finding max value of size_t

[subramanian100in]

Consider the following program

#include <limits.h>
#include <stddef.h>

int main(void)
{
size_t size;
size_t bytes = sizeof(size_t);

if (bytes == sizeof(unsigned int))
size = UINT_MAX;
else if (bytes == sizeof(unsigned long))
size = ULONG_MAX;
else if (bytes == sizeof(unsigned long long))
size = ULLONG_MAX;

return 0;
}

Can this code give the maximum value of size_t in all standard C
compliant compilers.

[Richard Heathfield]

su************* *@yahoo.com, India said:

Consider the following program

#include <limits.h>
#include <stddef.h>

int main(void)
{
size_t size;
size_t bytes = sizeof(size_t);

if (bytes == sizeof(unsigned int))
size = UINT_MAX;
else if (bytes == sizeof(unsigned long))
size = ULONG_MAX;
else if (bytes == sizeof(unsigned long long))
size = ULLONG_MAX;

return 0;
}

Can this code give the maximum value of size_t in all standard C
compliant compilers.

No, because there is no guarantee that size_t has the same size as any
other integer type. But you can do this:

#include <stddef.h>

int main(void)
{
size_t size = (size_t)-1;
return 0;
}

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

[subramanian100in]

(size_t) - 1

Please let me know whether this will give the maximum value of size_t

[Richard Heathfield]

su************* *@yahoo.com, India said:

(size_t) - 1

Please let me know whether this will give the maximum value of size_t

Didn't I just do that? Yes, it will.

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

[subramanian100in]

Yes. It does give the expected value. Thanks.

The following is a beginner's question.

What is (size_t) ? ie what is parenthesized size_t ? how does it
produce a value ?

Please explain

[Chris Dollin]

su************* *@yahoo.com, India wrote:

Yes. It does give the expected value. Thanks.

The following is a beginner's question.

What is (size_t) ? ie what is parenthesized size_t ?

Your C book should tell you. (If you haven't got one, get
one; you'll make progress faster than by being drip-fed via
netnews. See the FAQ for suggestions.)

It's a type-name in brackets.

In the expression `(size_t) -1`, it's a /cast/, requesting
a conversion of the expression `-1` to the type `size_t`.

[Note that `-1` is an expression, not a literal, consisting
of the unary minus operator applied to the literal `1`.
It happens to be a /constant expression/, meaning that the
compiler can -- and in some circumstances [1], must -- evaluate
it at compile-time.]

how does it produce a value ?

It converts the value -1 to the guaranteed-unsigned type
`size_t` by adding/subtracting one more than the maximum
value of that type: ie taking it modulo maxvalue+1.

[1] eg as a case label.

--
Chris "electric hedgehog" Dollin
Nit-picking is best done among friends.

[shadowman]

su************* *@yahoo.com, India wrote:

Yes. It does give the expected value. Thanks.

The following is a beginner's question.

What is (size_t) ? ie what is parenthesized size_t ? how does it
produce a value ?

Please explain

It's a typecast. In this case it's converting the value -1 to the type
size_t -- which is unsigned.

[Richard Heathfield]

shadowman said:

su************* *@yahoo.com, India wrote:

>Yes. It does give the expected value. Thanks.

The following is a beginner's question.

What is (size_t) ? ie what is parenthesized size_t ? how does it
produce a value ?

Please explain

It's a typecast.

Well, close. It's a cast. C doesn't have anything called "typecast".

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

[shadowman]

Richard Heathfield wrote:

shadowman said:

>su************* *@yahoo.com, India wrote:

>>Yes. It does give the expected value. Thanks.

The following is a beginner's question.

What is (size_t) ? ie what is parenthesized size_t ? how does it
produce a value ?

Please explain

It's a typecast.

Well, close. It's a cast. C doesn't have anything called "typecast".

I must have been thinking about actors who always play similar roles.

[santosh]

su************* *@yahoo.com, India wrote:

(size_t) - 1

Please let me know whether this will give the maximum value of size_t

Please quote context.

Yes it will, not only for size_t, but for any unsigned type, (with the
appropriate cast).

You can also use the SIZE_MAX macro defined in stdint.h, to get the
maximum value of the system's size_t type. It's however a C99 feature.