Is it safe to return "char*" from functions?

[John Eskie]

Hello,

I've seen in some programs that they provide functions which has the
following prototype:
char *func1();

However I'm not sure it's safe. If the char array beeing returned is a local
variable such as:

char *func1()
{
char string[] = "Hello World";
return string;
}

then you got a problem because the string will be stored on stack which will
be de-allocated upon function return. So in reality the string is located on
a memory position which is availble for anyones use.
If keywords such as static or global data is returned the situation might be
different.
If you use new/malloc on the data you want to return it's safe but then
again you're making a memory leak unless the caller knows it's nessecary to
clean up.

Could anyone clear this up for me.

Thanks in advance.

-- John

 

[Spikinsson]

"John Eskie"

...

then you got a problem because the string will be stored on stack which will
be de-allocated upon function return. So in reality the string is located on
a memory position which is availble for anyones use.
yes

If keywords such as static or global data is returned the situation might be
different.
uhu

If you use new/malloc on the data you want to return it's safe but then
again you're making a memory leak unless the caller knows it's nessecary to
clean up.

indeed

 

[Peter van Merkerk]

Hello,

I've seen in some programs that they provide functions which has the
following prototype:
char *func1();

However I'm not sure it's safe. If the char array beeing returned is a local
variable such as:

char *func1()
{
char string[] = "Hello World";
return string;
}

then you got a problem because the string will be stored on stack which will
be de-allocated upon function return. So in reality the string is located on
a memory position which is availble for anyones use.
If keywords such as static or global data is returned the situation might be
different.
If you use new/malloc on the data you want to return it's safe but then
again you're making a memory leak unless the caller knows it's nessecary to
clean up.

Could anyone clear this up for me.

It seems you understand the issues with returning pointers very well. The
C++ solution for this particular example is to return std::string instead of
a char pointer, and your resource management problems are solved.