[Bug c++/40146] New: Unexplained "'<anonymous>' is used uninitialized in this function" warning

[Bug c++/40146] New: Unexplained "'<anonymous>' is used uninitialized in this function" warning

[caolanm at redhat dot com]

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With some code (attached) using an anonymous namespace I get an unexplained
"‘<anonymous>’ is used uninitialized in this function" with -Wall, with no
indication of what is seen to be used uninitialized. Changing the namespace to
a named one removes the error, as does removing part of the body of a used
method. 

g++ (GCC) 4.4.0 20090506 (Red Hat 4.4.0-4)

-DTEST1 names the namespace
-DTEST2 comments out the body of the offending method
"wiggling" the code makes it disappear/reappear, but difficult to know what the
problem is so as to make the test-case a more reasonable size

$ g++ -O2 -c -Wall foo.cxx
foo.cxx: In function ‘bool demo()’:
foo.cxx:4033: warning: ‘<anonymous>’ is used uninitialized in this function
foo.cxx:4033: note: ‘<anonymous>’ was declared here
$ g++ -DTEST1 -O2 -c -Wall foo.cxx
$ g++ -DTEST2 -O2 -c -Wall foo.cxx

Looks similar to bug #38908 but that one compiles without warnings here


-- 
           Summary: Unexplained "'<anonymous>' is used uninitialized in this
                    function" warning
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: caolanm at redhat dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[caolanm at redhat dot com]

------- Comment #1 from caolanm at redhat dot com  2009-05-14 13:09 -------
Created an attachment (id=17864)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17864&action=view)
test-case


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2009-05-14 14:31 -------
Well with -DTEST1, the functions which were in the anonymous namespace are now
in the normal namespace which means they are going to be exported from the TU
which changes the inlining decisions.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[bangerth at gmail dot com]

------- Comment #3 from bangerth at gmail dot com  2009-08-25 13:54 -------
Hm, can you try to come up with a smaller testcase for which it may be a bit
simpler to see what is going on?

Thanks
 W.


-- 

bangerth at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at gmail dot com
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[caolanm at redhat dot com]

------- Comment #4 from caolanm at redhat dot com  2009-08-27 11:17 -------
Created an attachment (id=18436)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18436&action=view)
smaller test-case

Here's a smaller one, perturbing nearly any line in this makes the warning go
away, various sample lines are commented as such in this 100 line example.

Like before...
g++ -DTEST -O2 -c -Wall foo.cxx
no warnings, while
g++ -O2 -c -Wall foo.cxx
foo.cxx: In function 'bool demo()':
foo.cxx:83: warning: '<anonymous>' is used uninitialized in this function
foo.cxx:83: note: '<anonymous>' was declared here


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[caolanm at redhat dot com]

-- 

caolanm at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |UNCONFIRMED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[bangerth at gmail dot com]

------- Comment #5 from bangerth at gmail dot com  2009-08-27 11:35 -------
The warning isn't triggered any more with current mainline. 

Can someone gives this a try with the current 4.4.x branch?

W.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[shawn dot starr at rogers dot com]

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------- Comment #6 from shawn dot starr at rogers dot com  2009-09-10 17:44 -------
I can reproduce this compiling Second Life from trunk

cc1plus: warnings being treated as errors                                       
/home/spstarr/Downloads/viewer-trunk/indra/llcommon/lldarray.h: In destructor
‘LLFrameStats::~LLFrameStats()’:                                         
/home/spstarr/Downloads/viewer-trunk/indra/llcommon/lldarray.h:60: error:
‘<anonymous>’ is used uninitialized in this function                         
/home/spstarr/Downloads/viewer-trunk/indra/llcommon/lldarray.h:60: note:
‘<anonymous>’ was declared here                                               
make[2]: *** [newview/CMakeFiles/secondlife-bin.dir/llframestats.o] Error 1     

In this case, the type being passed in is a class.


Given: Where FrameData is a private class inside LLFramestats

LLDynamicArray<FrameData> mFrameData;


Where LLDynamicArray is:


// class LLDynamicArray<>; // = std::vector + reserves <BlockSize> elements

template <typename Type, int BlockSize = 32>
class LLDynamicArray : public std::vector<Type>


Offending code: Method inside template class:

void reset() { std::vector<Type>::resize(0); }  

Type == FrameData.

If you checkout the code from Second Life trunk you will trigger this easily.
You will need other patches since they have other GCC 4.4 compile issues (minor
that I have fixed locally)

SVN is: http://svn.secondlife.com/svn/linden/trunk/


-- 

shawn dot starr at rogers dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |shawn dot starr at rogers
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2009-09-10 18:15 -------
  # VUSE <D.10497_132(D)>
  # aInstCtor_134 = VDEF <aInstCtor_133(D)>
  aInstCtor = D.10497;
  # VUSE <D.10496_135(D)>
  # aDataCtor_137 = VDEF <aDataCtor_136(D)>
  aDataCtor = D.10496;
  # VUSE <m_pInstance_138(D)>
  p_4 = m_pInstance;


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2009-09-10 18:18 -------
(In reply to comment #7)
>   # VUSE <D.10497_132(D)>
>   # aInstCtor_134 = VDEF <aInstCtor_133(D)>
>   aInstCtor = D.10497;
>   # VUSE <D.10496_135(D)>
>   # aDataCtor_137 = VDEF <aDataCtor_136(D)>
>   aDataCtor = D.10496;
>   # VUSE <m_pInstance_138(D)>
>   p_4 = m_pInstance;


  struct StaticInstanceWithInit D.10497;

Where StaticInstanceWithInit is an empty class except for a member function .

This should have been fixed by
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38908 but was not.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[gcc at abeckmann dot de]

------- Comment #9 from gcc at abeckmann dot de  2009-10-16 11:05 -------
Created an attachment (id=18809)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18809&action=view)
different test case

I've seen this spurious warning, too, and could reduce it to a different, much
smaller test case.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[gcc at abeckmann dot de]

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------- Comment #10 from gcc at abeckmann dot de  2009-10-16 13:11 -------
=== compile command (shows the spurious warning) ===
x86_64-linux-gnu-g++-4.4.x -O2 -W -Wall -DSPURIOUS_WARNING -c
anonymous-iuuitf.cpp
=== ===

=== compile command (no spurious warning) ===
x86_64-linux-gnu-g++-4.4.x -O2 -W -Wall -c anonymous-iuuitf.cpp
=== ===

=== spurious warning reported: ===
anonymous-iuuitf.cpp: In function ‘(static initializers for
anonymous-iuuitf.cpp)’:
anonymous-iuuitf.cpp:45: warning: ‘<anonymous>’ is used uninitialized in this
function
=== ===

The spurious warning also occurs with a i686 4.4.x compiler.
It does not happen with 4.3.x or trunk/4.5.x (both x86_64 and i686).
The warning also disappears if optimization is reduced from -O2 to -O1.

=== verbose output ===
$ x86_64-linux-gnu-g++-4.4.x -v -O2 -W -Wall -DSPURIOUS_WARNING -c
anonymous-iuuitf.cpp

Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4_4-branch/configure
--prefix=/opt/software/x86_64/gcc-4.4.x --program-suffix=-4.4.x
--enable-languages=c,c++ --enable-checking
Thread model: posix
gcc version 4.4.3 20091016 (prerelease) (GCC)
COLLECT_GCC_OPTIONS='-v' '-O2' '-W' '-Wall' '-DSPURIOUS_WARNING' '-c'
'-shared-libgcc' '-mtune=generic'

/opt/software/x86_64/gcc-4.4.x/libexec/gcc/x86_64-unknown-linux-gnu/4.4.3/cc1plus
-quiet -v -D_GNU_SOURCE -DSPURIOUS_WARNING anonymous-iuuitf.cpp -quiet
-dumpbase anonymous-iuuitf.cpp -mtune=generic -auxbase anonymous-iuuitf -O2 -W
-Wall -version -o /tmp/ccrjG8Y8.s
ignoring nonexistent directory
"/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../../include/c++/4.4.3

/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../../include/c++/4.4.3/x86_64-unknown-linux-gnu

/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../../include/c++/4.4.3/backward
 /usr/local/include
 /opt/software/x86_64/gcc-4.4.x/include
 /opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/include

/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/include-fixed
 /usr/include
End of search list.
GNU C++ (GCC) version 4.4.3 20091016 (prerelease) (x86_64-unknown-linux-gnu)
        compiled by GNU C version 4.4.3 20091016 (prerelease), GMP version
4.3.1, MPFR version 2.4.1-p2.
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 2f5c889faec03641af0e9a45c39b0565
anonymous-iuuitf.cpp: In function ‘(static initializers for
anonymous-iuuitf.cpp)’:
anonymous-iuuitf.cpp:45: warning: ‘<anonymous>’ is used uninitialized in this
function
COLLECT_GCC_OPTIONS='-v' '-O2' '-W' '-Wall' '-DSPURIOUS_WARNING' '-c'
'-shared-libgcc' '-mtune=generic'
 as -V -Qy -o anonymous-iuuitf.o /tmp/ccrjG8Y8.s
GNU assembler version 2.19.91 (x86_64-linux-gnu) using BFD version (GNU
Binutils for Debian) 2.19.91.20091006
COMPILER_PATH=/opt/software/x86_64/gcc-4.4.x/libexec/gcc/x86_64-unknown-linux-gnu/4.4.3/:/opt/software/x86_64/gcc-4.4.x/libexec/gcc/x86_64-unknown-linux-gnu/4.4.3/:/opt/software/x86_64/gcc-4.4.x/libexec/gcc/x86_64-unknown-linux-gnu/:/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/:/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/:/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/opt/software/x86_64/gcc-4.4.x/lib/gcc/x86_64-unknown-linux-gnu/4.4.3/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-O2' '-W' '-Wall' '-DSPURIOUS_WARNING' '-c'
'-shared-libgcc' '-mtune=generic'
=== ===


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[matt at use dot net]

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------- Comment #11 from matt at use dot net  2010-01-10 22:01 -------
I get this same problem when compiling scummvm (http://scummvm.org) on Ubuntu
9.10/amd64 using the default GCC 4.4.1:

g++ -O1 -finline-small-functions -finline-functions
-Wp,-MMD,"engines/sci/.deps/console.d",-MQ,"engines/sci/console.o",-MP -Wall
-Werror -g -ansi -W -Wno-unused-parameter -Wno-empty-body -pedantic
-Wno-long-long -Wno-multichar -Wno-unknown-pragmas -Wno-reorder
-fno-strict-aliasing  -Wpointer-arith -Wcast-qual -Wcast-align -Wshadow
-Wimplicit -Wnon-virtual-dtor -Wwrite-strings -fno-rtti -fno-exceptions
-fcheck-new -Wuninitialized -DSCUMMVM_SVN_REVISION=\"47235\" -DHAVE_CONFIG_H
-DUNIX -DDATA_PATH=\"/usr/local/share/scummvm\"
-DPLUGIN_DIRECTORY=\"/usr/local/lib/scummvm\" -DSDL_BACKEND
-DENABLE_SCUMM=STATIC_PLUGIN -DENABLE_SCUMM_7_8 -DENABLE_HE
-DENABLE_AGI=STATIC_PLUGIN -DENABLE_AGOS=STATIC_PLUGIN -DENABLE_AGOS2
-DENABLE_CINE=STATIC_PLUGIN -DENABLE_CRUISE=STATIC_PLUGIN
-DENABLE_DRACI=STATIC_PLUGIN -DENABLE_DRASCULA=STATIC_PLUGIN
-DENABLE_GOB=STATIC_PLUGIN -DENABLE_GROOVIE=STATIC_PLUGIN -DENABLE_GROOVIE2
-DENABLE_KYRA=STATIC_PLUGIN -DENABLE_LOL -DENABLE_LURE=STATIC_PLUGIN
-DENABLE_M4=STATIC_PLUGIN -DENABLE_MADE=STATIC_PLUGIN
-DENABLE_MOHAWK=STATIC_PLUGIN -DENABLE_PARALLACTION=STATIC_PLUGIN
-DENABLE_QUEEN=STATIC_PLUGIN -DENABLE_SAGA=STATIC_PLUGIN -DENABLE_IHNM
-DENABLE_SAGA2 -DENABLE_SCI=STATIC_PLUGIN -DENABLE_SCI32
-DENABLE_SKY=STATIC_PLUGIN -DENABLE_SWORD1=STATIC_PLUGIN
-DENABLE_SWORD2=STATIC_PLUGIN -DENABLE_TEENAGENT=STATIC_PLUGIN
-DENABLE_TINSEL=STATIC_PLUGIN -DENABLE_TOUCHE=STATIC_PLUGIN
-DENABLE_TUCKER=STATIC_PLUGIN -I. -I. -I./engines -I/usr/include/SDL
-D_GNU_SOURCE=1 -D_REENTRANT -c engines/sci/console.cpp -o
engines/sci/console.o
cc1plus: warnings being treated as errors
In file included from ./common/array.h:29,
                 from ./common/fs.h:28,
                 from ./engines/engine.h:30,
                 from ./engines/sci/sci.h:29,
                 from engines/sci/console.cpp:28:
./common/algorithm.h: In function ‘void Common::sort(T, T, StrictWeakOrdering)
[with T = Common::ListInternal::Iterator<Sci::ResourceId>, StrictWeakOrdering =
Sci::ResourceIdLess]’:
./common/algorithm.h:207: error: ‘<anonymous>’ may be used uninitialized in
this function
./common/algorithm.h:207: error: ‘<anonymous>’ may be used uninitialized in
this function
./common/algorithm.h:208: error: ‘<anonymous>’ may be used uninitialized in
this function
./common/algorithm.h:208: error: ‘<anonymous>’ may be used uninitialized in
this function
./common/algorithm.h:207: error: ‘<anonymous>’ may be used uninitialized in
this function
./common/algorithm.h:208: error: ‘<anonymous>’ may be used uninitialized in
this function


The issue does not occur with gcc-4.3 or gcc-4.5.20091228. I noticed the issue
when compiling with -O3, but reduced it to the above commandline. (Something
undocumented must happen at -O1, because putting the individual options for -O1
on the commandline  didn't reproduce the issue.)

Pre-processed sources are attached.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[matt at use dot net]

------- Comment #12 from matt at use dot net  2010-01-10 23:29 -------
Created an attachment (id=19533)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19533&action=view)
pre-processed output of the file that emitted the false positive using the
commandline mentioned in my comment


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[manu at gcc dot gnu dot org]

------- Comment #13 from manu at gcc dot gnu dot org  2010-01-11 18:39 -------
If this doesn't occur in GCC 4.5, the best we can do is to put the testcases in
the testsuite and close this. Many things changed from 4.4. to 4.5 that may
have cause the bug to disappear and that won't be backported, so even looking
for them would be a waste of developer's time.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[caolanm at redhat dot com]

------- Comment #14 from caolanm at redhat dot com  2010-07-13 14:37 -------
Checking with gcc 4.5, this works fine for me now, so I'm happy to call this
fixed in 4.5.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146

[Bug c++/40146] Unexplained "'<anonymous>' is used uninitialized in this function" warning

[manu at gcc dot gnu dot org]

------- Comment #15 from manu at gcc dot gnu dot org  2010-07-13 15:22 -------
Before closing this, please check all testcases provided and add at least one
of them to the testsuite.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40146