Dependency Side Effects
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If a target is specified with a colon (:) in two dependency lines in different locations, and if commands appear after only one of the lines, NMAKE interprets the dependencies as if adjacent or combined. It does not invoke an inference rule for the dependency that has no commands, but instead assumes that the dependencies belong to one description block and executes the commands specified with the other dependency. For example, this set of rules:
bounce.exe : jump.obj
echo Building bounce.exe...
bounce.exe : up.obj
is evaluated as this:
bounce.exe : jump.obj up.obj
echo Building bounce.exe...
This effect does not occur if a double colon (::) is used. For example, this set of rules:
bounce.exe :: jump.obj
echo Building bounce.exe...
bounce.exe :: up.obj
is evaluated as this:
bounce.exe : jump.obj
echo Building bounce.exe...
bounce.exe : up.obj
# invokes an inference rule