On September 22, 2008 14:42, in comp.lang.c,
do************* *@ymail.com
(do************ **@ymail.com) wrote:
Hello, I'm a highly experienced expert C programmer
Apparently, you are
a) egotistical, and
b) wrong
and I've written
this code to reverse a string in place.
I am /so/ sorry, both for you and your employer.
I think you could all learn
something from it!
I'm sure that you are right. After all, /I/ learned that you are much less
than the C programmer that you claim to be.
int reverse(char* reverseme){
int retval=-1;
if(retval!=NULL )
Useless test, as retval was initialized (and never altered) to a value
that will not equate to NULL
{
int len=strlen(retv al)
First real failure. retval is an integer, and the argument to
strlen() is a pointer-to-char. You can't get a valid result from
taking the "string length" of an integer.
Second failure: you did not #include the header that declares the
strlen() function. Thus, your compiler did not flag the above
assignment as an error (argument of incompatable type)
{
if(len>0)
So, what is the "string length" of an integer? And when would it be
greater than zero?
{
int half=len>>1;
Style hack: To be clearer to the intent of what sort of number
half represents, you should have coded this as
int half = len / 2;
Of course, since len is a nonsense value, half will also be a
nonsense value.
for(;retval<hal f;retval++){
reverseme[retval]^=reverseme[len-(retval+1)];
Undefined behaviour on first iteration, when retval == -1
reverseme[-1] is out of bounds.
reverseme[len-(retval+1)]=reverseme[retval];
Undefined behaviour on first iteration - same reason
reverseme[retval]^=reverseme[len-(retval+1)];
Undefined behaviour on first iteration - same reason
Plus, you've screwed up the "xor trick", and wiped out /both/
ends of the string with invalid values.
The head end now contains an array of 0x00 (up to
the ill-computed "midpoint") , while the tail end contains the
results of the head end xor the tail end.
}
}
}
return retval;
Of what use is this return value?
}
-Phil/CERisE
--
Lew Pitcher
Master Codewright & JOAT-in-training | Registered Linux User #112576
http://pitcher.digitalfreehold.ca/ | GPG public key available by request
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