August 2011 Archives

    libtools生成so的时候，发现在rhel5.3和fedora15下，结果竟然不一样，Makefile.am这样写道：

dydir    = $(bindir)/pwd
dy_PROGRAMS    = libdy.so
libdy_so_SOURCES = dy.cpp dy.h
libdy_so_CXXFLAGS = -fPIC
libdy_so_LDFLAGS = -shared -fpic

在fedora15下，这里面dy.cpp里面必须包括main函数，否则编译不过，而rhel5.3则没有这个问题，查了过程发现fedora15和rhel5.3的编译过程分别如下所示：

fedora15：
/bin/sh ../../../libtool --tag=CXX   --mode=link g++ -fPIC -g -O2 -shared -fpic  -o libdy.so libdy_so-dy.o 
libtool: link: g++ -fPIC -g -O2 -fpic -o libdy.so libdy_so-dy.o
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status

和

rhel5.3
/bin/sh ../../../libtool --tag=CXX --mode=link g++  -g -O2   -o libdy.so -shared -fpic libdy_so-dy.o 
g++ -g -O2 -o libdy.so -shared -fpic libdy_so-dy.o

应该是libtool在fedora15上丢失了-shared参数所致，fedora15的libtool版本为2.4，而rhel5.3的libtool版本为1.5.22。

    一般使用ssh -X连接到服务器，启动xclock，发现并没有窗口弹出，并提示错误信息：

Error: Can't open display:

    以为是Xserver的问题，比较环境变量DISPLAY以及Xorg的一些配置，也没有找到原因。
    后来想到以前俺博客当中应该有相关的资料，但忽略了ssh的服务器配置，其实解决的问题很简单，当想通过XServer显示服务器上的UI程序时，需要在ssh的时候加上-X参数外，还需要服务器的sshd支持远程的XServer，其/etc/ssh/ssh_config配置如下：

#    $OpenBSD: ssh_config,v 1.23 2007/06/08 04:40:40 pvalchev Exp $

# This is the ssh client system-wide configuration file.  See
# ssh_config(5) for more information.  This file provides defaults for
# users, and the values can be changed in per-user configuration files
# or on the command line.

# Configuration data is parsed as follows:
#  1. command line options
#  2. user-specific file
#  3. system-wide file
# Any configuration value is only changed the first time it is set.
# Thus, host-specific definitions should be at the beginning of the
# configuration file, and defaults at the end.

# Site-wide defaults for some commonly used options.  For a comprehensive
# list of available options, their meanings and defaults, please see the
# ssh_config(5) man page.

# Host *
#   ForwardAgent no
ForwardX11 yes
#   RhostsRSAAuthentication no
#   RSAAuthentication yes
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   BatchMode no
#   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/identity
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   Port 22
#   Protocol 2,1
#   Cipher 3des
#   Ciphers aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc
#   MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
StrictHostKeyChecking no
UserKnownHostsFile /dev/null
LogLevel error