读书时间 2010-05-24 C/C++_读书时间c++-优快云博客

《Linux高级程序设计》2nd version，杨宗德

1. 杂问

Q：我们的系统如何保持其OS可移植性的？使用ANSI库吗？

2. extern

好像只有变量需要extern声明，function不需要，如下例：

[root@frank extern]# cat file.c
#include <stdio.h>
int i=0;
void test() {
printf("in function: i=%d/n", i);
}

[root@frank extern]# cat test.c
#include <stdio.h>
//extern i;
int main() {
//      printf("in main, i=%d/n", i);
        test();
        return 0;
}

T：Got it ! 函数的默认storage type为extern，所以无需显式声明。

3. valgrind，内存调试工具

[root@frank valgrind]# cat sample.c
#include <stdio.h>

int main() {
        int i[5];
        if (i[0] == 0) {
                i[1]=1;
        }
        return 0;
}

[root@frank valgrind]# valgrind --tool=memcheck --leak-check=yes --show-reachable=yes ./sample
==3545== Memcheck, a memory error detector.
==3545== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
==3545== Using LibVEX rev 1658, a library for dynamic binary translation.
==3545== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
==3545== Using valgrind-3.2.1, a dynamic binary instrumentation framework.
==3545== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
==3545== For more details, rerun with: -v
==3545==
==3545== Conditional jump or move depends on uninitialised value(s)
==3545== at 0x804836A: main (in /study/books/alp2/valgrind/sample)
==3545==
==3545== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 13 from 1)
==3545== malloc/free: in use at exit: 0 bytes in 0 blocks.
==3545== malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
==3545== For counts of detected errors, rerun with: -v
==3545== All heap blocks were freed -- no leaks are possible.