will I get Memory leak..

[gNash]

Hi all,

void main()
{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");
fp[10]='\0';
free(fp);
}

Please refer the program for my questions..

1. Can any one tell me if would i assign '\0' at middle of
dynamically assigned memory area will i get memory leak.. ??
2 . Will "free()" delete all the memory which allocated by
dynamically even NULL values has been added in middle of that.??
3. How let i know that will i get memory leak in a program?? any
compiler option are there ?? Can i use splint tool ?

Thanks,
Ganesh

[Richard Bos]

gNash <ga**********@g mail.comwrote:

void main()

This is wrong. It should be

int main()

or by preference,

int main(void)

{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

This is wrong. You copy 27 characters (one whole alphabet, plus the
terminating null character) into space which can only hold 26 bytes.

fp[10]='\0';
free(fp);

These, however, are both absolutely fine, and should cause no problems
whatsoever, once you fix the bugs in the lines above them.

}

Richard

[Spiros Bousbouras]

On Nov 14, 12:31 pm, gNash <ganeshamu...@g mail.comwrote:

Hi all,

void main()
{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");
fp[10]='\0';
free(fp);
}

Please refer the program for my questions..

1. Can any one tell me if would i assign '\0' at middle of
dynamically assigned memory area will i get memory leak.. ??
2 . Will "free()" delete all the memory which allocated by
dynamically even NULL values has been added in middle of that.??
3. How let i know that will i get memory leak in a program?? any
compiler option are there ?? Can i use splint tool ?

Richard Bos has answered your main questions. I will simply
add that the character with value 0 is referred to as NUL not
NULL. For detecting memory leaks valgrind has a good reputation.

[gNash]

On Nov 14, 5:34 pm, [e-mail] (Richard Bos) wrote:

gNash <ganeshamu...@g mail.comwrote:

void main()

This is wrong. It should be

int main()

or by preference,

int main(void)

{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

This is wrong. You copy 27 characters (one whole alphabet, plus the
terminating null character) into space which can only hold 26 bytes.

fp[10]='\0';
free(fp);

These, however, are both absolutely fine, and should cause no problems
whatsoever, once you fix the bugs in the lines above them.

}

Richard

Hi Richard..

the int main(void) and malloc(26+1) it is not my doubt my doubts
are posted clearly.. Please reply for it.

Thankingyou,

[James Kuyper]

gNash wrote:

On Nov 14, 5:34 pm, [e-mail] (Richard Bos) wrote:

>gNash <ganeshamu...@g mail.comwrote:

>> void main()

This is wrong. It should be

int main()

or by preference,

int main(void)

>> {
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

This is wrong. You copy 27 characters (one whole alphabet, plus the
terminating null character) into space which can only hold 26 bytes.

>> fp[10]='\0';
free(fp);

These, however, are both absolutely fine, and should cause no problems
whatsoever, once you fix the bugs in the lines above them.

>> }

Richard

Hi Richard..

the int main(void) and malloc(26+1) it is not my doubt my doubts
are posted clearly.. Please reply for it.

He did. He justed added extra advice which you clearly need, since you
weren't following it.

[gNash]

On Nov 14, 5:50 pm, James Kuyper <jameskuy...@ve rizon.netwrote:

gNash wrote:

On Nov 14, 5:34 pm, [e-mail] (Richard Bos) wrote:

gNash <ganeshamu...@g mail.comwrote:
void main()
This is wrong. It should be

int main()

or by preference,

int main(void)

> {
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");
This is wrong. You copy 27 characters (one whole alphabet, plus the
terminating null character) into space which can only hold 26 bytes.

> fp[10]='\0';
free(fp);
These, however, are both absolutely fine, and should cause no problems
whatsoever, once you fix the bugs in the lines above them.

> }
Richard

Hi Richard..

the int main(void) and malloc(26+1) it is not my doubt my doubts
are posted clearly.. Please reply for it.

He did. He justed added extra advice which you clearly need, since you
weren't following it.

Thanks for advice.. but i have little confusion when i add '\0' and
free() will clear whole memory since '\0' representing end of array.
am i right?

[Ben Bacarisse]

gNash <ga**********@g mail.comwrites:

void main()
{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

You should get into the habit now or always checking the return from
malloc. Also, 26 is not enough for this string. You need space for
27 bytes.

fp[10]='\0';
free(fp);
}

Please refer the program for my questions..

1. Can any one tell me if would i assign '\0' at middle of
dynamically assigned memory area will i get memory leak.. ??

No.

2 . Will "free()" delete all the memory which allocated by
dynamically even NULL values has been added in middle of that.??

Yes. BTW, NULL is not the same as '\0'. That is a null byte.

3. How let i know that will i get memory leak in a program?? any
compiler option are there ?? Can i use splint tool ?

There is an excellent tool called "valgrind" that can do this (and
more) to help you find memory allocation errors. splint (and friends)
can tell you about possible portability issues and about errors that
can be detected without running your program.

--
Ben.

[gNash]

On Nov 14, 5:59 pm, Ben Bacarisse <ben.use...@bsb .me.ukwrote:

gNash <ganeshamu...@g mail.comwrites:

void main()
{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

You should get into the habit now or always checking the return from
malloc. Also, 26 is not enough for this string. You need space for
27 bytes.

fp[10]='\0';
free(fp);
}

Please refer the program for my questions..

1. Can any one tell me if would i assign '\0' at middle of
dynamically assigned memory area will i get memory leak.. ??

No.

2 . Will "free()" delete all the memory which allocated by
dynamically even NULL values has been added in middle of that.??

Yes. BTW, NULL is not the same as '\0'. That is a null byte.

3. How let i know that will i get memory leak in a program?? any
compiler option are there ?? Can i use splint tool ?

There is an excellent tool called "valgrind" that can do this (and
more) to help you find memory allocation errors. splint (and friends)
can tell you about possible portability issues and about errors that
can be detected without running your program.

--
Ben.

Thank you all.. i am clear..

Thank you again..
Ganesh.

[gNash]

On Nov 14, 5:59 pm, Ben Bacarisse <ben.use...@bsb .me.ukwrote:

gNash <ganeshamu...@g mail.comwrites:

void main()
{
char *fp;
fp=malloc(26);
strcpy(fp,"ABCD EFGHIJKLMNOPQRS TUVWXYZ");

You should get into the habit now or always checking the return from
malloc. Also, 26 is not enough for this string. You need space for
27 bytes.

fp[10]='\0';
free(fp);
}

Please refer the program for my questions..

1. Can any one tell me if would i assign '\0' at middle of
dynamically assigned memory area will i get memory leak.. ??

No.

2 . Will "free()" delete all the memory which allocated by
dynamically even NULL values has been added in middle of that.??

Yes. BTW, NULL is not the same as '\0'. That is a null byte.

3. How let i know that will i get memory leak in a program?? any
compiler option are there ?? Can i use splint tool ?

There is an excellent tool called "valgrind" that can do this (and
more) to help you find memory allocation errors. splint (and friends)
can tell you about possible portability issues and about errors that
can be detected without running your program.

--
Ben.

Could you any one please tell me how is free() is working?

[James Kuyper]

gNash wrote:
....

Thanks for advice.. but i have little confusion when i add '\0' and
free() will clear whole memory since '\0' representing end of array.
am i right?

No. You are confusing three different things: strings, arrays, and
dynamic memory allocation.
Many C library functions read or write null-terminated strings. The
free() function is NOT one of them.

Arrays have a length that can be determined at the point of declaration.
Writing a null character to an array does not change its size, it merely
affects how much of that array will be read by routines that take
strings as input.

Dynamic memory allocations have a size that is determined solely by the
call to malloc(), calloc(), or realloc() that allocated the memory. The
size is not changed by what you write into that memory, not even if what
you write is a null character. The free() function deallocates the
entire amount of memory allocated.