C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Array of Pointers and Freeing problem          C++Talk.NET Forum Index -> C Language View previous topic :: View next topic   Author Message Guest Posted: Sat May 12, 2007 9:11 am    Post subject: Array of Pointers and Freeing problem hi, Following is problematic Code main() { char *ptr[1]={NULL}; ftn(ptr); } void ftn(**data) { *data=malloc(4); memset(*data,0,4); strcpy(*data,"HAI"); } Back to top Richard Heathfield Guest Posted: Sat May 12, 2007 9:11 am    Post subject: Re: Array of Pointers and Freeing problem anand1603 (AT) yahoo (DOT) com said: Quote: hi, Following is problematic Code main() { char *ptr[1]={NULL}; ftn(ptr); } void ftn(**data) { *data=malloc(4); memset(*data,0,4); strcpy(*data,"HAI"); } This won't compile either. -- 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 Ian Collins Guest Posted: Sat May 12, 2007 9:11 am    Post subject: Re: Array of Pointers and Freeing problem anand1603 (AT) yahoo (DOT) com wrote: Quote: hi, Following is problematic Code Indeed it is, it won't compile. Quote: main() { char *ptr[1]={NULL}; ftn(ptr); } void ftn(**data) { *data=malloc(4); memset(*data,0,4); strcpy(*data,"HAI"); } -- Ian Collins. Back to top Martin Ambuhl Guest Posted: Sat May 12, 2007 9:11 am    Post subject: Re: Array of Pointers and Freeing problem anand1603 (AT) yahoo (DOT) com wrote: Quote: hi, Following is problematic Code Yes, it is. Start by paying attention to the following changes. Then decide what I have left undone. /* You need these headers */ #include <stdlib.h> #include <string.h> /* Without the following, ftn (in main) is explicitly declared to return an int, which conflicts with its later redefinition */ void ftn(char *data[]); /* main returns an int. You should say so. Not doing so is an error for the C standard from 1999 on, and a bad idea for the earlier standard. */ int main(void) { char *ptr[1] = { NULL }; ftn(ptr); /* You allocated space for ptr[0] to point at. free it */ free(*ptr); /* main returns an int. You should do so. Not doing so is an error for the C standard up to 1999, and a bad idea for the later standard. */ return 0; } /* You have specified no type for the argument to ftn, do so: */ void ftn(char *data[]) { *data = malloc(4); /* you should always check that malloc succeeds */ if (!*data) return; #if 0 /* The following memset is completely worthless. It has been commented out. */ memset(*data, 0, 4); #endif strcpy(*data, "HAI"); } Back to top Barry Schwarz Guest Posted: Sun May 13, 2007 5:03 am    Post subject: Re: Array of Pointers and Freeing problem On Sat, 12 May 2007 18:07:04 -0400, CBFalconer <cbfalconer (AT) yahoo (DOT) com> wrote: Quote: Richard Heathfield wrote: anand1603 (AT) yahoo (DOT) com said: Following is problematic Code main() { char *ptr[1]={NULL}; ftn(ptr); } void ftn(**data) { *data=malloc(4); memset(*data,0,4); strcpy(*data,"HAI"); } This won't compile either. However, this will (untested). (To OP) Study the difference. #include <stdlib.h #include <string.h void ftn(**data) { Doesn't the argument need a type? I think you meant void ftn(char **data){ Quote: *data = malloc(4); memset(*data, 0, 4); strcpy(*data, "HAI"); } int main(void) { char *ptr[1] = {NULL}; ftn(ptr); return 0; } Remove del for email Back to top        C++Talk.NET Forum Index -> C Language All times are GMT Page 1 of 1 Powered by phpBB © 2001, 2006 phpBB Group