[mythtv] Strange distribution-dependent build error

[Paul Gardiner]

On 13/08/2025 01:25, Scott Theisen wrote:
> On 2025/08/12 08:38, Paul Gardiner wrote:
>> On 06/08/2025 20:44, Scott Theisen wrote:
>>> On 2025/08/06 06:17, Paul Gardiner wrote:
>>>> I have a .spec file that builds mythtv packages for opensuse leap. 
>>>> I've been using it for several years, needing to make only small 
>>>> changes from time to time as leap has moved through various 
>>>> versions. Surprisingly to me, I get this error when I try to use the 
>>>> same .spec file for opensuse tumbleweed:
>>>>
>>>> [  238s] /usr/lib64/gcc/x86_64-suse-linux/13/../../../../x86_64- 
>>>> suse- linux/bin/ld: /tmp/ccf31tRw.ltrans115.ltrans.o: warning: 
>>>> relocation against `pd_1' in read-only section `.text'
>>>> [  238s] /usr/lib64/gcc/x86_64-suse-linux/13/../../../../x86_64- 
>>>> suse- linux/bin/ld: /tmp/ccf31tRw.ltrans115.ltrans.o: relocation 
>>>> R_X86_64_PC32 against undefined symbol `pd_1' can not be used when 
>>>> making a shared object; recompile with -fPIC
>>>>
>>>> This seems to relate to a piece of inline assembly code in mythtv/ 
>>>> mythtv/external/FFmpeg/libavcodec/x86/lpc_init.c. I thought -fPIC 
>>>> didn't affect inline assemble, and in any case, I'd imagine that the 
>>>> flags are consistent between leap and tumbleweed.
>>>>
>>>> I'm struggling to find a way forward. Any thoughts?
>>>>
>>>> Cheers,
>>>>     Paul.
>>>
>>> Both configure and CMake run FFmpeg/configure with --enable-pic, so 
>>> that is strange since it should already compile with -fPIC.
>>>
>>> How do FFmpeg/config.h and FFmpeg/ffbuild/config.mak differ between 
>>> the two builds?  In particular, what are the values of 
>>> FFMPEG_CONFIGURATION, CPPFLAGS, and CFLAGS?
>>
>> There were differences, which surprised me - perhaps it shouldn't. The 
>> failing case included -flto=auto. I added -fno-lto and that avoided 
>> the error. Possibly adding -fno-lto isn't the best fix. I wonder if 
>> somehow -fPIC is added to the compiler flags, but not the link flags. 
>> Still, I have something that works.
>>
>> Thanks for your help.
> 
> Adding -fno-lto will disable LTO, but where is -flto=auto coming from? 
> CMake doesn't compile FFmpeg with LTO and `configure --enable-lto` adds 
> -flto not -flto=auto.


The opensuse build service suggests adding

CFLAGS="%{optflags}";export CFLAGS;
CXXFLAGS="%{optflags}";export CXXFLAGS;

to the .spec file. I just followed their instructions, my having little 
knowledge of which flags I should add. The strategy had seemingly been 
working up to now.