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c++/7707: GCC 3.1.1 Optimization incomplete/incorrect : leaks temporary object
- From: plaflamme at konova dot com
- To: gcc-gnats at gcc dot gnu dot org
- Cc: lletourneau at konova dot com
- Date: 23 Aug 2002 23:01:36 -0000
- Subject: c++/7707: GCC 3.1.1 Optimization incomplete/incorrect : leaks temporary object
- Reply-to: plaflamme at konova dot com
>Number: 7707
>Category: c++
>Synopsis: GCC 3.1.1 Optimization incomplete/incorrect : leaks temporary object
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Fri Aug 23 16:06:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Konova Solutions Inc.
>Release: GCC 3.1.1
>Organization:
>Environment:
RedHat Linux 7.3
Dual Intel Pentium III 833 MHz
GCC compiled with:
--prefix=/usr/gcc-3.1.1 --enable-threads=posix --enable-languages=c,c++
>Description:
g++ seems not to optimize temporary objects copy correctly and results in a memory leak. The cpp file attached provides a example of how g++ fails to destruct a temporary object.
The output of the example shows that 2 temporary objects are created (using copy ctor) while only one of them is destructed.
A temporary object is created on the stack in method
operator+(const foo&, const foo&). The result of the operator+ is passed to another method taking a const foo as parameter. Doing so, g++ calls the copy constructor.
It is up to the compiler to actually call the copy ctor or not. g++ does not seem to optimize this copy, but then fails to destroy the object.
The attachment contains the cpp and ii files.
>How-To-Repeat:
>Fix:
Modifing the leakAFoo method to take a const foo& instead.
g++ is still to blame. Either the optimization is incomplete, or some logic is erronous when destroying temporary objects.
>Release-Note:
>Audit-Trail:
>Unformatted: