#include <stdio.h>
#include <stdlib.h>
//WARNING: The function's signature should be: f( int ** )
void f(int *ip) {
static int dummy = 5;
*ip = &dummy;
}
int main(){
int *ip;
f(&ip);
printf("%d",*ip );
return 0;
}
The function's signature should be: f( int ** ). However, f( int *) seems to
produce the same results, even though I am
warned by the compiler (Borland_bcc_5. 5):
Warning W8069 solution.c 5: Nonportable pointer conversion in function f
Warning W8075 solution.c 12: Suspicious pointer conversion in function main
What can go wrong when you pass the address of a pointer to a function that
does not recieve a pointer to a pointer?
TIA
jimjim
Mar 25 '06
16  3167 
# The question was posted by "jimjim" <ne*****@blueyo nder.co.uk>.
# Please don't snip attributions. And *please* stop using your stupid
# '#' quoting character. You've been told repeatedly that it causes
# problems for some newsreaders; your stubbornness on this point is why
# I usually ignore anything you post.
Now I'm scared. Please, please, don't netkop me.
# Casting to suppress compiler warnings is dangerous and foolish.
# Parameters of different types can be passed by different mechanisms,
# even if they're the same size. For example, some systems might use
# different sets of registers for pointers vs. integers, or integers
If your compiler is incapable of moving values into correct registers
during a cast, you desperately need a new compiler.
--
SM Ryan http://www.rawbw.com/~wyrmwif/
This is one wacky game show.
SM Ryan wrote: The question was posted by "jimjim" <ne*****@blueyo nder.co.uk>.
Please don't snip attributions. And *please* stop using your stupid
'#' quoting character. You've been told repeatedly that it causes
problems for some newsreaders; your stubbornness on this point is why
I usually ignore anything you post.
Now I'm scared. Please, please, don't netkop me.
Casting to suppress compiler warnings is dangerous and foolish.
Parameters of different types can be passed by different mechanisms,
even if they're the same size. For example, some systems might use
different sets of registers for pointers vs. integers, or integers
If your compiler is incapable of moving values into correct registers
during a cast, you desperately need a new compiler.
The whole point of a cast is to force a compiler to do what you want it
to do, in which case it might very well end up storing values in
registers not suited for their types, and giving rise to undefined
behaviour. That is why it's advisable to use a cast only after
understanding the ramifications, (which might mean looking up
implementation specific behaviour), and when it's use is essential to
the code in question.
SM Ryan <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> writes:
[...] Casting to suppress compiler warnings is dangerous and foolish.
Parameters of different types can be passed by different mechanisms,
even if they're the same size. For example, some systems might use
different sets of registers for pointers vs. integers, or integers
If your compiler is incapable of moving values into correct registers
during a cast, you desperately need a new compiler.
Ok, the differences in parameter passing applies mostly in cases where
a call is performed with no prototype in scope.
The original code has a function that takes a parameter of type int*,
and calls it with an argument of type int**. The compiler quite
correctly complained (it's a constraint violation, so it's required to
do so).
The solution is to fix either the function or the call so the types
are consistent. Casting the int** argument to int* will (probably)
silence the warning, and won't cause problems with parameter passing
mechanisms. The only problem is that the result of converting the
int** value to int* is unlikely to be meaningful.
The OP asked what can go wrong; you advised him to hide the problem
with a meaningless cast.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
"SM Ryan" <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> wrote in
message news:12******** *****@corp.supe rnews.com... # The question was posted by "jimjim" <ne*****@blueyo nder.co.uk>.
# Please don't snip attributions. And *please* stop using your stupid
# '#' quoting character. You've been told repeatedly that it causes
# problems for some newsreaders; your stubbornness on this point is why
# I usually ignore anything you post.
Now I'm scared. Please, please, don't netkop me.
Keith. How can you criticize him for "#" when you use "]" on occasion?
"Rod Pemberton" <do*********@so rry.bitbuck.cmm > writes: "SM Ryan" <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> wrote in
message news:12******** *****@corp.supe rnews.com... # The question was posted by "jimjim" <ne*****@blueyo nder.co.uk>.
# Please don't snip attributions. And *please* stop using your stupid
# '#' quoting character. You've been told repeatedly that it causes
# problems for some newsreaders; your stubbornness on this point is why
# I usually ignore anything you post.
Now I'm scared. Please, please, don't netkop me.
Keith. How can you criticize him for "#" when you use "]" on occasion?
I use "]" only when I'm quoting something that doesn't come directly
from the parent article; using ">" in that context could be
misleading. I've never heard of any newsreader having problems with
"]" (if you know of one that does, please let me know). Multiple
people have said that "#" does cause problems. It can be argued that
that's a bug in those newsreaders, but I see no point in deliberately
and repeatedly triggering that bug. (In my own newsreader, it's not
much of a problem, except that the command to re-fill a paragraph
doesn't recognize a leading "#" as a quoting character; it does
recognize both ">" and "]".)
SM Ryan has been asked repeatedly why he insists on using "#"; he has
never answered. I can only assume he's being deliberately obnoxious,
which is why I usually ignore him. (I usually try to ignore you as
well, but this was actually a reasonable question.)
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
On Mon, 27 Mar 2006 20:33:34 GMT, in comp.lang.c , Keith Thompson
<ks***@mib.or g> wrote: SM Ryan has been asked repeatedly why he insists on using "#"; he has
never answered.
Actually, I recall that he did. He said at one point that he'd written
his own newsreader and deliberately designed it to use this character
for quotes for an unknown reason. When challenged, he got stroppy and
said everyone else's s/w was broken. Go figure...
Mark McIntyre
--
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan
On 2006-03-27, Keith Thompson <ks***@mib.or g> wrote: "Rod Pemberton" <do*********@so rry.bitbuck.cmm > writes: "SM Ryan" <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> wrote in
message news:12******** *****@corp.supe rnews.com... # The question was posted by "jimjim" <ne*****@blueyo nder.co.uk>.
# Please don't snip attributions. And *please* stop using your stupid
# '#' quoting character. You've been told repeatedly that it causes
# problems for some newsreaders; your stubbornness on this point is why
# I usually ignore anything you post.
Now I'm scared. Please, please, don't netkop me.
Keith. How can you criticize him for "#" when you use "]" on occasion?
I use "]" only when I'm quoting something that doesn't come directly
from the parent article;
I use | for that purpose, it works better in my newsreader.
using ">" in that context could be misleading. I've never heard of
any newsreader having problems with "]" (if you know of one that does,
please let me know).
My editor doesn't allow me to easily reflow text with quote markers
other than > and # by default. However, I have altered the default
setting, and I may alter it further.
Multiple people have said that "#" does cause problems. It can be
argued that that's a bug in those newsreaders, but I see no point in
deliberately and repeatedly triggering that bug.
Which newsreaders are those? Mine doesn't color either # or ] properly,
but I could change that if i cared. oddly, it recognizes = as a quote
marker.
(In my own newsreader, it's not much of a problem, except that the
command to re-fill a paragraph doesn't recognize a leading "#" as
a quoting character; it does recognize both ">" and "]".)
SM Ryan has been asked repeatedly why he insists on using "#"; he has
never answered. I can only assume he's being deliberately obnoxious,
which is why I usually ignore him. (I usually try to ignore you as
well, but this was actually a reasonable question.)
What _does_ it break? It's hard to imagine what that could break, other
than people whining that it doesn't format it as a blockquote in their
gui newsreaders. Do non-quoted lines beginning in # also break them? in
that case, how does it know the difference? What i'm saying is, does it
actually _break_ them, or does it somehow fail to be recognized as
quoted text, and if the latter, is that really worth caring about?
If the newsreader really breakes, like, crashes, or fails to display, on
lines beginning in #, that is a serious bug in the newsreader and there
are much more serious problems than people using it as a quote marker.
If it just doesn't format it or color it or do other special things
based on it being quoted text, that's not really worth giving a crap
about IMO. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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