On Wed, 15 Mar 2023 at 22:17, Jonathan Wakely <jwakely@xxxxxxxxxx> wrote:
On Wed, 15 Mar 2023 at 22:14, Ben Beasley <code@xxxxxxxxxxxxxxxxxx> 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.
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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