c-c++ memory corruption and memory leaks.mht

linux下c++编程的好文章

            <TD><PRE>struct ABC abc;
struct ABC *abc_ptr =3D &amp;abc;
...
free(abc_ptr);
</PRE></TD></TR></TBODY></TABLE></DD></DL>
      <P>
      <HR>

      <P><B>Incorrect use of delete: The delete must match the use of =
new.</B>=20
      <P>The pairing is new/delete and new [] / delete[]=20
      <DL>
        <DD>
        <TABLE cellSpacing=3D1 cellPadding=3D4 width=3D"100%" =
bgColor=3D#000000=20
border=3D1>
          <TBODY>
          <TR bgColor=3D#c0c0c0>
            <TD><PRE>ClassABC *abc_ptr =3D new ClassABC[100];
...
delete [] abc_ptr;
</PRE></TD></TR></TBODY></TABLE></DD></DL>Use of "delete abc_ptr" is an=20
      error.=20
      <P>Do not use malloc()/free() with a C++ class as it will not call =
the=20
      constructor or destructor. Also malloc()/free() can not be mixed =
with=20
      new/delete. i.e. Free() can not be used to free memory allocated =
with new=20
      and delete can not be used to free memory allocated with malloc(). =

      <P>
      <HR>

      <P><B>Exception Errors:</B>=20
      <P>Freeing memory never allocated. If you use a constructor to =
allocate=20
      memory but an exception is thrown before all is allocated, the =
destructor=20
      needs to be aware that fact or else it may try to free memory =
which was=20
      never allocated.=20
      <P>Also the converse is true. If the destructor throws an =
exception,=20
      subsequent steps which free memory may not be executed. This =
applies to=20
      the destructor and all nested destructors which handle/re-throw =
the=20
      exception while the stack unwinds.=20
      <P>
      <HR>

      <P><B>Pointer persistence:</B>=20
      <P>Function returning a pointer from the stack which can get =
overwritten=20
      by the calling function (in this case main()):=20
      <DL>
        <DD>
        <TABLE cellSpacing=3D1 cellPadding=3D4 width=3D"100%" =
bgColor=3D#000000=20
border=3D1>
          <TBODY>
          <TR bgColor=3D#c0c0c0>
            <TD><PRE>int *get_ii()
{
   int ii;        // Local stack variable
   ii =3D 2;
   return &amp;ii;
}
main()
{
  int *ii;
  ii =3D get_ii();  // After this call the stack is given up by the =
routine=20
                  // get_ii() and its values are no longer safe.

  ... Do stuff
  ..  ii may be corrupt by this point.
}
</PRE></TD></TR></TBODY></TABLE></DD></DL>This is also true for a local=20
      variable within the scope of only { and } as well as for the scope =
of a=20
      function.=20
      <P>
      <HR>

      <P><B>Incorrect passing of a function argument:</B>=20
      <P>If the pointer is passed around as an argument and does not get =
passed=20
      correctly, one may try to free the incorrect pointer.=20
      <P>
      <HR>

      <P><B>Mixing the object base class and derived class:</B>=20
      <P>If mixing the object base class and derived class when passing =
an=20
      object by value as a function parameter, make sure that you =
understand=20
      what may be lost.=20
      <DL>
        <DD>
        <TABLE cellSpacing=3D1 cellPadding=3D4 width=3D"100%" =
bgColor=3D#000000=20
border=3D1>
          <TBODY>
          <TR bgColor=3D#c0c0c0>
            <TD><PRE>function_A(BaseClass baseClass_ptr)
{
...
}

// Call to function
function_A(derivedClass_ptr); // Note that much of the information =
contained=20
                            // in the derived class will not be passed =
into
                            // the function including virtual =
destructors.
</PRE></TD></TR></TBODY></TABLE></DD></DL>
      <P>
      <HR>

      <P><B>Copying an object:</B>=20
      <P>Don't use memcpy() or any bit for bit copy function to copy an =
object.=20
      It will not execute the class constructor. What kind of person =
would do=20
      this?? Passing an object in a va_arg() list will result in a bit =
for bit=20
      copy and will not use the default copy constructor.=20
      <P><A name=3DLINKS></A>
      <HR>

      <TABLE cellSpacing=3D0 cellPadding=3D2 width=3D"100%" border=3D0>
        <TBODY>
        <TR bgColor=3D#ffcc33>
          <TD><B><BIG>Links:</BIG></B></TD></TR></TBODY></TABLE>
      <P>
      <UL>
        <LI><A=20
        =
href=3D"http://www.informit.com/articles/article.asp?p=3D30642&amp;seqNum=
=3D9">C++=20
        Memory and Resource Management: Improper Use of auto_ptr</A>=20
        <LI><A=20
        =
href=3D"http://www.eventhelix.com/RealtimeMantra/Basics/debugging_softwar=
e_crashes_2.htm">Debugging=20
        Software Crashes</A>=20
        <LI><A=20
        =
href=3D"http://users.actcom.co.il/~choo/lupg/tutorials/unix-memory/unix-m=
emory.html">Unix=20
        And C/C++ Runtime Memory Management For Programmers</A>=20
        <LI><A=20
        =
href=3D"http://www.linuxdevcenter.com/pub/a/linux/2003/05/08/cpp_mm-1.htm=
l?page=3D1">C++=20
        Memory Management: From Fear to Triumph</A> </LI></UL>
      <P>Related YoLinux Tutorials:=20
      <UL>
        <LI><A=20
        =
href=3D"http://www.yolinux.com/TUTORIALS/LinuxTutorialSoftwareDevelopment=
.html#MEMORYTOOLS">Software=20
        Development Tools: Memory Debugging Development Tools</A>=20
        <LI><A =
href=3D"http://www.yolinux.com/TUTORIALS/LinuxTutorialC++.html">C++=20
        programming on Linux</A>=20
        <LI><A=20
        =
href=3D"http://www.yolinux.com/TUTORIALS/LinuxTutorialC++CodingStyle.html=
">C++=20
        Coding styles and practices </A>
        <LI><A=20
        =
href=3D"http://www.yolinux.com/TUTORIALS/LinuxTutorialC++Structures.html"=
>C++=20
        structures</A>=20
        <LI><A=20
        =
href=3D"http://www.yolinux.com/TUTORIALS/index.html#PROGRAMMING">Programm=
ing=20
        Tutorials</A> </LI></UL>
      <P><A name=3DBOOKS></A>
      <HR SIZE=3D5>

      <TABLE cellSpacing=3D0 cellPadding=3D2 width=3D"100%" border=3D0>
        <TBODY>
        <TR bgColor=3D#ffcc33>
          <TD vAlign=3Dtop><IMG=20
            =
src=3D"http://www.yolinux.com/TUTORIALS/images/book40.gif"><B><BIG>Books:=
</BIG></B></TD></TR></TBODY></TABLE>
      <P>
      <DL>
        <DD>
        <TABLE cellPadding=3D5 width=3D"100%" border=3D1>
          <TBODY>
          <TR>
            <TD><IMG=20
              =
src=3D"http://www.yolinux.com/BOOKS/0321125185.01.MZZZZZZZ.jpg"></TD>
            <TD vAlign=3Dtop>C++ Gotchas: Avoiding Common Problems in =
Coding and=20
              Design <BR>by Stephen C. Dewhurst <BR>ISBN #0321125185,=20
              Addison-Wesley Professional=20
              <P></P>
            <TD vAlign=3Dtop><A=20
              =
href=3D"http://www.amazon.com/exec/obidos/ASIN/0321125185/yolinux-20"><IM=
G=20
              alt=3DAmazon.com=20
              =
src=3D"http://www.yolinux.com/TUTORIALS/images/Amazon-BuyABook88x31.gif">=
</A>=20
              <BR><IMG height=3D1=20
              =
src=3D"http://service.bfast.com/bfast/serve?bfmid=3D2181&amp;sourceid=3D3=
9358384&amp;bfpid=3D0321125185&amp;bfmtype=3Dbook"=20
              width=3D1 border=3D0 NOSAVE><A=20
              =
href=3D"http://service.bfast.com/bfast/click?bfmid=3D2181&amp;sourceid=3D=
39358384&amp;bfpid=3D0321125185&amp;bfmtype=3Dbook"=20
              target=3D_top><IMG height=3D60=20
              =
src=3D"http://www.yolinux.com/TUTORIALS/images/BarnesNobles.gif"=20
              width=3D75></A> </TD></TR>
          <TR>
            <TD><IMG=20
              =
src=3D"http://www.yolinux.com/BOOKS/0201924889.01.MZZZZZZZ.jpg"></TD>
            <TD vAlign=3Dtop>Effective C++: 50 Specific Ways to Improve =
Your=20
              Programs and Design (2nd Edition) <BR>by Scott Meyers =
<BR>ISBN=20
              #0201924889, Addison-Wesley Professional=20
              <P></P>
            <TD vAlign=3Dtop><A=20
              =
href=3D"http://www.amazon.com/exec/obidos/ASIN/0201924889/yolinux-20"><IM=
G=20
              alt=3DAmazon.com=20
              =
src=3D"http://www.yolinux.com/TUTORIALS/images/Amazon-BuyABook88x31.gif">=
</A>=20
              <BR><IMG height=3D1=20
              =
src=3D"http://service.bfast.com/bfast/serve?bfmid=3D2181&amp;sourceid=3D3=
9358384&amp;bfpid=3D0201924889&amp;bfmtype=3Dbook"=20
              width=3D1 border=3D0 NOSAVE><A=20
              =
href=3D"http://service.bfast.com/bfast/click?bfmid=3D2181&amp;sourceid=3D=
39358384&amp;bfpid=3D0201924889&amp;bfmtype=3Dbook"=20
              target=3D_top><IMG height=3D60=20
              =
src=3D"http://www.yolinux.com/TUTORIALS/images/BarnesNobles.gif"=20
              width=3D75></A> </TD></TR>
          <TR>
            <TD><IMG=20
              =
src=3D"http://www.yolinux.com/BOOKS/020163371X.01.MZZZZZZZ.jpg"></TD>
            <TD vAlign=3Dtop>More Effective C++: 35 New Ways to improve =
your=20
              Programs and Designs <BR>by Scott Meyers <BR>ISBN =
#020163371X,=20
              Addison-Wesley Professional=20
              <P></P>