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Subject: [Bug c++/55340] New: Invalid maybe unitialized warning
Date: Thu, 15 Nov 2012 12:51:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D55340

             Bug #: 55340
           Summary: Invalid maybe unitialized warning
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jwillemsen@remedy.nl


Created attachment 28698
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=3D28698
gzip with both preprocessed files

We have in some of our tests a warning that a variable may be used unitiali=
zed,
but we have validated that this is not the case (as far as we could tell).=
=20

We tried to reduce our code to a minimum, but the strange thing is that whe=
n we
remove some not related code, the warning is gone.=20

Attached 2 preprocessed files, t.cpp t2.cpp, compile using:
g++ --std=3Dc++0x -fno-strict-aliasing -fvisibility=3Dhidden
-fvisibility-inlines-hidden -O3 -ggdb -m64 -pthread -Wall -W -Wpointer-arith
-pipe -D_GNU_SOURCE    -c t.cpp

When compiling t.cpp we get:
In file included from testC.cpp:26:0:=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20
testC.h: In member function =E2=80=98void Test::union_union::swap(Test::uni=
on_union&)=E2=80=99:=20
testC.h:764:3: warning: =E2=80=98*((void*)(& intermediate)+8).Test::unionTy=
pe::disc_=E2=80=99
may be used uninitialized in this function [-Wmaybe-uninitialized]=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20
testC.h:1325:27: note: =E2=80=98*((void*)(& intermediate)+8).Test::unionTyp=
e::disc_=E2=80=99
was declared here=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
When compiling t2.cpp there is no warning. If you check the diff between t.=
cpp
and t2.cpp you will see that the code that triggers the warning is still th=
ere.

We have reduced the code to the point that removal of any type would not
trigger the warning.