What does "OS ?= Windows_NT" mean in a makefile?
My OS is Windows XP. My make program is clearmake with GNU compatibility. We have number of makefiles that are used to make our libraries and applications. The first few lines of very first makefile that runs are as follows:
##########################
# src/makefiles/Makefile.mk clearmake -C gnu
##########################
# This supports recursive build of a library or application release for
# all supported targets.
# OS - define the host operating system
# Default to Windows_NT if undefined
#
OS ?= Windows_NT
My question is as follows:
Please explain OS ?= Windows_NT.
Thanks.
##########################
# src/makefiles/Makefile.mk clearmake -C gnu
##########################
# This supports recursive build of a library or application release for
# all supported targets.
# OS - define the host operating system
# Default to Windows_NT if undefined
#
OS ?= Windows_NT
My question is as follows:
Please explain OS ?= Windows_NT.
Thanks.
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SOLUTION
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Adrian Sluijters
erm sorry, I forgot to make that a proposed solution...
ASKER
When does clearmake see what architecture and framework it has to run on? Another words, when does line OS ?= WINDOWS_NT excute? When we type clearmake target, then I believe line in the makefile that contains target and it's dependencies executes first. When does OS ?= WINDOWS_NT execute? What is the order of exection? Thanks.
If this line is before any of the targets, I think it gets executed every time before the target lines get executed.
If you don't define OS=something on the make command line, then the make file sees that OS is undefined, and it sets it to WINDOWS_NT.
If you don't define OS=something on the make command line, then the make file sees that OS is undefined, and it sets it to WINDOWS_NT.