gcc编译-m32、-mx32有什么区别

先来看看gcc官方手册吧

These ‘-m’ switches are supported in addition to the above on x86-64 processors in 64-bit
environments.
-m32
-m64
-mx32
-m16

-miamcu Generate code for a 16-bit, 32-bit or 64-bit environment.

The ‘-m32’ option
sets int, long, and pointer types to 32 bits, and generates code that runs on
any i386 system.

The ‘-m64’ option sets int to 32 bits and long and pointer types to 64 bits, and
generates code for the x86-64 architecture. For Darwin only the ‘-m64’ option
also turns off the ‘-fno-pic’ and ‘-mdynamic-no-pic’ options.

The ‘-mx32’ option sets int, long, and pointer types to 32 bits, and generates
code for the x86-64 architecture.

The ‘-m16’ option is the same as ‘-m32’, except for that it outputs the
.code16gcc assembly directive at the beginning of the assembly output so
that the binary can run in 16-bit mode.

The ‘-miamcu’ option generates code which conforms to Intel MCU psABI. It
requires the ‘-m32’ option to be turned on.

执行编译的程序需要安装32位lib：

$sudo apt-get install lib32ncurses5 lib32z1

编译时需安装multilib：

sudo apt-get install gcc-multilib g++-multilib

在我的电脑上-m32能够运行，-mx32需要内核支持，在编译内核时有mx32的选项，CentOS7内核和GCC都没开启支持mx32，Debian9内核没开启，但gcc支持

下面是elf读取出来的信息：

-mx32：在64位系统中，指针和long都是64位的（此处只讨论linux，Windows不是），因此程序可以使用的内存大小可以远远大于4GiB。但是很多程序并不需要4GiB以上内存，这样内存地址只使用了低4字节造成一定的浪费，而且对于x86的CPU（准确的说是amd64或x86-64，不含IA64），64位数据运算速度远远慢于32位数据，指针和long是32位既浪费了高4字节的空间，又拖累了运行速度，于是有人搞出了指针和long是32位的mx32：你同样可以使用INT64这样的8字节数据，但编译出的程序体积更小，运行速度更快。