Re: [PULL 00/53] Misc patches for QEMU 5.1 soft freeze

[Claudio Fontana]

On 7/8/20 7:03 PM, Claudio Fontana wrote:
> On 7/8/20 6:55 PM, Paolo Bonzini wrote:
>> On 08/07/20 18:45, Claudio Fontana wrote:
>>> C++ is used to link the final qemu-system binary and on my system c++ has 
>>> LTO:
>>>
>>> c++ -v
>>> Using built-in specs.
>>> COLLECT_GCC=c++
>>> COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/7/lto-wrapper
>>> OFFLOAD_TARGET_NAMES=hsa:nvptx-none
>>> Target: x86_64-suse-linux
>>> Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
>>> --mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
>>> --enable-languages=c,c++,objc,fortran,obj-c++,ada,go
>>> --enable-offload-targets=hsa,nvptx-none=/usr/nvptx-none,
>>> --without-cuda-driver --enable-checking=release --disable-werror
>>> --with-gxx-include-dir=/usr/include/c++/7 --enable-ssp --disable-libssp
>>> --disable-libvtv --disable-libcc1 --disable-plugin
>>> --with-bugurl=https://bugs.opensuse.org/ --with-pkgversion='SUSE Linux' 
>>> --with-slibdir=/lib64 --with-system-zlib --enable-libstdcxx-allocator=new 
>>> --disable-libstdcxx-pch --enable-version-specific-runtime-libs 
>>> --with-gcc-major-version-only --enable-linker-build-id --enable-linux-futex 
>>> --enable-gnu-indirect-function --program-suffix=-7 
>>> --without-system-libunwind --enable-multilib --with-arch-32=x86-64 
>>> --with-tune=generic --build=x86_64-suse-linux --host=x86_64-suse-linux
>>> Thread model: posix
>>> gcc version 7.5.0 (SUSE Linux) 
>>>
>>>
>>> I checked cc but did not think to check c++ . I will find a way to disable 
>>> this thing and will correct the patch accordingly.
>>
>> Having LTO support is not the same thing as having it enabled.  Are you
>> compiling and linking with "-flto"?
>>
>> Paolo
>>
> 
> no, the compilation and link stage do not show this explicit parameter. I am 
> puzzled.
> 
> C
> 

This is really weird, as I cannot reproduce it.

What I did notice is that all the code that directly or indirectly uses the 
functions is under an

if (0) (
)

since tcg_enabled is the constant 0.

By "indirectly" I mean that the static void qemu_tcg_cpu_thread_fn() function 
that calls those is referenced only by static void qemu_tcg_init_vcpu(), which 
is called only under an if (0),
ie if (tcg_enabled()).

For me this builds with --disable-tcg and with --enable-tcg .

Maybe the issue is actually the name clash of the stub and the module?

I admit I am not familiar with the rationale of why the stubs are all built 
regardless, could we have that icount.o from stubs/ is replacing 
softmmu/icount.o to cause this?

Thanks,

Claudio