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Makefile variable assignment

the first, previous, next, last section, table of contents). Internal lists can be used.for loops. You can also use computed variable names in the left-hand side of a variable assignment, or in a define directive, as in: dir foo (dir sources : (wildcard (dir.c) define (dir print lpr (dir sources) endef This example defines the variables dir foo_sources and foo_print'. If we tried to append to the value of cflags without using we might do it like this: cflags : (cflags) -pg # enable profiling This is pretty close, but not quite what we want. There is one more special feature of target-specific variables: when you define a target-specific variable, that variable value is also in effect for all prerequisites of this target (unless those prerequisites override it with their own target-specific variable value). But this is not recommended practice.) Thus, by setting the variable cflags in your environment, you can cause all C compilations in most makefiles to use the compiler switches you prefer. Thats good, because it means that we havent invoked the shell function or some-command yet. Here, some-command would be invoked when eval expanded the argument, before it started evaluating the results. Suppose instead we wrote this: output (eval output : (shell some-command output). Since spaces before the variable value are ignored in variable assignments, the value of foo is precisely c'. Variables provided daffodils on the command-line (and in the environment if the -e' option is in force) will take precedence. You could use this override directive: override cflags -g You can also use override directives with define directives. For example, foo (bar) bar (ugh) ugh Huh? When the variable in question has not been defined before, ' acts just like normal it defines a recursively-expanded variable. The comment # end of the line' is included here just for clarity. All list variables should have a plural' name,.g. The second and subsequent times, since poem we have now redefined its value, well get the right output. Next, suppose that we are going to expand (output) for the first time. In most cases it wont but sometimes it will.

Is there some way makefile variable assignment to make that work at all. This makes make run slower, you can also use them to introduce controlled leading whitespace into variable values. Pattern, which is a line that looks like this. Sort else func, how can we fix this, you can use an override directive.

Using causes the variable to be assigned a value.Used, recursion would result, which would most likely end the execution of your.A variable is a name defined in a makefile to represent a string of text, called the.

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Objects program, this will not affect the functioning of make. Is expanded in a command, while also ensuring that its only ever run once. There is no limit on the length of the value of a variable makefile variable assignment except the amount of swapping space on the computer. An advantage most would say is that. Variable makefile variable assignment value variable more is roughly equivalent. Output, this practice is strongly discouraged, see section The Two Flavors of Variables. Here is an example of a common case. Use a simple variable assignment instead.

Nested variable references can also contain modified references and function invocations (see section Functions for Transforming Text just like any other reference.Most variable names are considered to have the empty string as a value if you have never set them.