review

Author: vonzhou

chapter7/README

@@ -0,0 +1,14 @@
+
+CODE：
+P449  - main.c   swap.c
+P455 - foo3.c   bar3.c 
+P458  - addvec.c multvec.c  main2.c 
+
+
+Blogs:
+1.探寻ELF文件内部：
+http://blog.csdn.net/vonzhoufz/article/details/44925439
+
+2.创建并使用静态库（ar 命令）
+http://blog.csdn.net/vonzhoufz/article/details/44463977
+

chapter7/README~

@@ -0,0 +1,14 @@
+
+CODE：
+P449  - main.c   swap.c
+P455 - foo3.c   bar3.c 
+P458  - addvec.c multvec.c  main2.c 
+
+
+
+1.探寻ELF文件内部：
+http://blog.csdn.net/vonzhoufz/article/details/44925439
+
+2.创建并使用静态库（ar 命令）
+http://blog.csdn.net/vonzhoufz/article/details/44463977
+

chapter7/addvec.c

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+/* addvec.c */
+void addvec(int *x, int *y,
+	    int *z, int n) 
+{
+    int i;
+
+    for (i = 0; i < n; i++)
+	z[i] = x[i] + y[i];
+}
+

chapter7/bar3.c

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+
+int x ;//weak;
+
+int f(){
+	x = 15212;
+}

chapter7/bar4.c

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+
+int x ;//weak;
+
+int f(){
+	x = 15212;
+}

chapter7/bar5.c

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+
+double x ;//weak;
+
+int f(){
+	x = -0.0;
+}

chapter7/dll.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+int x[2] = {1, 2};
+int y[2] = {3, 4};
+int z[2];
+
+int main() 
+{
+    void *handle;
+    void (*addvec)(int *, int *, int *, int);
+    char *error; 
+
+    /* dynamically load the shared library that contains addvec() */
+    handle = dlopen("./libvector.so", RTLD_LAZY);
+    if (!handle) {
+	fprintf(stderr, "%s\n", dlerror());
+	exit(1);
+    }
+
+    /* get a pointer to the addvec() function we just loaded */
+    addvec = dlsym(handle, "addvec");
+    if ((error = dlerror()) != NULL) {
+	fprintf(stderr, "%s\n", error);
+	exit(1);
+    }
+
+    /* Now we can call addvec() it just like any other function */
+    addvec(x, y, z, 2);
+    printf("z = [%d %d]\n", z[0], z[1]);
+
+    /* unload the shared library */
+    if (dlclose(handle) < 0) {
+	fprintf(stderr, "%s\n", dlerror());
+	exit(1);
+    }
+    return 0;
+}
+

chapter7/elfstructs.c

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+typedef struct { 
+    int name;        /* string table offset */ 
+    int value;       /* section offset, or VM address */ 
+    int size;        /* object size in bytes */ 
+    char type:4,     /* data, func, section, or src file name (4 bits) */ 
+	 binding:4;  /* local or global (4 bits) */ 
+    char reserved;   /* unused */  
+    char section;    /* section header index, ABS, UNDEF, */ 
+                     /* or COMMON  */  
+} Elf_Symbol; 
+
+typedef struct { 
+    int offset;     /* offset of the reference to relocate */ 
+    int symbol:24,  /* symbol the reference should point to */ 
+	type:8;     /* relocation type */ 
+} Elf32_Rel; 
+

chapter7/foo3.c

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+#include <stdio.h>
+
+void f();
+
+int x = 15213; // strong
+
+int main(){
+	f();
+	printf("x=%d\n", x);
+	return 0;
+}

chapter7/foo4.c

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+#include <stdio.h>
+
+void f();
+
+int x;
+int main(){
+	x = 15213;
+	f();
+	printf("x=%d\n", x);
+	return 0;
+}