Re: memory leak in the code?
On 6 Jan., 19:45, Grizlyk <grizl...@yandex.ru> wrote:
kwikius wrote:
int * a = 0;
int * b = 0;
try {
a = new int [N];
...
delete a;
Excellent :). As i know, for each program we get at least one (hard to
detect and with random runtime apperance) error due to improper delete/
delete[] usage.
Not in idiomatic C++ where you "never" use operator delete [].
For example, the stupid program (http://grizlyk1.narod.ru/cpp_new/gcc/util=
s
) for adding source lines into gcc asm output has 3 levels of patching
of detected errors. Take a look at the last patch, file "to_do.txt":
It is quite stupid from a C++ viewpoint as it looks more like C. In
this case, You should expect using C, not C++ style.
1. possible memory leakage.
void Terr::do_copy(const char *const who)
{
if(who)try
{
const uint len=strlen(who);
if(!len)return;
char *const tmp=new char[len+1];
strcpy(tmp,who);
msg_copied=tmp;
}
catch(...){ msg_shared="no memory"; }
}
"strcpy(tmp,who)" can throw while "tmp" has no owner
This is not possible so far as I know. strcpy is C and thus does not
throw. Did you write your own strcpy?
patch:
char *const tmp=new char[len+1];
try{ strcpy(tmp,who); }catch(...){ delete[] tmp; throw; }
msg_copied=tmp;
2. Wrong delete for arrray
~Terr::Terr(){ delete msg_copied; }
patch:
~Terr::Terr(){ delete[] msg_copied; }
3. Wrong delete for arrray
Terr& operator= (const Terr& obj)
{
if( &obj != this )
{
msg_shared=obj.msg_shared;
delete msg_copied; msg_copied=0;
do_copy(obj.msg_copied);
}
return *this;
}
patch:
if(msg_copied){delete[] msg_copied; msg_copied=0;}
I agree, that the errors appeared due to my negligent work, this is
very bad habbit for programming, but there are many other people with
the same behaviour in the world. This is constant fact of nature :).
Well... you can't fight bad programming in any language.
And in addition, any desing work, being continuous iterational
process, inspires a little the negligence in work ( :) I have found
the couse ).
So, the only way to prevent the errors is explicit memory
declarations:
char * ptr; //C-style pointer
auto char * ptr; //can not delete/delete[]
heap char * ptr; //can delete heap/delete
heap[] char * msg_copied; //can delete heap[]/delete[]
other_memory_type char *ptr; //can delete other_memory_type
Maybe it will be added to C++.
Why? We already have std::vector (and std::string). Using either of
these would have avoided your problems.
/Peter