c - what's the difference between the two code block? -


in program , use basename function partition. first , write if sentence this:

if (!strncmp(buf,      basename("/dev/mmcblk0p3"),      strlen(basename("/dev/mmcblk0p3"))) {     ret = 1; } else {     ret = 0; }

buf point string "mmcblk0p3" , ret = 0, using gdb, found basename("/dev/mmcblk0p3") returned weird string, when changed program this:

char *p = null; p = basename("/dev/mmcblk0p3"); if (!strncmp(buf, p, strlen(p)) {     ret = 1; } else {     ret = 0; }

the ret 1, program runs normal. difference? basename cannot used ? compiling environment armel7v/gcc.

one consequence of using non-reentrant function basename returns string subsequent invocations invalidate prior results. need make copy of return value before making second call, or stop using old value after second call has returned. because basename has 1 internal buffer store result, assuming not modify parameter ( looks case program, because not crash on string literal; still, it's undefined behavior).

modify program follows make portable:

char *p = null; char pathname[] = "/dev/mmcblk0p3"; p = basename(pathname); if (!strncmp(buf, p, strlen(p)) {     ret = 1; } else {     ret = 0; }

Comments

Post a Comment

Popular posts from this blog

jquery - Common JavaScript snippet to share files on Google Drive, Dropbox, Box.net or SkyDrive -

this first assignment of file sharing. need share files our website above mentioned locations. currently, have been exploring each service’s api file sharing. question 1 : there javascript code snippet available (like addthis.com ) share files? question 2 : should use server side coding file sharing or javascript advisable? thanks viewers. found useful plug-in named "ink file picker". saves given http file resource directly users online storage engine. url: https://developers.inkfilepicker.com/docs/web/ live example: http://ctrlq.org/save/
Read more

user interface - Python attempting to create a simple gui, getting "AttributeError: 'MainMenu' object has no attribute 'intro_screen'" -

complete newbie here python started learning language few days ago (with no programming experience beforehand). i'm bashing skull against desk here, trying create 1 menu button lead menu, supposed replace/hide/destroy previous menu (either works, long process can reversed). what i've come far: import wx class mainframe(wx.frame): def __init__(self): wx.frame.__init__(self, none) self.centre() self.main_menu = mainmenu(self) self.intro_screen = introscreen(self) self.intro_screen.hide() class mainmenu(wx.frame): def __init__(self, parent): wx.frame.__init__(self, parent=parent) self.main_menu = mainmenu panel = wx.panel(self) sizer = wx.boxsizer(wx.vertical) nextscreen = wx.button(panel, label='next screen', size=(150,30)) nextscreen.bind(wx.evt_button, self.nextscreen) sizer.add(nextscreen, 0, wx.center|wx.all, 5) self.show() self.c...
Read more

Android Gson.fromJson error -

i've completed tutorial how connect json url , parse content using gson library. code works fine url specified in tutorial, tryed modify work this url . tryed display 1 field second ulr, base field, can't work. here code, please help: public class jsonparsingactivity extends activity { string url = "http://api.openweathermap.org/data/2.5/weather?q=london,uk"; @override public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); inputstream source = retrievestream(url); gson gson = new gson();// main gson class reader reader = new inputstreamreader(source); searchresponse response = gson.fromjson(reader, searchresponse.class); //gson.fromjson(string, class) toast.maketext(this, response.base, toast.length_short).show(); } private inputstream retrievestream(string url) { defaulthttpclient client = new defaulthttpclient(); httpget getrequest = new httpget(url);...
Read more