so strange
I moved that function definition from source file to header file, it built normally.
but when it ran, "Segmentation fault" came again..
I did as axeljaeger said, got things as follow:
warning: (Internal error: pc 0x46e1a1 in read in psymtab, but not in symtab.)


Program received signal SIGSEGV, Segmentation fault.
0x02ac3f93 in strlen () from /lib/tls/i686/cmov/libc.so.6
(gdb) backtrace
#0 0x02ac3f93 in strlen () from /lib/tls/i686/cmov/libc.so.6
#1 0x02c684ff in XSetCommand () from /usr/lib/libX11.so.6
#2 0x02c6cf51 in XSetWMProperties () from /usr/lib/libX11.so.6
#3 0x06d73134 in QWidgetPrivate::create_sys (this=0x83782d0, window=0, initializeWindow=true, destroyOldWindow=true)
at /var/tmp/qt-src/src/gui/kernel/qwidget_x11.cpp:795
#4 0x06d2bb21 in QWidget::create (this=0xbffff1ec, window=0, initializeWindow=true, destroyOldWindow=true)
at /var/tmp/qt-src/src/gui/kernel/qwidget.cpp:1319
#5 0x06d2e7b1 in QWidget::setVisible (this=0xbffff1ec, visible=true) at /var/tmp/qt-src/src/gui/kernel/qwidget.cpp:7353
#6 0x081730f0 in QWidget::show (this=0xbffff1ec) at /usr/local/qt-4.6.2/qt/include/QtGui/qwidget.h:485
#7 0x00bc827d in PadSystem::PadSplashScreen::show (this=0xbffff1ec) at src/PadSplashScreen.cpp:58
#8 0x08223a46 in main (argc=1, argv=0xbffff304) at main.cpp:66
(gdb)