Re: x86 Debian 下的 gcc 默认生成的目标文件究竟是 i486 还是 i686 ?

[wolf python london <lyh19901223@gmail.com>]

2012/3/11 Plain_Text <resation@gmail.com>:
>
>
> 　　前几天列表里讨论了相关问题，我做了一个这样的试验。
>
> $ gcc -c main.c -o main.o
> $ gcc -march=i486 -c main.c -o main_i486.o
> $ gcc -march=i686 -c main.c -o main_i686.o
>
> $ diff main.o main_i486.o
> Binary files main.o and main_486.o differ
>
> $ diff main.o main_i686.o
>
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i486-linux-gnu/4.6/lto-wrapper
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian
4.6.3-1' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin
--enable-objc-gc --enable-targets=all --with-arch-32=i586
--with-tune=generic --enable-checking=release --build=i486-linux-gnu
--host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.6.3 (Debian 4.6.3-1)

可能问题是在这里： --with-tune=generic 这个参数指定了缺省值是i686
**quotation**
-mtune=generic can now be used to generate code running well on common
x86 chips. This includes AMD Athlon, AMD Opteron, Intel Pentium-M,
Intel Pentium 4 and Intel Core 2.
(http://gcc.gnu.org/gcc-4.2/changes.html)
**quotation**
>
> 　　其中 main.c 是一个简单的 C 程序。可以看出，默认生成的是 i686 版本。
> 可问题是，在 gcc -v 下却看到 Target: i486-linux-gnu .
>
> 　　究竟是怎么回事？
>
>
>
>
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wolf python london(WPL)
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