What is $$fromfile(), DEP_CMDS ???

[burkav84]

Hello,I have read a qtopia-opensource-4.2.2 "Build System Reference" and can't understand some things:This is a snippet from "Build System Reference":
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dep()

dep(DEFINES+=CALLER=\$$TARGET)
dep(DEFINES+=CALLER=\$$TARGET,DEFINES)

dep() registers a command to be run by dependent projects. For example, a library can use this to affect the link line of dependent projects. A second argument can be passed that causes the command to run (and the variable to be exported) so that same command can be used for both this project and dependent projects.
There are some caveats to dep():* The .pro file is processed using the qmake function $$fromfile().* Only the DEP_CMDS variable is sent to the calling context.* Processing stops at the .pro file with $$fromfile(), that is, no post-processing occurs.* $$varname can be used to have a variable evaluated in the calling context.
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My questoions are:

1. What is qmake function $$fromfile() - where I can find it's description ? - I searched in qmake reference, but coldn't find it there.

2. What is DEP_CMDS variable ? - I could not understand it from this context.

3. What means "no post-processing occurs" ?

4. What is "$$varname" ? - I could not understand it from this context.

Thanks.