Re: Lost ELF library auto-provides since mass rebuild

[Jeff Law]

On Thu, 2020-08-06 at 17:04 +0200, Florian Weimer wrote:
>  * Daniel P. Berrangé:
>  
>  > This is in relation to this bug
>  > 
>  > https://bugzilla.redhat.com/show_bug.cgi?id=1862745
>  > 
>  > The last but one build of libgphoto have auto-provides for the ELF
>  > libraries:
>  > 
>  > libgphoto2 = 2.5.24-2.fc33
>  > libgphoto2(x86-64) = 2.5.24-2.fc33
>  > libgphoto2.so.6()(64bit)
>  > libgphoto2_port.so.12()(64bit)
>  > libgphoto2_port.so.12(LIBGPHOTO2_5_0)(64bit)
>  > libgphoto2_port.so.12(LIBGPHOTO2_INTERNAL)(64bit)
>  > 
>  > any new build both in the mass rebuild and any scratch builds I try
>  > looses some of these auto deps leaving just
>  > 
>  > libgphoto2 = 2.5.24-3.fc33
>  > libgphoto2(x86-64) = 2.5.24-3.fc33
>  > libgphoto2.so.6()(64bit)
>  > libgphoto2_port.so.12()(64bit)
>  > 
>  > 
>  > Was there any change people are aware of that would explain this and
>  > suggest what we need todo to get these deps back in libghoto ?
>  
>  I think this isn't the real issue.  As far as I can tell, all the symbol
>  versioning information is gone.  The RPM dependencies are correct, but
>  the ABI is not. 8-p
>  
>  configure.ac has this:
>  
>  AC_MSG_CHECKING([for asm .symver support])
>  AC_COMPILE_IFELSE([dnl
>          AC_LANG_PROGRAM([[]],[[
>                  int f1() { }
>                  int f2() { }
>                  asm(".symver f1, f@VER1");
>                  asm(".symver f2, f@@VER2");
>                  int main(int argc, char **argv) { }
>          ]])dnl
>  ],[
>          AC_DEFINE([HAVE_ASM_SYMVERS],1,[Define if there is asm .symver support.])
>          VERSIONMAPLDFLAGS="-Wl,--version-script=\$(srcdir)/libgphoto2.ver"
>          AC_MSG_RESULT(yes)
>  ],[
>          VERSIONMAPLDFLAGS=""
>          AC_MSG_RESULT(no)
>  ])
>  AC_SUBST(VERSIONMAPLDFLAGS)
>  
>  And build.log shows:
>  
>  checking for asm .symver support... no
>  
>  The HAVE_ASM_SYMVERS macro is apparently unused, but setting
>  VERSIONMAPLDFLAGS looks *very* relevant.
>  
>  The cause seems to be this:
>  
>  /tmp/ccAbnnro.s: Assembler messages:
>  /tmp/ccAbnnro.s: Error: invalid attempt to declare external version name
>  as default in symbol `f@@VER2'
>  
>  It's LTO-related in the sense that f1 & f2 get different symbols with
>  LTO.  This fixes the test:
>  
>                  int __attribute__ ((externally_visible)) f1() { }
>                  int __attribute__ ((externally_visible)) f2() { }
>                  asm(".symver f1, f@VER1");
>                  asm(".symver f2, f@@VER2");
>                  int main(int argc, char **argv) { }
>  
>  Not sure this was missed by Jeff's config.log differ.  Maybe its
>  binutils version was too old? 
This package needs to opt-out of LTO.

libgphoto2 passed its control and LTO builds as well as the config.h check.  So
I'm not sure what went wrong here.

jeff