C/C ++ learning and learning

C/C ++ learning and learning

• • GCC
    • GCC Parameters
    • Example

GCC

Everyone is familiar with gcc. It is a compiler with powerful functions. Its full name is: gun gcc.

Generally, it is called GCC, which has powerful functions and can compile many languages. Including c, c ++, java, ada, etc...

GCC Parameters

Gcc usually has many parameters. When I compile a small programgcc -o object source.cYou can.

But one time I wanted to check whether there were differences in execution efficiency between the two codes with the same purpose but different writing methods. So I checked the assembly code parameters during gcc compilation.

Parameters	Description
-C	Only compile without link, generate*.oFile
-S	Generate assembly code*.sFile
-E	Pre-compile generation*.iFile
-G	Debugging information is included in the executable program, which can be debugged by gdb.
-O	Output the output file to the specified file.
-Static	Link Static Link Library
-Library	Link library

Example

Easy to use:

• First, pre-compile:

gcc -E hello.c -o hello.i

In this way, we get a pre-compiled 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# 37 "/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# 16 "/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...

Something like this is to put some header files in it.

• Then you can link:

gcc -S hello.i -o hello.s

It is the assembly 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 16Ltmp3:    .cfi_offset %rbp, -16    movq    %rsp, %rbp...

Forgive me for being an idiot in assembly. I can only understand a little bit of assembly code, but it has been a long time for me to learn TT.

• Then compile and generate without Link.oFile.

gcc -c hello.s -o hello.o

At this time, you cannot open it in a text editor. It is already a binary file. Both open and open0 1Now
After I opened it with sublime text 2, there were a bunch of hexadecimal code.

• Then generate the executable file:

gcc hello.o -o hello

At this time, the link is successfully compiled into an executable file.

Only used for execution./helloYou can.