Running specific part of a Makefile under a specific shell

[thutt]

peter0x44 writes:
 > Hi all,
 > I have a Makefile that is intended for running under both Windows and 
 > Linux, for the raylib library.
 > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fraysan5%2Fraylib%2Fblob%2Fmaster%2Fsrc%2FMakefile&data=04%7C01%7Cthutt%40vmware.com%7C94bfbd5076e74e217f3808d9ecf84394%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C1%7C637801373333085947%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=PGZlG3XNgbWY%2BPZt9ebcCAJU848kQOHAU7ggfiNV8G4%3D&reserved=0
 > 
 > This Makefile, under Windows, for the `make clean` target uses the del 
 > builtin command of cmd.exe to delete files.
 > 
 > clean:
 > ifeq ($(PLATFORM_OS),WINDOWS)
 >          del *.o /s
 >          cd $(RAYLIB_RELEASE_PATH)
 >          del lib$(RAYLIB_LIB_NAME).a /s
 >          del lib$(RAYLIB_LIB_NAME)dll.a /s
 >          del $(RAYLIB_LIB_NAME).dll /s
 > else
 > 
 > However, that the shell is always cmd.exe is a bad assumption on 
 > Windows, as this won't be true if GNU Make finds sh.exe in the PATH, so 
 > this target will fail in those circumstances.
 > I am aware I can change the shell used to run build rules with the 
 > variable SHELL, `make clean SHELL=cmd` always works.
 > But I would rather not have to enforce this under those situations, and 
 > allow the same command to work by default regardless of whether the 
 > shell is sh.exe or cmd.exe.
 > 
 > Is there a way I can change the shell *right before* running the del 
 > command? inserting SHELL = cmd before it will result in it being 
 > interpreted as a shell command, that obviously fails.
 > I'm not experienced enough with Makefiles to know the proper syntax to 
 > do this, or if it is even possible, so that is why I am asking here.

Try the following:

$(if $(filter $(HOSTOS),linux windows),,$(error HostOS not set to (linux | 
windows)))

clean:  clean_$(HOSTOS)
        @echo "Cleaned";

clean_windows:  SHELL:=cmd.exe

clean_windows:
        @echo "$@: SHELL is set to '$(SHELL)'"


clean_linux:
        @echo "$@: SHELL is set to '$(SHELL)'"


It's a good general pattern for removing conditionalization in
Makefiles -- making them easier to read, IMHO.


 > 
 > The reason I only wish to do this for the `make clean` target, and not 
 > run the entire Makefile under cmd.exe is because this same Makefile is 
 > also used to cross-compile the library from another OS, so this will 
 > cause the entire Makefile to fail on those operating systems.
 > 
 > Thanks for your time,
 > Peter D.
 > 

-- 
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