Re: Compliling Xen 4.5.0 Fails with error: ‘bufioreq_pfn’ may be used uninitialised in this function [-Werror=uninitialized]

[Ian Murray <murrayie@yahoo.co.uk>]

----- Original Message -----
> From: Paul Durrant <Paul.Durrant@citrix.com>
> To: Ian Murray <murrayie@yahoo.co.uk>; "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
> Cc: 
> Sent: Monday, 16 March 2015, 9:45
> Subject: Re: [Xen-devel] Compliling Xen 4.5.0 Fails with error: ‘bufioreq_pfn’ may be used uninitialised in this function  [-Werror=uninitialized]
> 
>>  -----Original Message-----
>>  From: xen-devel-bounces@lists.xen.org [mailto:xen-devel-
>>  bounces@lists.xen.org] On Behalf Of Ian Murray
>>  Sent: 15 March 2015 22:59
>>  To: xen-devel@lists.xensource.com
>>  Subject: [Xen-devel] Compliling Xen 4.5.0 Fails with error: ‘bufioreq_pfn’ 
> may
>>  be used uninitialised in this function [-Werror=uninitialized]
>> 
>>  Hi,
>> 
>>  This was originally posted to the user list but it was suggested to me to 
> post it
>>  here also. I am getting a failed compilation when I try to compile Xen 
> 4.5.0
>>  from the tarball and also from Git. I can compile RC4, although a bisect
>>  reveals that they pertinent difference is debug=y in Config.mk, which 
> allows
>>  it to compile. That compiles without a problem and that is what I am 
> running
>>  with. I have tried to build on two different servers with the same result,
>>  however both are running Ubuntu 12.04.5 and are similarly configured.
>> 
>>  Steps I (would) use to build are simply...
>> 
>>  ./configure
>>  make dist
>>  make install
>> 
>> 
>>  which results in...
>> 
>>  ...
>>  gcc -O2 -fomit-frame-pointer -m64 -fno-strict-aliasing -std=gnu99 -Wall
>>  -Wstrict-prototypes -Wdeclaration-after-statement -Wno-unused-but-set-
>>  variable
>>  -DNDEBUG -I/root/xen450/xen-4.5.0/xen/include
>>  -I/root/xen450/xen-4.5.0/xen/include/asm-x86/mach-generic
>>  -I/root/xen450/xen-4.5.0/xen/include/asm-x86/mach-default -msoft-float
>>  -fno-stack-protector -fno-exceptions -Wnested-externs -DHAVE_GAS_VMX
>>  -DHAVE_GAS_EPT -DHAVE_GAS_FSGSBASE -mno-red-zone -mno-sse -fpic
>>  -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE -fno-
>>  builtin
>>  -fno-common -Werror -Wredundant-decls -Wno-pointer-arith -pipe -g -
>>  D__XEN__
>>  -include /root/xen450/xen-4.5.0/xen/include/xen/config.h -nostdinc -
>>  DHAS_ACPI
>>  -DHAS_GDBSX -DHAS_PASSTHROUGH -DHAS_MEM_ACCESS -
>>  DHAS_MEM_PAGING
>>  -DHAS_MEM_SHARING -DHAS_PCI -DHAS_IOPORTS -DHAS_PDX -MMD -MF
>>  .hvm.o.d -c hvm.c
>>  -o hvm.o
>>  hvm.c: In function ‘hvm_create_ioreq_server’:
>>  hvm.c:487:18: error: ‘bufioreq_pfn’ may be used uninitialised in this 
> function
>>  [-Werror=uninitialized]
>>  hvm.c:718:30: note: ‘bufioreq_pfn’ was declared here
>>  cc1: all warnings being treated as errors
>>  make[5]: *** [hvm.o] Error 1
>> 
>>  Any suggestions are welcome,
>> 
> 
> Those line numbers don't work for me. I did a checkout of RELEASE-4.5.0 and, 
> whilst bufioreq_pfn is indeed declared on line 718, I see no reference to it on 
> line 487. Also, if I compile debug=n I see no problem. Is it possible you 
> don't have a clean checkout of 4.5.0? What version of gcc are you using?
> 
>   Paul
>

Thanks for replying.

# gcc --version
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3

This is both from a brand new clone of Git and also the release tarball. Ian C has commented elsewhere about what the compiler might be up to, although it's beyond my knowledge in terms of how "clever" the compiler is being. FWIW, I couldn't really understand the line numbering, so I looked at the files themselves and couldn't see a direct, either.... and surely the variable in question is well out of scope at that point. (obviously I am being naive about something here.)





  
> 
>>  Thanks for reading,
>> 
>>  Ian.
>> 
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