请问关于HOSTTYPE与MACHTYPE

faxian

我的系统里是这样的:
HOSTTYPE=i486
MACHTYPE=i486-pc-linux-gnu
我的cpu是p III.
这两个变量是安装系统时默认的?大家的也是这样吗?
这表示debian库的软件默认是对486优化的吗?
如果改成i686会有什么影响?比如编译内核?
我发现相关的程序是gcc和libc6.
下面是dpkg -S i486-pc-linux-gnu的结果:
gcc: /usr/bin/i486-linux-gnu-gcc
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/README
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/crtbeginT.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/libgcc_eh.a
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/crtendS.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/stdarg.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/emmintrin.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/libgcc_s_64.so
gcc-4.0: /usr/bin/i486-linux-gnu-gcc-4.0
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/crtend.o
gcc: /usr/share/man/man1/i486-linux-gnu-gcc.1.gz
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/syslimits.h
cpp-4.0, gcc-4.0: /usr/lib/gcc/i486-linux-gnu
libc6: /lib/ldconfig/i486-linux-gnu-usr-lib
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/libgcc_s.so
cpp-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/cc1
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/mm3dnow.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/pmmintrin.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/crtend.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/iso646.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/crtbeginS.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/limits.h
cpp-4.0: /usr/share/man/man1/i486-linux-gnu-cpp-4.0.1.gz
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/libgcov.a
cpp-4.0: /usr/bin/i486-linux-gnu-cpp-4.0
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/stddef.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/crtendS.o
libc6: /usr/share/doc/libc6/log-test-i486-linux-gnu-libc.gz
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/float.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/mmintrin.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/unwind.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/crtbegin.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/stdbool.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/asm
libc6: /lib/i486-linux-gnu
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/varargs.h
cpp-4.0, gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/crtbeginT.o
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/asm/posix_types.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/libgcc_eh.a
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/crtbeginS.o
cpp: /usr/bin/i486-linux-gnu-cpp
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/libgcov.a
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/64/libgcc.a
libc6: /lib/ldconfig/i486-linux-gnu-lib
gcc-4.0: /usr/share/man/man1/i486-linux-gnu-gcc-4.0.1.gz
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/SYSCALLS.c.X
cpp: /usr/share/man/man1/i486-linux-gnu-cpp.1.gz
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/libgcc.a
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/xmmintrin.h
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/libgcc_s.so
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/collect2
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/crtbegin.o
libc6: /usr/lib/i486-linux-gnu
gcc-4.0: /usr/lib/gcc/i486-linux-gnu/4.0.3/include/mm_malloc.h

faxian

这时bash man中的解释:
HOSTTYPE
              Automatically set to a string that uniquely describes  the  type
              of  machine  on which bash is executing.  The default is system-
              dependent.
MACHTYPE
              Automatically  set  to  a string that fully describes the system
              type on which bash is executing, in the  standard  GNU  cpu-com-
              pany-system format.  The default is system-dependent.
这里说是自动设定的,那么根据什么设的?自己不能改吗?

faxian

另外这两个不是环境变量.