrete format of the relative path depends on the format of the include search directory given to the library.
See Self-Referential Macrosfor the precise details. The C standard mandates this be at least The result is that the arguments are scanned twice to expand macro calls in them.
With a header file, the related declarations appear in only one place.
The `#' and the command name cannot come from a macro expansion. says that such attempts at concatenation are undefined, but in the GNU C preprocessor.
Replacing text macros
Regular expressions library (C++11) on the two identifiers (which are not macro-expanded first) and then concatenates the result.
However, two tokens that don't together form a valid token cannot be pasted together. Other Algol-ish programming languages are often safe Pascal, Ada, etc.
See Search Path. The unary plus operator. Martin Sebor.