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Groups > comp.lang.c > #386044
| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Whaddaya think? |
| Date | 2024-06-16 17:06 -0700 |
| Organization | None to speak of |
| Message-ID | <87ed8w3025.fsf@nosuchdomain.example.com> (permalink) |
| References | (2 earlier) <v4lm16$3s87h$4@dont-email.me> <v4lmso$3sl7n$1@dont-email.me> <v4lr0m$3tbpj$1@dont-email.me> <8734pd4g3s.fsf@nosuchdomain.example.com> <v4ltuj$3trj2$1@dont-email.me> |
Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
[...]
> #include <stdlib.h>
> #include <stdio.h>
>
> void main (int argc, char * argv[])
> {
> int chunk = 10;
> int bufsize = chunk+1;
> char * buf = malloc(bufsize);
> char * anchor = buf;
> while (fgets(buf, chunk+1, stdin) != NULL)
> if (realloc(anchor, bufsize += chunk) != NULL)
> buf += chunk;
> puts(anchor);
> }
realloc() can return the pointer you pass to it if there's enough room
in the existing location. (Or it can relocate the buffer even if there
is enough room.)
But if realloc() moves the buffer (copying the existing data to it), it
returns a pointer to the new location and invalidates the old one. You
discard the new pointer, only comparing it to NULL.
Perhaps you assumed that realloc() always expands the buffer in place.
It doesn't.
If the above program worked for you, I suspect that either realloc()
never relocated the buffer, or you continued using the original buffer
(and beyond) after realloc() invalidated it.
The worst consequence of undefined behavior is having your code appear
to "work".
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */
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Whaddaya think? DFS <nospam@dfs.com> - 2024-06-15 15:36 -0400
Re: Whaddaya think? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-15 22:33 +0100
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Re: Whaddaya think? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-17 00:17 +0100
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 08:49 -0400
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-15 15:22 -0700
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-16 12:20 -0400
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-16 13:54 -0700
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-16 22:41 -0400
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-16 22:45 -0700
Re: Whaddaya think? Kaz Kylheku <643-408-1753@kylheku.com> - 2024-06-17 07:39 +0000
Re: Whaddaya think? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-17 01:22 -0700
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 09:50 -0400
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Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-22 17:10 -0700
Re: Whaddaya think? Phil Carmody <pc+usenet@asdf.org> - 2024-06-23 11:20 +0300
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-18 00:19 -0700
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 03:10 -0700
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-18 17:24 -0700
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 17:55 -0700
Re: Whaddaya think? Kaz Kylheku <643-408-1753@kylheku.com> - 2024-06-19 01:58 +0000
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 08:50 -0400
Re: Whaddaya think? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-17 15:41 +0100
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-18 08:12 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 03:07 -0700
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-17 00:30 -0400
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-16 01:56 +0300
Re: Whaddaya think? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-06-16 03:26 +0000
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 05:41 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-15 21:17 -0700
Re: Whaddaya think? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-06-16 04:41 +0000
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 06:44 +0200
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-16 11:09 -0400
Re: Whaddaya think? David Brown <david.brown@hesbynett.no> - 2024-06-16 17:56 +0200
Re: Whaddaya think? bart <bc@freeuk.com> - 2024-06-16 18:14 +0100
Re: Whaddaya think? David Brown <david.brown@hesbynett.no> - 2024-06-17 14:44 +0200
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 09:52 -0400
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 06:51 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-15 22:21 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 07:41 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-15 22:49 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 11:29 +0200
Re: Whaddaya think? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-16 16:04 +0100
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 17:13 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-16 13:32 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 07:41 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-16 23:20 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 09:16 +0200
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-17 09:38 -0400
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-17 16:17 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-18 07:09 +0200
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-18 03:25 -0400
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 02:57 -0700
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-17 16:15 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-18 08:02 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 19:07 -0700
Re: Whaddaya think? David Brown <david.brown@hesbynett.no> - 2024-06-19 09:50 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-19 13:13 -0700
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-17 02:21 -0400
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 09:22 +0200
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-16 11:11 +0300
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 11:07 +0200
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-16 12:38 +0300
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 12:03 +0200
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-16 14:31 +0300
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 17:37 +0200
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-17 00:45 +0300
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-16 17:06 -0700
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-16 22:40 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 07:52 +0200
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 09:45 -0400
Re: Whaddaya think? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-17 13:16 -0700
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-17 17:07 -0400
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-17 15:48 -0700
Re: Whaddaya think? scott@slp53.sl.home (Scott Lurndal) - 2024-06-17 22:48 +0000
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-17 15:44 -0700
Re: Whaddaya think? David Brown <david.brown@hesbynett.no> - 2024-06-18 15:00 +0200
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-18 06:57 +0200
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-18 00:25 -0700
Re: Whaddaya think? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-17 02:38 -0400
Re: Whaddaya think? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-18 17:01 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 07:48 +0200
Re: Whaddaya think? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-16 23:29 -0700
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-17 09:35 +0200
Re: Whaddaya think? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-16 08:19 +0100
Re: Whaddaya think? Michael S <already5chosen@yahoo.com> - 2024-06-16 10:44 +0300
Re: Whaddaya think? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-16 11:13 +0200
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-16 11:03 -0400
Re: Whaddaya think? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2024-06-16 15:52 +0000
Re: Whaddaya think? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-16 17:17 +0100
Re: Whaddaya think? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-06-18 08:06 +0000
Re: Whaddaya think? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2024-06-25 17:37 +0000
Re: Whaddaya think? DFS <nospam@dfs.com> - 2024-06-25 14:09 -0400
Re: Whaddaya think? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2024-06-25 18:11 +0000
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