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This article focuses on "how to understand linux link compilation", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to understand linux link compilation.

Why include header files instead of .c files

Test the code:

The code is as follows:

M.c file:

# include "t.c"

Int main ()

{

Test ()

Return 0

}

Compile:

The code is as follows:

Gcc m.c-o m-Wall

In file included from m.c:1:0:

T.C: in the function 'test':

T.c:3:2: warning: implicitly declare the function 'putchar' [- Wimplicit-function-declaration]

The compilation passes with only one warning, generates the executable m, runs it normally, and outputs a space.

Modify the following t.c file:

The code is as follows:

# include

Void test ()

{

Printf ("test\ n")

}

Execute after compilation

Output: test

From this, it can be seen that the inclusion of .c files does not have any impact on the program, but is more direct and convenient than including .h files. Here, we mainly take into account the direct connection of various files in large-scale projects, such as A.C file packed M.C file, B.C file contains M.C file, and A.C file contains B.C file, then an error will be reported when compiling, and the function name will be redefined.

The difference between # include and # include "":

For header files contained in angle brackets, gcc first looks for the directory specified by the-I option, and then looks for the system's header file directory (usually / usr/include, including / usr/lib/gcc/i486-linux-gnu/4.3.2/include on my system) For header files contained in quotation marks, gcc first looks for the directory where the .c file contains the header file, then looks for the directory specified by the-I option, and finally looks for the system's header file directory.

Static library

The code is as follows:

/ * stack.c * /

Char stack [512]

Int top =-1

The code is as follows:

/ * push.c * /

Extern char stack [512]

Extern int top

Void push (char c)

{

Stack [+ + top] = c

}

The code is as follows:

/ * pop.c * /

Extern char stack [512]

Extern int top

Char pop (void)

{

Return stack [top--]

}

The code is as follows:

/ * is_empty.c * /

Extern int top

Int is_empty (void)

{

Return top =-1

}

The code is as follows:

/ * stack.h * /

# ifndef STACK_H

# define STACK_H

Extern void push (char)

Extern char pop (void)

Extern int is_empty (void)

# endif

The code is as follows:

/ * main.c * /

# include

# include "stack.h"

Int main (void)

{

Push ('a')

Char c = pop ()

Printf ("% c\ n", c)

Return 0

}

Put the above five .c files and one .h file in the same directory, create a new Makefile file in the current directory, and compile using Makefile.

The code is as follows:

Main:libstack.a main.o

Gcc-o main main.o-L. -lstack

Libstack.a: stack.o push.o pop.o is_empty.o

Ar rs libstack.a stack.o push.o pop.o is_empty.o

Stack.o:

Gcc-o stack.o-c stack.c

Push.o

Gcc-o push.o-c push.c

Pop.o:

Gcc-o pop.o-c pop.c

Is_empty:

Gcc-o is_empty.o-c is_empty.c

Main.o:

Gcc-o main.o-c main.c

Execute. / main after compilation

Display: a

Decompilation directive: view decompiled programs

The code is as follows:

Objdump-d main

At this point, I believe you have a deeper understanding of "how to understand linux link compilation", might as well come to the actual operation of it! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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