https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91434
Bug ID: 91434
Summary: gcc optimization behaviour is inconsistent with -O2
with 4.1.2 and 4.9.4
Product: gcc
Version: 4.9.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rajawrite at gmail dot com
Target Milestone: ---
Created attachment 46706
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46706&action=edit
member variable is not set to NULL when destructor is called manually once and
self destruction
In our project, we moved from g++ 4.1.2 to 4.9.4.
There is behaviour change with member variable setting to NULL when manually
called destructor and during self destruction.
ouput with gcc 4.9.4:
=====================
cds-build15:1044> /usr/local/bin/g++ -O2 sample1.cpp -o sample1.o
cds-build15:1045> ./sample1.o
FSPGI ctor1
FSPI ctor
FSPG ctor
FSPGI ctor
FSPGI dtor
m_g is not NULL
FSPG dtor
FSPI dtor
FSPGI dtor
m_g is not NULL
FSPG dtor
*** Error in `./sample1.o': double free or corruption (fasttop):
0x000000000137c010 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x81499)[0x7fd25345e499]
ouput with gcc 4.9.4 with -fno-tree-dse:
========================================
cds-build15:1048> /usr/local/bin/g++ -O2 -fno-tree-dse sample1.cpp -o sample1.o
cds-build15:1049> ./sample1.o
FSPGI ctor1
FSPI ctor
FSPG ctor
FSPGI ctor
FSPGI dtor
m_g is not NULL
FSPG dtor
FSPI dtor
FSPGI dtor
cds-build15:1050>
output with g++ 4.1.2:
======================
cds-build3:1011> g++ -O2 sample1.cpp -o sample1.o
cds-build3:1012> ./sample1.o
FSPGI ctor1
FSPI ctor
FSPG ctor
FSPGI ctor
FSPGI dtor
m_g is not NULL
FSPG dtor
FSPI dtor
FSPGI dtor
cds-build3:1013>
Please check if this is the correct behviour and -fno-tree-dse should be used
for this code and impact of disabling dse.
