What is Ifdef in makefile?
The ifdef directive begins the conditional, and specifies the condition. It contains single argument. If the given argument is true then condition becomes true. The ifndef directive begins the conditional, and specifies the condition.
What is IFEQ?
The ifeq directive begins the conditional, and specifies the condition. It contains two arguments, separated by a comma and surrounded by parentheses. Variable substitution is performed on both arguments and then they are compared.
How do I create a macro in makefile?
A macro definition line is a makefile line with a macro name, an equals sign “=”, and a macro value. In the makefile, expressions of the form $(name) or ${name} are replaced with value. If the macro name is a single letter, the parentheses or braces are optional (i.e. $X, $(X) and ${X} all mean “the value of macro X”).
What is a directive in makefile?
A directive is a command for make to do something special while reading the makefile. These include: Reading another makefile (see section Including Other Makefiles). Deciding (based on the values of variables) whether to use or ignore a part of the makefile (see section Conditional Parts of Makefiles).
What is in GNU make?
GNU Make is a tool which controls the generation of executables and other non-source files of a program from the program’s source files. Make gets its knowledge of how to build your program from a file called the makefile, which lists each of the non-source files and how to compute it from other files.
What are the parts of a makefile?
Makefiles contain five kinds of things: explicit rules, implicit rules, variable definitions, directives, and comments. Rules, variables, and directives are described at length in later chapters.
How do you comment in makefile?
‘ # ‘ in a line of a makefile starts a comment. It and the rest of the line are ignored, except that a trailing backslash not escaped by another backslash will continue the comment across multiple lines. A line containing just a comment (with perhaps spaces before it) is effectively blank, and is ignored.
What is wildcard in makefile?
3 The Function wildcard. $(wildcard pattern …) This string, used anywhere in a makefile, is replaced by a space-separated list of names of existing files that match one of the given file name patterns. If no existing file name matches a pattern, then that pattern is omitted from the output of the wildcard function.
