GCC compiling dynamic and static libraries

gcc Common options and dynamic library static library

One 、gcc summary

• compiler (Compiler) hold Source code is converted to other lower level code ( For example, binary code 、 Machine code ), But it won't be executed .
• Interpreter (Interpreter) Will read the source code , And generate instructions directly Let the computer hardware execute , No other code will be output .
• gcc It started as C Linguistic compiler , But later the function was expanded , Become able to support compiling more languages , for example C++、Java、Go、Objective -C etc. , So later gcc It was renamed GNU Compiler Suite （GNU Compiler Collection Compiler collection ）.
• gcc The compilation process is based on File suffix To call different compilers
• .c There are four steps to generate an executable file from a file precompile 、 assembly 、 compile 、 link

Two 、gcc Common options

test.c

#include <stdio.h>

int main(int argc, char *argv[])
{
     
 	printf("Hello world!\n");

    return 0;
}

1. -E ： precompile gcc -E test.c

   Execute to precompile , Replace the code text . Output precompiled results to standard output （ It's usually a monitor ）

2. -S ： assembly gcc -S test.c

   Execution to assembly , Source code to assembly code conversion , Output assembly code （.s file ）

3. -c ： compile gcc -c test.c

   Execute to compile , Output target file （.o file ）

4. -o ： change gcc Output file name

If you want to use it gcc Generate executable files , Can directly gcc test.o Generate executable files a.out,gcc test.o -o test You can rename the generated executable a.out Designated for us test（ from .o The process from file to executable file is actually the process of linking ）

5. -shared And -fPIC： Create a dynamic library
   -fPIC：（Position-Independent Code） It works on Compile phase , Tell the compiler to generate Location independent code （.o file ）

   -shared： Will be multiple .o The file is linked into a .so Dynamic library files

​ Will now print ”Hello world!“ The function of is encapsulated into a function , And will hello.c Make dynamic library and static library respectively , stay test.c Of main() In the static library or dynamic library hello() To print “Hello world!”

hello.h

#ifndef _HELLO_H_ // A defensive statement 
#define _HELLO_H_

extern int hello();

#endif

hello.c

#include <stdio.h>

int hello()
{
     
	printf("Hello world!\n");

	return 0;
}

test.c

#include <stdio.h>
#include "hello.h"

int main(int argc, char *argv[])
{
     
	hello();

return 0;
}

6. -I( uppercase i)： towards gcc Add header file search path to
   
7. -l( Lowercase L)： Specify the library to link
8. -L： towards gcc China Canada stock in path

Dynamic links require... At run time export Introduce the dynamic library path to the lookup path to link , Static links don't need

9. -static： Link static libraries

10. -w： Turn off the warning
11. -Wall： Turn on all warnings
12. -g： Generate object code with debug information