C + + Learning-GCC compilation process View assembly code

• • Gcc
    • GCC parameters
    • Example

Gcc

GCC is very familiar, is a compiler, powerful, full name is: GUN gcc.

In peacetime everyone is simply called: GCC, Powerful, able to compile a lot of languages. Includes: c, C + +, Java, Ada, etc...

GCC parameters

GCC usually has a lot of parameters, in peacetime when I compile small programs, are directly gcc -o object source.c on it.

But one time I wanted to see the same thing. But the two codes that are written differently are different in the execution efficiency. So I checked the parameters of the assembly code in the GCC compilation process.

Parameters	Description
-C	Compile no links only, generate *.o files
-S	Generating assembly code *.s files
-E	Precompiled build *.i File
-G	Debugging information is included in the executable program and can be debugged with GDB.
-O	Export the output file to the specified file
-static	Link Static link library
-library	link Libraries named Library

Example

The use of the method is relatively simple:

• Pre-compile first:

gcc -E hello.c -o hello.i

So we get a precompiled file.
There are some:

# 1 "Main.cpp"# 1 "<built-in>" 1# 1 "<built-in>" 3# 175 "<built-in>" 3# 1 "<command line>" 1# 1 "<built-in>" 2# 1 "Main.cpp" 2# 1 "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/iostream " 1 3# Panax Notoginseng "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/iostream " 3# 1 "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/__config " 1 3#  - "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/__config " 3# 226 "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/__config " 3typedef __char16_t CHAR16_T;TYPEDEF __char32_t char32_t;# 349 "/applications/xcode.app/contents/developer/toolchains/xcodedefault.xctoolchain/usr/bin/. /include/c++/v1/__config " 3...

As such, it is to put some of the head files inside God horse.

• You can then link:

gcc -S hello.i -o hello.s

Inside is the assembler code. As follows:

    . section__text,__text,regular,pure_instructions. section__text,__const. Align  4Lcpi0_0:    . Long   1127219200              # # 0x43300000    . Long   1160773632              # # 0x45300000    . Long   0                       # # 0x0    . Long   0                       # # 0x0lcpi0_1:    . Quad   4841369599423283200     # # Double 4.503600e+15    . Quad   4985484787499139072     # # Double 1.934281e+25    . section__text,__text,regular,pure_instructions. Globl_main. Align  4,0x90_main:                                  # # @main    . CFI_startproc# # Bb#0:Pushq%RBPLTMP2:    . CFI_def_cfa_offset -Ltmp3:    . CFI_offset%RBP,- -Movq%rsp,%RBP ...

Forgive me for the assembly compared to idiot, I can only read a little bit of assembly code, want to learn all dragged a long time TT

• It is then compiled, and does not link to the birth .o file.

gcc -c hello.s -o hello.o

This time there is no way to open the view with a text editor. It is already a binary file. It's all open 0 1 , too.
I opened it with sublime Text 2 and it was a bunch of 16-binary code.

• Then generate the executable file:

gcc hello.o -o hello

At this point, the link is successful and compiled into an executable file.

Just use ./hello it when you're done.

C + + Learning-GCC compilation process View assembly code