[GitHub] [incubator-nuttx-apps] anchao edited a comment on pull request #395: make/clean: clean the OBJ directly if declare in subdirectory

[GitBox <gi...@apache.org>]

anchao edited a comment on pull request #395:
URL: https://github.com/apache/incubator-nuttx-apps/pull/395#issuecomment-694942015


   Hi @v01d,
   
   Yes, thanks for review, totally agree with you!
   
   Let me first introduce the cause of this issue first,
   In some open source projects, we often encounter files with the same source file name but in different directories, 
   for example:
   
   ```
   chao@archer:~/code/apps/examples/hello$ tree
   .
   ├── hello_main.c
   ├── Kconfig
   ├── Make.defs
   ├── Makefile
   ├── test
   │   └── test.c
   └── test2
       └── test.c
   ```
   
   
   If we use VPATH to build this project, we will find that only one file is compiled because VPATH mistakenly believes that another file is already dependent:
   
   Makefile:
   
   ```
   include $(APPDIR)/Make.defs
   ...
   VPATH := test test2
   CSRCS += test.c test.c
   ....
   include $(APPDIR)/Application.mk
   ```
   
   Compile object:
   
   ```
   chao@archer:~/code/apps/examples/hello$ tree
   .
   ├── hello_main.c
   ├── hello_main.home.chao.code.apps.examples.hello.o
   ├── Kconfig
   ├── Make.defs
   ├── Make.dep
   ├── Makefile
   ├── test
   │   └── test.c
   ├── test2
   │   └── test.c
   └── test.home.chao.code.apps.examples.hello.o
   ```
   
   So VPATH is not a good choice in this case, we must use relative paths to ensure that the files are compiled:
   
   Makefile:
   ```
   include $(APPDIR)/Make.defs
   ...
   CSRCS += test/test.c test2/test.c
   ...
   include $(APPDIR)/Application.mk
   ```
   
   compile object:
   
   ```
   chao@archer:~/code/apps/examples/hello$ tree
   .
   ├── hello_main.c
   ├── hello_main.home.chao.code.apps.examples.hello.o
   ├── Kconfig
   ├── Make.defs
   ├── Make.dep
   ├── Makefile
   ├── test
   │   ├── test.c
   │   └── test.home.chao.code.apps.examples.hello.o
   └── test2
       ├── test.c
       └── test.home.chao.code.apps.examples.hello.o
   ```
   
   As you see, the source code was compiled correctly, then we encountered a new problem, "How to clear it?"
   
   I have traversed a lot of source code in nuttx , the build system of nuttx is basically built with VPATH, so there is no case where the source code file names are the same.
   
   Therefore, this clean process will be a special and partially effective process. In order to reduce the damage, I only take effect when building external applications, I think this is a comprehensive consideration for a lot of 3rd open source project.


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