Linux link compilation detailed _linux shell

Why should I include a header file instead of a. c file

Test code:

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M.C file:
#include "t.c"
int main ()
{
Test ();
return 0;
}

Compile:

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GCC M.c-o m-wall

In the file included from m.c:1:0:
T.C: In the function ' test ':
T.c:3:2: Warning: Implicit declaration of function ' Putchar ' [-wimplicit-function-declaration]
Compile through, with only one warning, generate executable m, run it normally, output a space.

Modify the following t.c file:

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#include <stdio.h>
void Test ()
{
printf ("test\n");
}

Post-Compile execution

Output: Test

From this, it can be seen that the inclusion of the. c file does not affect the program, but more directly than the inclusion of the. h file, which mainly takes into account large projects, the direct links between the documents, such as A.C file M.c file, B.C The file contains the M.c file, and the A.C file contains the B.C file, the error occurs at compile time, and the function name is redefined.
The difference between #include <> and #include "":

For header files that are included with angle brackets, GCC first finds the directory specified by the-I option, and then looks for the system header directory (usually/usr/include, which also includes/usr/lib/gcc/i486-linux-gnu/4.3.2/include on my system) Instead, for the header file enclosed in quotation marks, GCC first finds the directory containing the. c file that contains the header file, finds the directory specified by the-I option, and then finds the system's header file directory.


Static Library

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* STACK.C * *
Char stack[512];
int top =-1;

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* PUSH.C * *
extern Char stack[512];
extern int top;
void push (char c)
{
Stack[++top] = c;
}

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* POP.C * *
extern Char stack[512];
extern int top;
Char pop (void)
{
return stack[top--];
}

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* IS_EMPTY.C * *
extern int top;
int is_empty (void)
{
return top = = 1;
}

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* Stack.h * *
#ifndef Stack_h
#define Stack_h
extern void push (char);
extern char pop (void);
extern int is_empty (void);
#endif

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* MAIN.C * *
#include <stdio.h>
#include "Stack.h"
int main (void)
{
Push (' a ');
char c = pop ();
printf ("%c\n", c);
return 0;
}

In the same directory as the 5. c files and one. h file, create a new makefile file in the current directory, and use makefile to compile.

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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

Executed after compilation./main
Show: A

Anti-compile directive: View anti-compile program

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objdump-d Main