The C language in the planet Mars

[jacob navia]

Mankind has now two robots wandering about in the planet Mars. No,
it wasn't Mars that invaded Earth, but Earth that landed in Mars
more than two years ago.

After some initial OS glitches (Chris Torek can comment
on those probably) in the Spirit robot, software has done
smoothly ever since.

All the software is written in C, what is a good decision
but also a bad one, C with its warts and all...

In the last two weeks, a software upgrade was sent from
earth to Mars, and the upgrade is scheduled to be
tested this days. Software upgrades take a lot of time
when they are done with several million kilometers
distance!

The Mars Exploration Rover software (MER) is around
650 000 lines of C. The Ames research center developed a
static tester for the software [2] and in 30 minutes
it discovered...

o Un-initialized variable usage
o Returning the address of a local variable (!!!!)
o Overflow in constant expression.

I wonder what kind of compilers does the VXWorks system
use, but almost all compilers I know of will try to
diagnose this kind of errors...

In a news item published in Space daily [1], Green Hills software
boasted that
< quote >
"Green Hills Software Tools Critical To Mars Rover Missions"

Both the "Opportunity" rover, launched July 7, and the "Spirit" rover,
launched June 10, are being directed and controlled by software programs
and systems written with the use of Green Hills development tools.

< end quote >

Green Hills doesn't emit a diagnostic for returning the address of
a local variable?
References:
[1]
http://www.marsdaily.com/reports/Gre..._Missions.html
[2]
http://ic.arc.nasa.gov/researchinfus...S/SMC-IT03.pdf

[Richard Tobin]

In article <44*********************@news.orange.fr>,
jacob navia <ja***@jacob.remcomp.frwrote:

>o Returning the address of a local variable (!!!!)

>Green Hills doesn't emit a diagnostic for returning the address of
a local variable?

I don't know the details of this particular case, but suppose the
code was something like this:

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;
}

How many compilers produce a warning for that?

-- Richard

[jacob navia]

Richard Tobin a écrit :

In article <44*********************@news.orange.fr>,
jacob navia <ja***@jacob.remcomp.frwrote:

>>o Returning the address of a local variable (!!!!)

>>Green Hills doesn't emit a diagnostic for returning the address of
a local variable?

I don't know the details of this particular case, but suppose the
code was something like this:

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;
}

How many compilers produce a warning for that?

-- Richard

Yes, you are right. That would be much more
difficult to find. The other errors are maybe
easier: const overflow can be detected at
compile time.

[Nils Weller]

On 2006-07-23, jacob navia <ja***@jacob.remcomp.frwrote:

Richard Tobin a écrit :

>In article <44*********************@news.orange.fr>,
jacob navia <ja***@jacob.remcomp.frwrote:

>>>o Returning the address of a local variable (!!!!)

>>>Green Hills doesn't emit a diagnostic for returning the address of
a local variable?

I don't know the details of this particular case, but suppose the
code was something like this:

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;
}

How many compilers produce a warning for that?

-- Richard

Yes, you are right. That would be much more
difficult to find.

Hmm, maybe it would be feasible to make this a runtime error. With a
typical stack frame layout, the compiler can easily check whether
returned (non-null) pointer values point into the frame, and if that's
the case terminate the process or call a user-defined error handler or
somesuch.

Probably not worth the cost in general, but could come in handy during
development/debugging.

--
Nils R. Weller, Bremen (Germany)
My real email address is ``nils<at>gnulinux<dot>nl''
.... but I'm not speaking for the Software Libre Foundation!

[spibou]

Richard Tobin wrote:

In article <44*********************@news.orange.fr>,
jacob navia <ja***@jacob.remcomp.frwrote:

o Returning the address of a local variable (!!!!)

Green Hills doesn't emit a diagnostic for returning the address of
a local variable?

I don't know the details of this particular case, but suppose the
code was something like this:

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;
}

How many compilers produce a warning for that?

I decided to do a little experiment with the programme below.

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;

}

int main() {

return 0 ;
}

The Sun compiler , lint on Solaris and gcc -Wall did not
produce any warnings. But splint gave

o.c:8:12: Stack-allocated storage pointer reachable from return value:
pointer
A stack reference is pointed to by an external reference when the
function
returns. The stack-allocated storage is destroyed after the call,
leaving a
dangling reference. (Use -stackref to inhibit warning)
Spiros Bousbouras

[BubbaGump]

On Sun, 23 Jul 2006 10:44:43 +0200, jacob navia
<ja***@jacob.remcomp.frwrote:

>Mankind has now two robots wandering about in the planet Mars. No,
it wasn't Mars that invaded Earth, but Earth that landed in Mars
more than two years ago.

After some initial OS glitches (Chris Torek can comment
on those probably) in the Spirit robot, software has done
smoothly ever since.

All the software is written in C, what is a good decision
but also a bad one, C with its warts and all...

Maybe the problem's with the people writing the language as much as it
is with the language itself. French isn't a bad language just because
monkey's can't speak it.

C is good for anal retentive people who catch most of their own
mistakes. It's apparently not good for normal people.

[Richard Heathfield]

BubbaGump said:

<snip>

>
C is good for anal retentive people who catch most of their own
mistakes.

Are you a qualified psychiatrist, using that term in its medical sense? If
so, please provide evidence to support this.

Or are you just an irksome little jerk who is trying to offend people?

It's apparently not good for normal people.

C is fine for normal people who know how to think. If you don't know how to
think, stay away not just from C, but from programming.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[Ham]

sp****@gmail.com wrote:

>
int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;

}

int main() {

return 0 ;
}

PC-LINT produces the following warning for that piece of code:

diy.c 11 Warning 674: Returning address of auto through
variable 'pointer'.

This example is also a sample violation of MISRA C:2004

[Walter Roberson]

In article <D9********************@bt.com>,
Richard Heathfield <in*****@invalid.invalidwrote:

>BubbaGump said:

>C [...]

>It's apparently not good for normal people.

>C is fine for normal people who know how to think.

There are compelling claims that programmers are not normal people ;-)
--
If you lie to the compiler, it will get its revenge. -- Henry Spencer

[Tak-Shing Chan]

On Tue, 25 Jul 2006, Walter Roberson wrote:

In article <D9********************@bt.com>,
Richard Heathfield <in*****@invalid.invalidwrote:

>BubbaGump said:

>>C [...]

>>It's apparently not good for normal people.

>C is fine for normal people who know how to think.

There are compelling claims that programmers are not normal people ;-)

Indeed. A week or so ago, someone on comp.lang.c wrote,
``Neither is anyone. Normality is a myth. (Do the math. How many
people are normal in every respect?)'' (attribution withheld).

Tak-Shing

[Richard Heathfield]

Tak-Shing Chan said:

On Tue, 25 Jul 2006, Walter Roberson wrote:

>In article <D9********************@bt.com>,
Richard Heathfield <in*****@invalid.invalidwrote:

>>BubbaGump said:

>>>C [...]

>>>It's apparently not good for normal people.

>>C is fine for normal people who know how to think.

There are compelling claims that programmers are not normal people ;-)

Indeed. A week or so ago, someone on comp.lang.c wrote,
``Neither is anyone. Normality is a myth. (Do the math. How many
people are normal in every respect?)'' (attribution withheld).

Touche'. But to quote Emerson, "a foolish consistency is the hobgoblin of
small minds".

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[Keith Thompson]

Richard Heathfield <in*****@invalid.invalidwrites:
[...]

Touche'. But to quote Emerson, "a foolish consistency is the hobgoblin of
small minds".

Little minds, not small minds. (Like mine, apparently.)

--
Keith Thompson (The_Other_Keith) 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.

[Karthikeyan D]

sp****@gmail.com wrote:

I decided to do a little experiment with the programme below.

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;

}

int main() {

return 0 ;
}

The Sun compiler , lint on Solaris and gcc -Wall did not
produce any warnings.

On Solaris, running lint with the option -Nlevel=2 gives the following
message for the above program

return of a pointer to local variable
local defined at aaa.c(3) :: aaa.c(8)

Thanks

Karthik

[websnarf]

Richard Heathfield wrote:

BubbaGump said:

It's apparently not good for normal people.

C is fine for normal people who know how to think.

And who are willing to expend an unbounded amount of energy to keep
yourself from cutting your fingers off.

[...] If you don't know how to
think, stay away not just from C, but from programming.

But this is a response to your own generated statement, not his
original thesis.

BG is probably like most people, who have decided they just don't have
the energy to deal with juggling ignited razor blades just to deal with
trivial things like abstract data types. Or maybe he's just sick of
the fact that no matter how good you are you cannot sustain writing
perfect, or even near perfect code in C in single large projects
without similarly large (and often on-going) costs.

--
Paul Hsieh
http://www.pobox.com/~qed/
http://bstring.sf.net/

[Richard Heathfield]

we******@gmail.com said:

<polemic snipped>

Nothing left.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[goose]

BubbaGump wrote:
<snipped>

Definition of the day:

C is good for anal retentive people who catch most of their own
mistakes.

"left-handed compliment" :-)

goose,

[goose]

Keith Thompson wrote:

Richard Heathfield <in*****@invalid.invalidwrites:
[...]

Touche'. But to quote Emerson, "a foolish consistency is the hobgoblin of
small minds".

Little minds, not small minds. (Like mine, apparently.)

See? Its things like that which identifies
the C programmer in everyday conversation :-)
goose,

[spibou]

Karthikeyan D wrote:

sp****@gmail.com wrote:

I decided to do a little experiment with the programme below.

int *foo(void)
{
int local;
int *pointer;

pointer = &local;

return pointer;

}

int main() {

return 0 ;
}

The Sun compiler , lint on Solaris and gcc -Wall did not
produce any warnings.

On Solaris, running lint with the option -Nlevel=2 gives the following
message for the above program

return of a pointer to local variable
local defined at aaa.c(3) :: aaa.c(8)

I had never read the lint man page but I could have never
imagined that a warning tool does not as a default run with
the highest level of warnings. Utterly incomprehensible
design choice.

Thanks for opening my eyes. lint has now been aliased as
lint -Ncheck=%all -Nlevel=4

Spiros Bousbouras

[Keith Thompson]

"goose" <ru**@webmail.co.zawrites:

Keith Thompson wrote:

>Richard Heathfield <in*****@invalid.invalidwrites:
[...]

Touche'. But to quote Emerson, "a foolish consistency is the hobgoblin of
small minds".

Little minds, not small minds. (Like mine, apparently.)

See? Its things like that which identifies
the C programmer in everyday conversation :-)

Its --It's
identify --identifies

(Ok, ok, I'll stop now.)

--
Keith Thompson (The_Other_Keith) 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.

[Eric Sosman]

Keith Thompson wrote:

"goose" <ru**@webmail.co.zawrites:

>>Keith Thompson wrote:

>>>Richard Heathfield <in*****@invalid.invalidwrites:
[...]

Touche'. But to quote Emerson, "a foolish consistency is the hobgoblin of
small minds".

Little minds, not small minds. (Like mine, apparently.)

See? Its things like that which identifies
the C programmer in everyday conversation :-)

Its --It's
identify --identifies

(Ok, ok, I'll stop now.)

that -which ...

--
Eric Sosman
es*****@acm-dot-org.invalid

[Frederick Gotham]

Eric Sosman posted:

that -which ...

"that" in the place of "which" is quite acceptable, both in written and
spoken English.

Even when I'm intentionally trying to write fancy, I sometimes use "that"
instead of "which" in some places. I believe it has even more acceptance than
"who" in the place of "whom".

--

Frederick Gotham

[Eric Sosman]

Frederick Gotham wrote:

Eric Sosman posted:

>that -which ...

"that" in the place of "which" is quite acceptable, both in written and
spoken English.

Not to me, you-- you-- you Visigoth! (Note, too, the
curious inversion of notation used in the post to which I
responded. My correction, read in that notation, suggests
substituting "that" for "which," not "which" for "that.")

Even when I'm intentionally trying to write fancy, I sometimes use "that"
instead of "which" in some places. I believe it has even more acceptance than
"who" in the place of "whom".

It's been noted that people when speaking aloud tend to
use "which" and "that" correctly, but when writing tend to
get all formal and stuffified and use "which" because it seems
more dignified even when it's wrong.

http://stipo.larc.nasa.gov/sp7084/sp7084ch1.html#1.3.3.
http://www.bartleby.com/64/C001/062.html
http://www.worldwidewords.org/articles/which.htm
http://www.kentlaw.edu/academics/lrw...nd_Nonrest.htm

--
Eric Sosman
es*****@acm-dot-org.invalid

[J. J. Farrell]

Eric Sosman wrote:

Keith Thompson wrote:

"goose" <ru**@webmail.co.zawrites:

>
See? Its things like that which identifies
the C programmer in everyday conversation :-)

Its --It's
identify --identifies

(Ok, ok, I'll stop now.)

that -which ...

Which gives us "It's things like which which identify the C programmer
in everyday conversation". Some mistake, Shirley?

[Eric Sosman]

J. J. Farrell wrote:

Eric Sosman wrote:

>>Keith Thompson wrote:

>>>"goose" <ru**@webmail.co.zawrites:

See? Its things like that which identifies
the C programmer in everyday conversation :-)
Its --It's
identify --identifies

(Ok, ok, I'll stop now.)

that -which ...

Which gives us "It's things like which which identify the C programmer
in everyday conversation". Some mistake, Shirley?

Actually, no. Correctly written (I'm laying myself
WIDE open here) it's

It's things like that that identify the C
programmer in everyday blather.

(As I've mentioned in another post, the "-->" notation
seems backwards, or at least inconsistently applied. In the
"Its --It's" case it suggests replacing the incorrect "Its"
with the correct "It's," but in "identify --identifies" the
replacer/replacee roles are reversed. My "that --which"
followed the latter model, on the assumption that the direction
of the arrow had to do with whether the number of letters in
the correct word was even or odd. Remind me not to let Keith
design my next programming language, okay? ;-)

--
Eric Sosman
es*****@acm-dot-org.invalid

[Keith Thompson]

Eric Sosman <es*****@acm-dot-org.invalidwrites:
[...]

>>>Keith Thompson wrote:
"goose" <ru**@webmail.co.zawrites:

>See? Its things like that which identifies
>the C programmer in everyday conversation :-)
Its --It's
identify --identifies

[...]

(As I've mentioned in another post, the "-->" notation
seems backwards, or at least inconsistently applied. In the
"Its --It's" case it suggests replacing the incorrect "Its"
with the correct "It's," but in "identify --identifies" the
replacer/replacee roles are reversed. My "that --which"
followed the latter model, on the assumption that the direction
of the arrow had to do with whether the number of letters in
the correct word was even or odd. Remind me not to let Keith
design my next programming language, okay? ;-)

Yeah, that's it, it's about whether the number of letters is odd or
even. I couldn't have just screwed up.

--
Keith Thompson (The_Other_Keith) 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.

[Default User]

Eric Sosman wrote:

Frederick Gotham wrote:

"that" in the place of "which" is quite acceptable, both in written
and spoken English.

Not to me, you-- you-- you Visigoth! (Note, too, the
curious inversion of notation used in the post to which I
responded. My correction, read in that notation, suggests
substituting "that" for "which," not "which" for "that.")

Even when I'm intentionally trying to write fancy, I sometimes use
"that" instead of "which" in some places. I believe it has even
more acceptance than "who" in the place of "whom".

It's been noted that people when speaking aloud tend to
use "which" and "that" correctly, but when writing tend to
get all formal and stuffified and use "which" because it seems
more dignified even when it's wrong.

The general rule of thumb, "that" being for prescriptive cases and
"which" for non-prescriptive cases, is one of those things that's not
really a grammatical rule. In general, I find that to be a decent rule,
and use it myself, but I don't consider it wrong to do it otherwise.

Once again I feel like I'm on alt.usage.english.

Brian

[Mabden]

"Frederick Gotham" <fg*******@SPAM.comwrote in message
news:QF*******************@news.indigo.ie...

Eric Sosman posted:

that -which ...

"that" in the place of "which" is quite acceptable, both in written and
spoken English.

Even when I'm intentionally trying to write fancy, I sometimes use "that"
instead of "which" in some places. I believe it has even more acceptance

than

"who" in the place of "whom".

And he in place of him, sure that's gaining acceptance all over the place.
Just axe around.

Why is this hard?!
ex:
"Did you go with him to the mall?" "With whom did you go to the mall?"
object: him = whom
vesus
"He went to the mall." "Who went to the mall?"
subject: he = who

See how they add the M to the one that's the object? The subject is always
he/she/who.

Now that I think about it, this should probably be taken over to
Subject-Object-Oriented forum...

--
Mabden

[Mabden]

"goose" <ru**@webmail.co.zawrote in message
news:11**********************@b28g2000cwb.googlegr oups.com...

BubbaGump wrote:
<snipped>

Definition of the day:

C is good for anal retentive people who catch most of their own
mistakes.

"left-handed compliment" :-)

You don't need to debug, if you don't put the bugs in, in the first place...

--
Mabden

[Andrew Poelstra]

On 2006-07-29, Mabden <Ma****@SBCglobal.netwrote:

"goose" <ru**@webmail.co.zawrote in message
news:11**********************@b28g2000cwb.googlegr oups.com...

>BubbaGump wrote:
<snipped>

Definition of the day:

C is good for anal retentive people who catch most of their own
mistakes.

"left-handed compliment" :-)

You don't need to debug, if you don't put the bugs in, in the first place...

Of course! You've revolutionized programming. Thank you so much for
discovering how to save us countless hours of debugging. And here we
were deliberately putting bugs into our programs. Like monkeys.

--
Andrew Poelstra <website down>
To reach my email, use <email also down>
New server ETA: 42

[Frederick Gotham]

Mabden posted:

I believe it has even more acceptance than "who" in the place of
"whom".

See how they add the M to the one that's the object? The subject is always
he/she/who.

I'm aware of the usage of "whom" :)

I'll rephrase my original statement for clarity:

I believe it has even more acceptance than "who" in the place of "whom" (in
the accusative case, or dative case).

--

Frederick Gotham

[Joe Wright]

Andrew Poelstra wrote:

On 2006-07-29, Mabden <Ma****@SBCglobal.netwrote:

>"goose" <ru**@webmail.co.zawrote in message
news:11**********************@b28g2000cwb.googleg roups.com...

>>BubbaGump wrote:
<snipped>

Definition of the day:

C is good for anal retentive people who catch most of their own
mistakes.
"left-handed compliment" :-)

You don't need to debug, if you don't put the bugs in, in the first place...

Of course! You've revolutionized programming. Thank you so much for
discovering how to save us countless hours of debugging. And here we
were deliberately putting bugs into our programs. Like monkeys.

I suppose Mabden had his tongue in his cheek saying that. But he's not
really wrong. If you write good code, it's good. When I get into a bind
I usually put a printf() statement in the middle of the mess to tell me
what's happening. I've never used a C debugger.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[lawrence.jones]

Default User <de***********@yahoo.comwrote:

>
The general rule of thumb, "that" being for prescriptive cases and
"which" for non-prescriptive cases, is one of those things that's not
really a grammatical rule.

In fact, Fowler seems to have made it up himself in a futile attempt to
"fix" an ambiguity that English speakers have been quite comfortable
with since time immemorial.

-Larry Jones

It's hard to be religious when certain people are never
incinerated by bolts of lightning. -- Calvin

[Ian Collins]

Joe Wright wrote:

Andrew Poelstra wrote:

>On 2006-07-29, Mabden <Ma****@SBCglobal.netwrote:

>>"goose" <ru**@webmail.co.zawrote in message
news:11**********************@b28g2000cwb.google groups.com...

BubbaGump wrote:
<snipped>

Definition of the day:

C is good for anal retentive people who catch most of their own
mistakes.

"left-handed compliment" :-)

You don't need to debug, if you don't put the bugs in, in the first
place...

Of course! You've revolutionized programming. Thank you so much for
discovering how to save us countless hours of debugging. And here we
were deliberately putting bugs into our programs. Like monkeys.

I suppose Mabden had his tongue in his cheek saying that. But he's not
really wrong. If you write good code, it's good. When I get into a bind
I usually put a printf() statement in the middle of the mess to tell me
what's happening. I've never used a C debugger.

Or write your code test first, you shouldn't need a debugger if you do
this well. If you make a change and a test fails, just undo the change
and try another way.

--
Ian Collins.

[goose]

Ian Collins wrote:

<snipped>

If you make a change and a test fails, just undo the change
and try another way.

Unless your /test/ invokes UB :-)

"Hey the test worked, lets move on"

six months later ...

"The problem *has* to be in these 20 lines
I added yesterday. After all, the test was working
fine until these 20 lines were added."

goose,
Yes; that actually does happen :-)