之前似乎是在哪儿有听说过，今天听人正式的说了一下，自己测试了测试，果然如此。
代码如下
编译之后，运行结果是4，char明显变成了一个int
使用DDD跟踪，发现编译器在生成阶段就已经算好sizeof 'A'的值是4，硬编码进去了……
相反，如果之前定义char x = 'a'; 最后输出sizeof x，那这时又变成了1。
发生提升的时候一般都是在表达式中，低于int的整形提升到int，低于double的浮点提升到double。 这个东西完全取决于编译器，上面第二个例子也是编译器提前算好的，只不过由于明确定义了这个东西的类型，所以编译器算出来的是1。 实际上char+char的时候是先int+int然后裁剪成一个char，看看编译出来的代码即知。
全黑看长了总是比较瞎眼睛，做了个简易DLL，果然很瞎
eax返回值不假,但是eax 不就4个字节吗，各种代码通过eax返回时到底有多少花样? have a try:
1、 long long
Dump of assembler code for function fun():
=> 0x00401500 <+0>: push %ebp
0x00401501 <+1>: mov %esp,%ebp
0x00401503 <+3>: mov $0x11223344,%eax
0x00401508 <+8>: mov $0x0,%edx
0x0040150d <+13>: pop %ebp
0x0040150e <+14>: ret
End of assembler dump.
Dump of assembler code for function main(int, char**):
0x0040150f <+0>: push %ebp
0x00401510 <+1>: mov %esp,%ebp
0x00401512 <+3>: and $0xfffffff0,%esp
0x00401515 <+6>: sub $0x10,%esp
0x00401518 <+9>: call 0x409650 <__main>
0x0040151d <+14>: call 0x401500 <fun()>
0x00401522 <+19>: mov %eax,0x8(%esp)
0x00401526 <+23>: mov %edx,0xc(%esp)
0x0040152a <+27>: mov $0x0,%eax
0x0040152f <+32>: leave
0x00401530 <+33>: ret
End of assembler dump.
edx小伙加入了。
2、 真 long long。
事实上又拉了一个战友过来
->->post-prompt
Dump of assembler code for function main(int, char**):
0x0040150f <+0>: push %ebp
0x00401510 <+1>: mov %esp,%ebp
0x00401512 <+3>: and $0xfffffff0,%esp
0x00401515 <+6>: sub $0x10,%esp
0x00401518 <+9>: call 0x409650 <__main>
=> 0x0040151d <+14>: call 0x401500 <fun()>
0x00401522 <+19>: mov %eax,0x8(%esp)
0x00401526 <+23>: mov %edx,0xc(%esp) <==注意这里
0x0040152a <+27>: mov $0x0,%eax
0x0040152f <+32>: leave
0x00401530 <+33>: ret
End of assembler dump.
->->pre-prompt
(gdb)
->->prompt
->->post-prompt
Dump of assembler code for function fun():
0x00401500 <+0>: push %ebp
0x00401501 <+1>: mov %esp,%ebp
0x00401503 <+3>: mov $0x11223344,%eax
0x00401508 <+8>: mov $0x0,%edx
0x0040150d <+13>: pop %ebp
0x0040150e <+14>: ret
End of assembler dump.
3、 超long long long long
ecx参战的感觉。
用Intel的吧，大家也方便看一点
fun():
0x00401500 <+0>: push ebp
0x00401501 <+1>: mov ebp,esp
0x00401503 <+3>: sub esp,0xc
=> 0x00401506 <+6>: mov eax,0xab33bc40
0x0040150b <+11>: mov edx,0x89119a22
0x00401510 <+16>: mov ecx,0x403b
0x00401515 <+21>: mov DWORD PTR [ebp-0xc],eax
0x00401518 <+24>: mov DWORD PTR [ebp-0x8],edx
0x0040151b <+27>: mov DWORD PTR [ebp-0x4],ecx
0x0040151e <+30>: fld TBYTE PTR [ebp-0xc]
0x00401521 <+33>: leave
0x00401522 <+34>: ret
4、 真· 超long long long long
long128构造函数：
0x00415fb0 <+0>: push ebp
0x00415fb1 <+1>: mov ebp,esp
0x00415fb3 <+3>: sub esp,0x18
0x00415fb6 <+6>: mov DWORD PTR [ebp-0x4],ecx
0x00415fb9 <+9>: mov eax,DWORD PTR [ebp+0x8]
0x00415fbc <+12>: mov DWORD PTR [ebp-0x10],eax
0x00415fbf <+15>: mov eax,DWORD PTR [ebp+0xc]
0x00415fc2 <+18>: mov DWORD PTR [ebp-0xc],eax
0x00415fc5 <+21>: mov eax,DWORD PTR [ebp+0x10]
0x00415fc8 <+24>: mov DWORD PTR [ebp-0x18],eax
0x00415fcb <+27>: mov eax,DWORD PTR [ebp+0x14]
0x00415fce <+30>: mov DWORD PTR [ebp-0x14],eax
0x00415fd1 <+33>: mov ecx,DWORD PTR [ebp-0x4] <== this
0x00415fd4 <+36>: mov eax,DWORD PTR [ebp-0x10]
0x00415fd7 <+39>: mov edx,DWORD PTR [ebp-0xc]
0x00415fda <+42>: mov DWORD PTR [ecx],eax <== eax, edx合起来就是一个long long
0x00415fdc <+44>: mov DWORD PTR [ecx+0x4],edx
0x00415fdf <+47>: mov ecx,DWORD PTR [ebp-0x4]
0x00415fe2 <+50>: mov eax,DWORD PTR [ebp-0x18]
0x00415fe5 <+53>: mov edx,DWORD PTR [ebp-0x14]
0x00415fe8 <+56>: mov DWORD PTR [ecx+0x8],eax <== 同上，另一个赋值操作
0x00415feb <+59>: mov DWORD PTR [ecx+0xc],edx
=> 0x00415fee <+62>: leave
0x00415fef <+63>: ret 0x10
fun():
0x00401500 <+0>: push ebp
0x00401501 <+1>: mov ebp,esp
0x00401503 <+3>: sub esp,0x10 <==本地的缓冲区
0x00401506 <+6>: mov DWORD PTR [esp+0x8],0x44332211
0x0040150e <+14>: mov DWORD PTR [esp+0xc],0x88776655
0x00401516 <+22>: mov DWORD PTR [esp],0x55667788
0x0040151d <+29>: mov DWORD PTR [esp+0x4],0x11223344 <==把这几个倒霉数字存进去
0x00401525 <+37>: mov ecx,DWORD PTR [ebp+0x8] <==ebp+0x8，这个临时的long128变量地址
0x00401528 <+40>: call 0x415fb0 <long128::long128(long long, long long)>
0x0040152d <+45>: sub esp,0x10 <==栈上的缓冲区释放掉
=> 0x00401530 <+48>: mov eax,DWORD PTR [ebp+0x8] <==变量的地址返回eax……
0x00401533 <+51>: leave
0x00401534 <+52>: ret
main():
0x00401535 <+0>: push ebp
0x00401536 <+1>: mov ebp,esp
0x00401538 <+3>: and esp,0xfffffff0
0x0040153b <+6>: sub esp,0x20
0x0040153e <+9>: call 0x409680 <__main>
0x00401543 <+14>: lea eax,[esp+0x10] <==long128的内存
0x00401547 <+18>: mov DWORD PTR [esp],eax
0x0040154a <+21>: call 0x401500 <fun()> <==别忘了这时候已经赋值给long128 tempA了
=> 0x0040154f <+26>: mov eax,0x0 <== return 0;
0x00401554 <+31>: leave
0x00401555 <+32>: ret
call = push + jmp，
esp => [ EAX ]
aftercall:
esp => [ retnaddr ]
[ EAX ]
1st instruction:
esp => [ ebp ]
[ retnaddr ]
[ EAX ] <= esp+8
上一层预留空间了，学会废物利用了。
5、假·超long long long long
fun():
0x00401500 <+0>: push ebp
0x00401501 <+1>: mov ebp,esp
=> 0x00401503 <+3>: mov eax,DWORD PTR [ebp+0x8] <==long128的地址
0x00401506 <+6>: mov DWORD PTR [eax],0x55667788 <==第一次赋值
0x0040150c <+12>: mov DWORD PTR [eax+0x4],0x11223344
0x00401513 <+19>: mov eax,DWORD PTR [ebp+0x8]
0x00401516 <+22>: mov DWORD PTR [eax+0x8],0x44332211 <==第二次赋值
0x0040151d <+29>: mov DWORD PTR [eax+0xc],0x88776655
0x00401524 <+36>: nop
0x00401525 <+37>: mov eax,DWORD PTR [ebp+0x8]
0x00401528 <+40>: pop ebp
0x00401529 <+41>: ret
main()：
0x0040152a <+0>: push ebp
0x0040152b <+1>: mov ebp,esp
0x0040152d <+3>: and esp,0xfffffff0
0x00401530 <+6>: sub esp,0x20
0x00401533 <+9>: call 0x409670 <__main>
0x00401538 <+14>: lea eax,[esp+0x10]
0x0040153c <+18>: mov DWORD PTR [esp],eax
0x0040153f <+21>: call 0x401500 <fun()>
=> 0x00401544 <+26>: mov eax,0x0
0x00401549 <+31>: leave
0x0040154a <+32>: ret
看来跟之前一样。
6、 terminated
多加一句varA.h1++;
0x0040152a <+0>: push ebp
0x0040152b <+1>: mov ebp,esp
0x0040152d <+3>: and esp,0xfffffff0
0x00401530 <+6>: sub esp,0x20
0x00401533 <+9>: call 0x409680 <__main>
=> 0x00401538 <+14>: lea eax,[esp+0x10]
0x0040153c <+18>: mov DWORD PTR [esp],eax
0x0040153f <+21>: call 0x401500 <fun()>
0x00401544 <+26>: mov eax,DWORD PTR [esp+0x10]
0x00401548 <+30>: mov edx,DWORD PTR [esp+0x14]
0x0040154c <+34>: add eax,0x1
0x0040154f <+37>: adc edx,0x0
0x00401552 <+40>: mov DWORD PTR [esp+0x10],eax
0x00401556 <+44>: mov DWORD PTR [esp+0x14],edx
0x0040155a <+48>: mov eax,0x0
0x0040155f <+53>: leave
0x00401560 <+54>: ret
ok done.有空再研究研究其他的。
给开发板装了一个postgre，可是启动的时候问题多多
Options marked [*] produce a lot of output - pipe it through `less' or `more' !
pi@BLASTN2 ~ :( $ sudo dpkg --configure postgresql-9.1 postgre-contrib-9.1
Setting up postgresql-9.1 (9.1.14-0+deb7u1) ...
[....] Starting PostgreSQL 9.1 database server: main[....] The PostgreSQL server failed to start. Please check the log output: 2014-11-13 18:16:55 CST LOG: could not bind IPv6 socket: Cannot assign requested address 2014-11-13 18:16:55 CST HINT: Is another postmaster already running on port 5432? If not, wait a few seconds and retry. 2014-11-13 18:16:55 CST WARNING: could not create listen socket for "localhost" 2014-11-13 18:16:55 CST FATAL: cou[FAILt create any TCP/IP sockets ... failed!
failed!
invoke-rc.d: initscript postgresql, action "start" failed.
dpkg: error processing postgresql-9.1 (--configure):
subprocess installed post-installation script returned error exit status 1
dpkg: error processing postgre-contrib-9.1 (--configure):
no package named `postgre-contrib-9.1' is installed, cannot configure
Errors were encountered while processing:
postgresql-9.1
postgre-contrib-9.1
pi@BLASTN2 ~ :( $ ps aux|grep postgre
pi 23286 0.0 0.0 3648 716 pts/0 S+ 18:19 0:00 grep --colour=auto postgre
提示5432可能被占用，但是仔细看了看端口也没被占用啊
pi@BLASTN2 ~ :( $ sudo netstat -apn|
......
unix 3 [ ] STREAM CONNECTED 3639 2266/dbus-daemon /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 3638 2400/gdm3
unix 3 [ ] STREAM CONNECTED 3626 2266/dbus-daemon /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 3625 2349/NetworkManager
unix 3 [ ] STREAM CONNECTED 3614 2266/dbus-daemon /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 3613 2354/bluetoothd
unix 3 [ ] STREAM CONNECTED 3610 2266/dbus-daemon /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 2914 2349/NetworkManager
unix 3 [ ] STREAM CONNECTED 3556 2266/dbus-daemon /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 3555 2303/avahi-daemon:
unix 3 [ ] STREAM CONNECTED 3549 2304/avahi-daemon:
unix 3 [ ] STREAM CONNECTED 3548 2303/avahi-daemon:
unix 3 [ ] STREAM CONNECTED 2872 2266/dbus-daemon
unix 3 [ ] STREAM CONNECTED 2871 2266/dbus-daemon
unix 3 [ ] DGRAM 484 199/udevd
unix 3 [ ] DGRAM 483 199/udevd
pi@BLASTN2 ~ $ sudo netstat -apn>>~/temp.log
看看log，然后试试看ping 127.0.0.1，what's the fuck
pi@BLASTN2 ~ $ ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
^C
--- localhost ping statistics ---
9 packets transmitted, 0 received, 100% packet loss, time 8005ms
pi@BLASTN2 ~ :( $ ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
^C
--- 127.0.0.1 ping statistics ---
61 packets transmitted, 0 received, 100% packet loss, time 60001ms
pi@BLASTN2 ~ :( $ sudo ifconfig -a
eth0 Link encap:Ethernet HWaddr 02:41:0a:81:93:a9
inet addr:192.168.0.109 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::41:aff:fe81:93a9/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:247688 errors:0 dropped:0 overruns:0 frame:0
TX packets:387753 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:80379923 (76.6 MiB) TX bytes:406363850 (387.5 MiB)
Interrupt:117 Base address:0xc000
lo Link encap:Local Loopback
LOOPBACK MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
tunl0 Link encap:IPIP Tunnel HWaddr
NOARP MTU:1480 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
解决方案：
保存之后，
$ sudo ifconfig eth0 down
$ sudo ifconfig eth0 up
或者干脆直接
$ sudo reboot
再来ping一次，可以ping通。
pi@BLASTN2 ~ :( $ file /usr/lib/arm-linux-gnueabihf/libxml2.so.2
/usr/lib/arm-linux-gnueabihf/libxml2.so.2: symbolic link to `libxml2.so.2.8.0'
pi@BLASTN2 ~ $ file /usr/lib/arm-linux-gnueabihf/libxml2.so.2.8.0
/usr/lib/arm-linux-gnueabihf/libxml2.so.2.8.0: ELF 32-bit LSB shared object, ARM, version 1 (SYSV), dynamically linked, BuildID[sha1]=0x44c6070a41ab03bd54581e371d529871ebf91e77, stripped
pi@BLASTN2 ~ $
pi@BLASTN2 ~ :( $ ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_req=1 ttl=64 time=0.155 ms
64 bytes from 127.0.0.1: icmp_req=2 ttl=64 time=0.101 ms
64 bytes from 127.0.0.1: icmp_req=3 ttl=64 time=0.113 ms
^C
--- 127.0.0.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1998ms
rtt min/avg/max/mdev = 0.101/0.123/0.155/0.023 ms
可是奇葩的是obconf失败了，所有窗口都没标题栏了。。。一看提示
error while loading shared libraries: /lib/libxml2.so.2: invalid ELF header
and
(obconf:3513): GdkPixbuf-CRITICAL **: gdk_pixbuf_copy_area: assertion `src_pixbuf != NULL' failed
/lib/arm-linux-gnueabihf/libgcrypt.so.11: invalid ELF header
Failed to load module: /usr/lib/arm-linux-gnueabihf/gio/modules/libgiognutls.so
pi@BLASTN2 ~ $ sudo apt-get install libgcrypt-dev --reinstall
[sudo] password for pi:
^Cpi@BLASTN2 ~ :( $ sudo apt-get install libgcrypt-dev --reinstall
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libgcrypt11-dev' instead of 'libgcrypt-dev'
The following packages were automatically installed and are no longer required:
libmozjs24d xulrunner-24.0
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0 B/383 kB of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 186234 files and directories currently installed.)
Preparing to replace libgcrypt11-dev 1.5.0-5+deb7u2 (using .../libgcrypt11-dev_1.5.0-5+deb7u2_armhf.deb) ...
Unpacking replacement libgcrypt11-dev ...
Processing triggers for man-db ...
Setting up libgcrypt11-dev (1.5.0-5+deb7u2) ...
dafuq？啥玩意儿，file一下结果居然是ISO-8859-TEXT，我操，说好的库呢，干脆重装一次得了，
$ sudo apt-get -f install obconf
$ sudo apt-get install obconf --reinstall
$ sudo reboot
ok, done。其实猜测是因为之前用了错的opera源导致的，这个一般都是32、64以及arm的库弄混了的原因。待会儿清个源。
然后，虽然这个没问题了，但是libcrypt.so.11还是有同样的问题，浏览器起不了，reinstall libgcrypt11-dev无果，拷贝debug下的更是不行，直接报segment fault。
pi@BLASTN2 ~ :( $ netsurf-gtk
netsurf-gtk: error while loading shared libraries: /lib/arm-linux-gnueabihf/libgcrypt.so.11: invalid ELF header
pi@BLASTN2 ~ :( $ file /lib/arm-linux-gnueabihf/libgcrypt.so.11
/lib/arm-linux-gnueabihf/libgcrypt.so.11: symbolic link to `libgcrypt.so.11.7.0'
pi@BLASTN2 ~ $ file /lib/arm-linux-gnueabihf/libgcrypt.so.11.7.0
/lib/arm-linux-gnueabihf/libgcrypt.so.11.7.0: ISO-8859 text, with very long lines, with no line terminators
pi@BLASTN2 ~ $
只好祭出大杀器。
附上so文件，用自带的传输功能传的，信得过就下吧，自己改名回去：
http://www.nul.pw/usr/uploads/2014/12/595411591.png
注意，如果你缺这个文件，连wget curl都是启动不了的，如果是远程机器，自求多福如果开了啥samba sftp ftp之类的还可以一拼= =，物理机器就靠u盘吧。
修完了真是开心啊，postgre？去你的，不装了- -
不下两分钟已经弄崩四五次了，出现这么个栈调用，大家也都知道是什么情况了吧：
0:000> kvn
# ChildEBP RetAddr Args to Child
00 00128688 7c92de5c 7c801e3a ffffffff c0000409 ntdll!KiFastSystemCallRet (FPO: [0,0,0])
01 0012868c 7c801e3a ffffffff c0000409 001289d4 ntdll!ZwTerminateProcess+0xc (FPO: [2,0,0])
02 0012869c 004c9453 ffffffff c0000409 310a3291 kernel32!TerminateProcess+0x20 (FPO: [Non-Fpo])
WARNING: Stack unwind information not available. Following frames may be wrong.
03 001289d4 004712e9 0000011e 0324028a 00000109 360zip+0xc9453