On Wed, 15 Mar 2023 at 22:17, Jonathan Wakely <jwak...@redhat.com> wrote:
> > > On Wed, 15 Mar 2023 at 22:14, Ben Beasley <c...@musicinmybrain.net> wrote: > >> Thank you for prompting me to look at this more closely. A quick >> investigation reveals: >> >> “Abseil libraries require C++14 as the current minimum standard. When >> compiled with C++17 (either because it is the compiler's default or >> explicitly requested), then Abseil requires C++17.” >> >> >> https://github.com/abseil/abseil-cpp/blob/20230125.1/CMake/AbseilHelpers.cmake#L291 >> >> The abseil-cpp package in Fedora has been compiled as C++17 for some >> time—at first explicitly, but this would also now be the default if the >> spec file did not configure a particular standard—so it seems dependent >> packages already technically needed C++17, and it is mere happenstance that >> this particular release is revealing incompatibilities. >> > > I'm not sure if that's true, see my other email which crossed with yours. > In the previous release absl::string_view would work for both C++14 and > C++17, because USE_STD_STRING_VIEW was defined to 2, so adapted to the > headers that included it. > > In the new release it is hardcoded to only work for C++17. That seems like > a new change in the new version, not something that was already present. > Digging deeper, maybe it was true, and ilbc was just getting away with it by chance. Several member functions of absl::string_view are defined out-of-line in abseil-cpp-20220623.1/absl/strings/string_view.cc but if the library is built as C++17 then those won't be defined (because absl::string_view is just an alias for std::string_view, so all the members come from libstdc++). So all clients of abseil-cpp shared libs do need to be compiled as C++17 or later. It looks like libilbc.so.3.0.4 doesn't actually use any libasbl_*.so libs, so only uses libabsl headers, and that's why it "worked" when the header was adaptive w.r.t. the string-view definition. It doesn't care that there are no definitions for those string_view member functions, because it happens to not use those specific member functions.
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