C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  strtok segfaults in CLI but not in GDB          C++Talk.NET Forum Index -> C Language View previous topic :: View next topic   Author Message Pietro Cerutti Guest Posted: Wed May 16, 2007 9:11 am    Post subject: strtok segfaults in CLI but not in GDB Hello, here I have a strange problem with a real simple strtok example. The program is as follows: ### BEGIN STRTOK ### #include <string.h> #include <stdio.h> int main() { char *input1 = "Hello, World!"; char *tok; tok = strtok(input1, " "); if(tok) printf("%s\n", tok); tok = strtok(NULL, " "); if(tok) printf("%s\n", tok); return(0); } ### END STRTOK ### Now, when I run it from the command line, I get a bus error: ### BEGIN COMMAND LINE OUTPUT ### Quote: gcc -ggdb -Wall -o strtok strtok.c ./strtok Bus error (core dumped) Exit 138 ### END COMMAND LINE OUTPUT ### When I run it step by step in GDB, the program terminates normally: ### BEGIN DEBUGGER OUTPUT ### Quote: gdb ./strtok GNU gdb 6.1.1 [FreeBSD] [snip]GDB copyright and bla bla[/snip] (gdb) break main Breakpoint 1 at 0x8048570: file strtok.c, line 6. (gdb) run Starting program: /home/piter/strtok Breakpoint 1, main () at strtok.c:6 6 char *input1 = "Hello, World!"; (gdb) next 10 tok = strtok(input1, " "); (gdb) 11 if(tok) printf("%s\n", tok); (gdb) Hello, 13 tok = strtok(NULL, " "); (gdb) 14 if(tok) printf("%s\n", tok); (gdb) World! 16 return(0); (gdb) 18 } (gdb) 0x08048485 in _start () (gdb) Single stepping until exit from function _start, which has no line number information. Program exited normally. (gdb) ### END DEBUGGER OUTPUT ### Is there something I'm missing wrt C and/or strtok, or it's rather a problem related to my environment (in which case I'll be happy to post in the right newsgroup) ? Thanx in advance -- Pietro Cerutti PGP Public Key ID: http://gahr.ch/pgp Back to top Ian Collins Guest Posted: Wed May 16, 2007 9:11 am    Post subject: Re: strtok segfaults in CLI but not in GDB Pietro Cerutti wrote: Quote: Hello, here I have a strange problem with a real simple strtok example. The program is as follows: ### BEGIN STRTOK ### #include <string.h #include <stdio.h int main() { char *input1 = "Hello, World!"; char *tok; tok = strtok(input1, " "); strtok alters its input. You are passing it a string literal, modifying a string literal invokes the demons of undefined behavior. Don't. -- Ian Collins. Back to top Richard Heathfield Guest Posted: Wed May 16, 2007 9:12 am    Post subject: Re: strtok segfaults in CLI but not in GDB Pietro Cerutti said: Quote: Hello, here I have a strange problem with a real simple strtok example. The program is as follows: ### BEGIN STRTOK ### #include <string.h #include <stdio.h int main() { char *input1 = "Hello, World!"; char *tok; tok = strtok(input1, " "); strtok modifies the string you pass it. You pass it a string literal. You're not allowed to modify string literals. Change char *input1 = "Hello, World!"; to char input1[] = "Hello, World!"; -- Richard Heathfield "Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk email: rjh at the above domain, - www. Back to top CBFalconer Guest Posted: Thu May 17, 2007 8:48 am    Post subject: Re: strtok segfaults in CLI but not in GDB Pietro Cerutti wrote: Quote: Chris Dollin wrote: You're not allowed to write into a string literal: that gets you undefined behaviour. An implementation may just write into the string. Uh? So you mean that a string literal isn't unmodifiable by definition? Undefined behaviour includes working the way you think i should. -- <http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.txt> <http://www.securityfocus.com/columnists/423> <http://www.aaxnet.com/editor/edit043.html> <http://kadaitcha.cx/vista/dogsbreakfast/index.html> cbfalconer at maineline dot net -- Posted via a free Usenet account from http://www.teranews.com Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C Language All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.