What does IFEQ mean?
What does IFEQ mean?
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 you write if condition in makefile?
A comment starting with ‘ # ‘ may appear at the end of the line. Conditionals affect which lines of the makefile make uses. If the condition is true, make reads the lines of the text-if-true as part of the makefile; if the condition is false, make ignores those lines completely.
What is Ifndef in makefile?
The ifndef directive begins the conditional, and specifies the condition. It contains single argument. If the given argument is false then condition becomes true. The else directive causes the following lines to be obeyed if the previous conditional failed.
What is a makefile target?
A simple makefile consists of “rules” with the following shape: target … : prerequisites … recipe … … A target is usually the name of a file that is generated by a program; examples of targets are executable or object files. A target can also be the name of an action to carry out, such as ‘ clean ‘ (see Phony Targets).
What is?= In makefile?
?= indicates to set the KDIR variable only if it’s not set/doesn’t have a value. For example: KDIR?= “foo” KDIR?= “bar” test: echo $(KDIR) Would print “foo” GNU manual: http://www.gnu.org/software/make/manual/html_node/Setting.html.
What is in makefile?
A makefile is a special file, containing shell commands, that you create and name makefile (or Makefile depending upon the system). The makefile contains a list of rules. These rules tell the system what commands you want to be executed. Most times, these rules are commands to compile(or recompile) a series of files.
What are make files?
A makefile is a special file, containing shell commands, that you create and name makefile (or Makefile depending upon the system). While in the directory containing this makefile, you will type make and the commands in the makefile will be executed.
What is Makecmdgoals?
MAKECMDGOALS. The targets given to make on the command line. Setting this variable has no effect on the operation of make. See Arguments to Specify the Goals.
What is a make rule?
A rule appears in the makefile and says when and how to remake certain files, called the rule’s targets (most often only one per rule). It lists the other files that are the prerequisites of the target, and the recipe to use to create or update the target.
What is C make file?
Makefile is a set of commands (similar to terminal commands) with variable names and targets to create object file and to remove them. In a single make file we can create multiple targets to compile and to remove object, binary files. c file contains the user defined function, The third file which is server.
What is 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.
When to use IFEQ or else in makefile?
The lines of the makefile following the ifeq are obeyed if the two arguments match; otherwise they are ignored. The else directive causes the following lines to be obeyed if the previous conditional failed. In the example above, this means that the second alternative linking command is used whenever the first alternative is not used.
When to use a negative comparison in IFEQ?
I.e. if you instead have something like: And then do e.g. make VAR1=4 VAR2=4, the filter will return 4 4, which is not equal to 4. where a negative comparison against an empty string is used instead ( filter will return en empty string if GCC_MINOR doesn’t match the arguments). Using the VAR1 / VAR2 example it would look like this:
Do you have to use POSIX make for IFEQ?
But you have to use a portable, non-anemic make, like GNU make ( gmake ), and not Posix’s make. And it does not address the issue of logical AND and OR.
How to avoid stack overflow in IFEQ branch?
If VAR1 is 4 5, the filter result is 4 5 and the ifneq expression is true. One easy alternative is to just put the same operation in both the ifeq and else ifeq branch, e.g. like this: You can introduce another variable. It doesnt consolidate both checks, but it at least avoids having to put the body in twice: