[Bug c++/32786] New: Incorrect code compiles and runs well

[Bug c++/32786] New: Incorrect code compiles and runs well

[bachmann dot matt at gmail dot com]

This is my first bug report... I am not quite sure what you mean by
host/target/build triplet so ill give you what I can

complied on an 686 architecture in linux. 

#include<iostream>
#include<cstdlib>
using namespace std;

/**
 * Matt Bachmann
 * CS 331
 * HW1 Due: July 9th 2007
 * Main method shows different ways of traversing strings
 */ 
int main() {
        char mary[25] = "Mary had a little lamb.";
        char* moby = "Thar she blows!";

        cout << strlen(mary) << endl << endl;
        for(unsigned int i = 0; i < strlen(mary); i++) {
                for(unsigned int a = i; a < strlen(mary); a++) {
                        cout << mary[a];
                }
                cout << endl;
        }
        cout << endl;
        cout << strlen(moby) << endl << endl;
        while(moby != '\0') { 
                cout << moby << endl;
                moby++;
        }
        system("PAUSE");
        return EXIT_SUCCESS;
}

the condition in the while loop should cause an infinite loop and should be
moby*


-- 
           Summary: Incorrect code compiles and runs well
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bachmann dot matt at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32786

[Bug c++/32786] Incorrect code compiles and runs well

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-07-17 03:17 -------
> the condition in the while loop should cause an infinite loop and should be
> moby*
I think you mean *moby.  Anyways it is just undefined that you go past the
array bounds when incrementing a pointer so we know it will not be an infinite
loop and has a finite length.

Anyways the program crashes for me which is a valid behavior.

        while(moby != '\0') { 

This is valid as '\0' can be considered the NULL pointer.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32786

[Bug c++/32786] Incorrect code compiles and runs well

[bachmann dot matt at gmail dot com]

------- Comment #2 from bachmann dot matt at gmail dot com  2007-07-17 03:39 -------
but thats just it! alright it does not infinite loop but for me it does not
crash, it runs perfectly. Here is my output:

$ g++ HW1.cpp
$ ./a.out
23

Mary had a little lamb.
ary had a little lamb.
ry had a little lamb.
y had a little lamb.
had a little lamb.
had a little lamb.
ad a little lamb.
d a little lamb.
a little lamb.
a little lamb.
little lamb.
little lamb.
ittle lamb.
ttle lamb.
tle lamb.
le lamb.
e lamb.
lamb.
lamb.
amb.
mb.
b.
.

15

Thar she blows!
har she blows!
ar she blows!
r she blows!
she blows!
she blows!
he blows!
e blows!
blows!
blows!
lows!
ows!
ws!
s!
!

Is there any reason that anyone can think of why this would be? I showed my
professor and he is the one who suggested I submit a bug. It does this under
linux, but in windows using devC++(using a windows port of g++) it breaks as
its supposed to.


-- 

bachmann dot matt at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32786

[Bug c++/32786] Incorrect code compiles and runs well

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2007-07-17 03:58 -------
No, it is crashing.  Anyways this is just undefined behavior so any behavior
here is ok :).


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32786

[Bug c++/32786] Incorrect code compiles and runs well

[bachmann dot matt at gmail dot com]

------- Comment #4 from bachmann dot matt at gmail dot com  2007-07-17 04:04 -------
alright then. ::shrugs::

thanks


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32786