"Pthread.h" not found problem encountered in compiling GCC

stay LFS Of The fifth chapter Compile from source freestanding Of GCC The following error is reported

./gthr-default.h:35:10: fatal error: pthread.h: No such file or directory
   35 | #include <pthread.h>

The reference configuration instructions given in the book are

../configure                  \
    --target=$LFS_TGT         \
    --prefix=$LFS/tools       \
    --with-glibc-version=2.35 \
    --with-sysroot=$LFS       \
    --with-newlib             \
    --without-headers         \
    --enable-initfini-array   \
    --disable-nls             \
    --disable-shared          \
    --disable-multilib        \
    --disable-decimal-float   \
    --disable-threads         \
    --disable-libatomic       \
    --disable-libgomp         \
    --disable-libquadmath     \
    --disable-libssp          \
    --disable-libvtv          \
    --disable-libstdcxx       \
    --enable-languages=c,c++

I first tried to delete the above pile disable, The following configuration instructions are used （ Mainly curiosity configure Will it automatically infer some libraries and feature There is no way to support , such as threads）

../configure                  \
    --target=$LFS_TGT         \
    --prefix=$LFS/tools       \
    --with-glibc-version=2.35 \
    --with-sysroot=$LFS       \
    --with-newlib             \
    --without-headers         \
    --enable-initfini-array   \
    --disable-nls             \
    --disable-shared          \
    --disable-multilib        \

And then, sure enough , I got the following error report

./gthr-default.h:35:10: fatal error: pthread.h: No such file or directory
   35 | #include <pthread.h>

So I tried make clean, Then use the configuration instructions in the book to re configure. What's puzzling is , Still got the above pthread.h not found The error of （ Expected due to the removal of thread support , Should no longer rely on pthread.h The header file ）.

Discover the use of rm -rf * hold build Delete all directories and then re configure It was successful . This description is the previous make clean Didn't say that the configuration file was deleted completely .

After a search , Found out GNU automake Description of and GNU coding styles Explanation .

on top coding styles The following instructions are included in the documentation for

‘clean’
Delete all files in the current directory that are normally created by building the program. Also delete files in other directories if they are created by this makefile. However, don’t delete the files that record the configuration. Also preserve files that could be made by building, but normally aren’t because the distribution comes with them. There is no need to delete parent directories that were created with ‘mkdir -p’, since they could have existed anyway.

‘distclean’
Delete all files in the current directory (or created by this makefile) that are created by configuring or building the program. If you have unpacked the source and built the program without creating any other files, ‘make distclean’ should leave only the files that were in the distribution. However, there is no need to delete parent directories that were created with ‘mkdir -p’, since they could have existed anyway.
Delete .dvi files here if they are not part of the distribution.

on top automake In the document , The following are defined clean semantics

• If make built it, and it is commonly something that one would want to rebuild (for instance, a .o file), then mostlyclean should delete it.
• Otherwise, if make built it, then clean should delete it.
• If configure built it, then distclean should delete it.
• If the maintainer built it (for instance, a .info file), then maintainer-clean should delete it. However maintainer-clean should not delete anything that needs to exist in order to run ‘./configure && make’.

So the problem with my previous operation is that I shouldn't use make clean, Instead, use make distclean.