On Tue, 2022-11-22 at 11:12 +0800, Changqing Li wrote: > Here is what the make manual says, > > 6.10 Variables from the Environment
It's not really related to this section. It's related to how the shell function works. From that section of the manual we see: | All variables that are marked as export will also be passed to the | shell started by the shell function. In your example, KBUILD_OUTPUT is coming from the environment, and all variables imported from the environment automatically exported. So, the value of the KBUILD_OUTPUT variable set in the makefile is exported to the shell function. However, this behavior is new in GNU make 4.4. > the value in shell environment like what 4.3 done. But I don't find > which commit or bug ID is for fixing this issue, so I send this mail > to double check with the exports at this. Thanks a lot. See this from the NEWS file for GNU make 4.4: https://git.savannah.gnu.org/cgit/make.git/tree/NEWS?h=4.4&id=ed493f6c9116cc217b99c2cfa6a95f15803235a2#n74 > * WARNING: Backward-incompatibility! > Previously makefile variables marked as export were not exported to commands > started by the $(shell ...) function. Now, all exported variables are > exported to $(shell ...). This is the reason for the difference in behavior you see.
