What's the differences between -m32, -m64, and nothing in gcc's options?

Question

gcc -m32 main.cpp

gcc -m64 main.cpp

gcc main.cpp

What's the differences between -m32, -m64, and nothing in gcc's options?

Anuradhapura

You can run man gcc to find the answer, or read here. The default flag used is determined by how the compiler was configured when built, usually implying -m64 for 64-bit environments. – Doerr

Answer 1

Refer to gcc Manual Page [here], it indicates

-m32 -m64 Generate code for a 32-bit or 64-bit environment. 

The 32-bit environment sets int, long and pointer to 32 bits and 
generates code that runs on any i386 system. 

The 64-bit environment sets int to 32 bits and long and pointer to 
64 bits and generates code for AMD 's x86-64 architecture. 
For darwin only the -m64 option turns off the -fno-pic and -mdynamic-no-pic options. 

Cristincristina

And I'm assuming that nothing means it just defaults to whatever the local system's architecture is? – Earthstar