诺 之 林

发表于 更新于 分类于

首先看如下一段代码:

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#include <stdio.h>

void static_usage()
{
        static int s = 0;

        if(s == 0)
        {
                s = 1;
                printf("s equals 0\n");
        }
        else
        {
                printf("s equals 1\n");
        }
}

int main(void)
{
        int i = 0;

        for(i = 0; i < 5; ++i)
        {
                static_usage();
        }

        return 0;
}

实际打印结果:

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s equals 0
s equals 1
s equals 1
s equals 1
s equals 1
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s equals 0
s equals 0
s equals 0
s equals 0
s equals 0
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发表于 更新于 分类于

1：/dev/null就是一个黑洞，不想要的东西重定向它即可

举例：find ./ -name “xyz” 2> /dev/null

解释：这样标准错误信息将被放入黑洞消失

2：/dev/zero有类似memset的功能，填充0×00(不是指ACII的’0′)

举例：dd if=/dev/zero of=xyz bs=1M count=10

解释：新建一个10M大小的空文件(填充的是0×00，可用hexdump命令查看)

发表于 更新于 分类于

背景：

安装ubuntu0804，第一个分区是swap分区(/dev/sda1)，第二个分区是”boot”分区(dev/sda2)，第三个分区是跟目录”/”分区(/dev/sda3)

如果”boot”分区和”/”分区在同一个分区，请根据自身实际情况进行修改

1:grub的三个主要引导文件

(1)/boot/grub/stage1与mbr一样也是512bytes大小，前446bytes也与mbr相同，

    即stage1文件是bootloader本地备份，但stage1文件446bytes之后64bytes的partition tables是无效的
    
    因为grub在安装mbr的时候会根据实际分区情况来填写mbr中的partition tables
    
    stage1文件的最后两个bytes与mbr一样也是”0x55aa”
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发表于 更新于 分类于

我们从最简单的”hello world”开始，新建hello.c文件代码如下:

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#include <stdio.h>

int main(void)
{
    printf("Hello World\n");
    return 0;
}

生产可执行文件的命令如下:

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gcc hello.c -o hello

怎么样，很简单吧，但是到底做了些什么呢?分解动作如下:

第一步：预编译: .c文件 — 预处理后的.i文件

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gcc -E hello.c -o hello.i

那么预编译做了哪些工作呢?

答：

a:将#define删除并展开所有宏

b:处理预编译指令#if #ifdef #else #endif以及#include

c:删除注释

d:添加调试标示(这部分占.i大部分内容)

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发表于 更新于 分类于 
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#! /usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import division 
from Tkinter import * 
from tkFont import Font

def btnClick(ev = None): 
    foodl = '' 
    try: 
        foodl = eval(en.get()) 
    except: 
        pass 
    if isinstance(foodl, (int, float, long)): 
        pass 
    else: 
        foodl = 'Error..' 
    lbl.config(text = foodl) 

#主窗口 
mainView = Tk() 
mainView.title('YuanLin')

ft = Font(family = ('Verdana'), size = 18)
en = Entry(mainView, font = ft) 
btn = Button(mainView, text = '计算(注意运算顺序)', command = btnClick, font = ft) 
lbl = Label(text = '运算符: + - * / % **', font = ft) 

enterEvent = lambda x: x.keycode == 13 and btnClick() 
clickEvent = lambda x: lbl.config(text = '运算符: + - * / % **') 

en.focus() 
en.bind('<Key>', enterEvent) 
en.bind('<Button-1>', clickEvent)

en.pack() 
btn.pack() 
lbl.pack()

mainView.mainloop()

发表于 更新于 分类于 
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#include <stdio.h>
#include <stdbool.h>

// bracket define & function
enum bracket_type
{
	BRACKET_NONE,
	BRACKET_LEFT,
	BRACKET_RIGHT
};

enum bracket_type type(char * c)
{
	enum bracket_type type = BRACKET_NONE;

	if(*c == '(' || *c == '[')
	{
		type = BRACKET_LEFT;
	}	
	else if(*c == ')' || *c == ']')
	{
		type = BRACKET_RIGHT;
	}

	return type;
}

bool match(char * c1, char * c2)
{
	bool ret = false;

	if(*c1 == '(' && *c2 == ')'
		|| *c1 == ')' && *c2 == '('
		|| *c1 == '[' && *c2 == ']'
		|| *c1 == ']' && *c2 == '[')
	{
		ret = true;
	}

	return ret;
}

// stack define & function
#define STACK_SIZE 100

struct my_stack
{
	char data[STACK_SIZE];
	int top;
};

void init(struct my_stack * stack)
{
	stack->top = -1;
}

bool push(struct my_stack * stack, char * c)
{
	bool ret = false;

	if(stack->top < STACK_SIZE)
	{
		stack->data[++stack->top] = *c;

		ret = true;
	}
	else
	{
		ret = false;
	}

	return ret;
}

bool pop(struct my_stack * stack, char * c)
{
	bool ret = false;

	if(stack->top >= 0)
	{
		*c = stack->data[stack->top--];

		ret = true;
	}
	else
	{
		ret = false;
	}

	return ret;
}

int size(struct my_stack * stack)
{
	return stack->top + 1;
}

//brackets_match
bool brackets_match(char *str)
{
	char c;
	char * s = str;
	bool ret = true;

	struct my_stack stack;

	init(&stack);

	while(*s != '\0')
	{
		if(BRACKET_LEFT == type(s))
		{
			push(&stack, s);
		}
		else if(BRACKET_RIGHT == type(s))
		{
			if(pop(&stack, &c) == true)	
			{
				if(match(&c, s) != true)
				{
					ret = false;
					break;
				}
			}
			else
			{
				ret = false;
				break;		
			}
		}

		++s;
	}	

	if(size(&stack) != 0)
	{
		ret = false;
	}

	return ret;
}

int main(void)
{
	int i = 0;
	char * str[3] = {
		"([()([])])",     // match 
		"([()([(])])",    // unmatch
		"([()([])]))"     // unmatch
		}; 

	for(i = 0; i < 3; ++i)
    	{
        	printf("%s\n", brackets_match(str[i]) == true ? "match" : "unmatch");
    	}

	return 0;
}

发表于 更新于 分类于

问题描述

ARM编译环境的头文件time.h中，有如下的时间转换接口:

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extern time_t mktime(struct tm * /*timeptr*/);

如果，传入的实参tm不合法的话，mktime会返回-1

但是，实际的代码却没有返回fasle

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if(-1 == mktime(&result))
{
    return FALSE; // not return false
}

问题分析

原来，此时time_t的类型定义是 typedef unsigned int time_t;(不同编译环境定义各不相同)

所以，导致获取到的实际返回值是一个极大的正值

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(signed int)-1 -> 补码 0xFFFFFFFF -> (unsigned int)4294967295
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发表于 更新于 分类于 
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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

// type define
struct node
{
	void * data;
	struct node * next;  	
};

struct slist
{
	int size;
	struct node * head;
};

typedef void (* slist_print_cb) (void * data);

// declaration
struct slist * slist_create(void);
bool slist_insert(struct slist * list, void * data, int pos);
bool slist_remove(struct slist * list, int pos);
int slist_size(struct slist * list);
void * slist_data(struct slist * list, int pos);
struct node * slist_find(struct slist * list, int pos);

static void slist_print_int(void * data);

// implement
struct slist * slist_create(void)
{
	struct slist * list = NULL;

	list = (struct slist *) malloc(sizeof(struct slist));
	memset(list, 0, sizeof(struct slist));

	list->size = 0;
	list->head = NULL;

	return list;
} 

bool slist_insert(struct slist * list, void * data, int pos)
{
	struct node * prev = NULL;
	struct node * insert = NULL;

	insert = (struct node *) malloc(sizeof(struct node));
	memset(insert, 0, sizeof(struct node));

	insert->data = data;
	insert->next = NULL;

	prev = slist_find(list, pos - 1);
	if(prev)
	{
		insert->next = prev->next;
		prev->next = insert;
	}
	else
	{
		list->head = insert;
	}

	++list->size;

	return true;
}

bool slist_remove(struct slist * list, int pos)
{
	struct node * prev = NULL;
	struct node * remove = NULL;

	prev = slist_find(list, pos - 1);
	remove = slist_find(list, pos);

	if(prev && remove)
	{		
		if(remove == list->head)
		{
			list->head = remove->next;
		}
		else
		{
			prev->next = remove->next;
		}

		free(remove);

		--list->size;
	}

	return true;
}

int slist_size(struct slist * list)
{
	return list->size;
}

void * slist_data(struct slist * list, int pos)
{
	struct node * found = NULL;

	found = slist_find(list, pos);

	if(found)
	{
		return found->data;
	}
	else
	{
		return NULL;
	}
}

struct node * slist_find(struct slist * list, int pos)
{
	int i = 0;
	struct node * found = NULL;

	found = list->head;

	for(i = pos; i > 0; --i)
	{
		if(found)
		{
			found = found->next;
		}
		else
		{
			break;
		}
	}

	return found;
}

void slist_print(void * data, slist_print_cb cb)
{
	if(cb)
	{
		cb(data);
	}
}

static void slist_print_int(void * data)
{
	printf("%d\n", (int) data);
}

int main(void)
{
	struct slist * list = NULL;

	list = slist_create();

	slist_insert(list, (void *)1, 0);
	slist_insert(list, (void *)2, 0);

	slist_print(slist_data(list, 0), slist_print_int); // 1
	slist_print(slist_data(list, 1), slist_print_int); // 2

	slist_remove(list, 0);

	slist_print(slist_data(list, 0), slist_print_int); // 2

	return 0;	
}

发表于 更新于 分类于 
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" All system-wide defaults are set in $VIMRUNTIME/debian.vim (usually just
" /usr/share/vim/vimcurrent/debian.vim) and sourced by the call to :runtime
" you can find below.  If you wish to change any of those settings, you should
" do it in this file (/etc/vim/vimrc), since debian.vim will be overwritten
" everytime an upgrade of the vim packages is performed.  It is recommended to
" make changes after sourcing debian.vim since it alters the value of the
" 'compatible' option.

" This line should not be removed as it ensures that various options are
" properly set to work with the Vim-related packages available in Debian.
runtime! debian.vim

" Uncomment the next line to make Vim more Vi-compatible
" NOTE: debian.vim sets 'nocompatible'.  Setting 'compatible' changes numerous
" options, so any other options should be set AFTER setting 'compatible'.
"set compatible

" Vim5 and later versions support syntax highlighting. Uncommenting the next
" line enables syntax highlighting by default.
syntax on

" If using a dark background within the editing area and syntax highlighting
" turn on this option as well
"set background=dark

" Uncomment the following to have Vim jump to the last position when
" reopening a file
"if has("autocmd")
"  au BufReadPost * if line("'\"") > 0 && line("'\"") <= line("$")
"    \| exe "normal g'\"" | endif
"endif

" Uncomment the following to have Vim load indentation rules according to the
" detected filetype. Per default Debian Vim only load filetype specific
" plugins.
"if has("autocmd")
"  filetype indent on
"endif

" The following are commented out as they cause vim to behave a lot
" differently from regular Vi. They are highly recommended though.
"set showcmd		" Show (partial) command in status line.
"set showmatch		" Show matching brackets.
"set ignorecase		" Do case insensitive matching
"set smartcase		" Do smart case matching
"set incsearch		" Incremental search
"set autowrite		" Automatically save before commands like :next and :make
"set hidden             " Hide buffers when they are abandoned
"set mouse=a		" Enable mouse usage (all modes) in terminals

" Source a global configuration file if available
" XXX Deprecated, please move your changes here in /etc/vim/vimrc
if filereadable("/etc/vim/vimrc.local")
  source /etc/vim/vimrc.local
endif

" added by yuanlin begin
set nu
set autoindent
set cindent
set noswapfile
set autochdir

""""""""""""""""""""""""""""""
" enable backspace key
""""""""""""""""""""""""""""""
set nocompatible 
set backspace=indent,eol,start

""""""""""""""""""""""""""""""
" Tag list (ctags)
""""""""""""""""""""""""""""""
let Tlist_Ctags_Cmd = '/usr/bin/ctags'

let Tlist_Show_One_File = 1
let Tlist_Exit_OnlyWindow = 1
let Tlist_Use_Right_Window = 1   
let Tlist_Auto_Open = 1

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" cscope setting
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
if has("cscope")
	set csprg=/usr/bin/cscope
	set csto=1
	set cst
	set nocsverb
	" add any database in current directory
	"if filereadable("cscope.out")
	"	cs add cscope.out
	"endif
	set csverb
endif

nmap <C-g> :cs find g <C-R>=expand("<cword>")<CR><CR>
nmap <C-f> :cs find f <C-R>=expand("<cfile>")<CR><CR>
nmap <C-c> :cs find c <C-R>=expand("<cword>")<CR><CR>
nmap <C-d> :cs find d <C-R>=expand("<cword>")<CR><CR>
nmap <C-\>t :cs find t <C-R>=expand("<cword>")<CR><CR>
nmap <C-\>s :cs find s <C-R>=expand("<cword>")<CR><CR>
nmap <C-\>e :cs find e <C-R>=expand("<cword>")<CR><CR>
nmap <C-\>i :cs find i <C-R>=expand("<cfile>")<CR>$<CR>

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" add for coding
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
let &termencoding=&encoding
set fileencodings=utf-8,gbk

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" shortcuts
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
nmap <C-z> u
nmap <C-y> <C-r>
nmap <C-n> : tabn <CR>
nmap <C-p> : tabp <CR>
nmap <C-e> : tabe 
nmap <C-o> : TlistToggle <CR>
nmap <C-h> : set hls <CR>
nmap <S-h> : set nohls <CR>

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" NerdCommenter
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
"\cc comment
"\cu uncomment
"\c<space> comment/uncomment
"\ca switch sytle

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" colors
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
color desert

"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
" copy paste
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
set paste

" added by yuanlin end
0%