Remove the LTO warning for ENABLE_MASON builds #3481
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Arch Linux is the only platform we know about not compiling with mason and lto because @TheMarex is running it, right? Why not leave the warning in then, until we fix it for all systems? |
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When setting on source compilation on an Ubuntu 14.04 box using the ubuntu testing toolchain and clang-3.8 from the llvm PPA I had similar problems. I can try to reproduce this in a docker container, but there is definitely something weird going on with different binuitils/clang/libstdc++ combinations. |
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This is a clang bug and not an issue with OSRM or mason as noted at #3501 (comment). My preference would be to disable LTO by default, then keep this warning in place. Thoughts? |
@TheMarex please ticket when you have more details. |
Users don't care who is to blame here - if the default installation instructions for OSRM result in segfaults we're doing something wrong. I will update the installation instructions to use Clang 3.9.1 and also disable LTO now by default. LTO is still resulting in segfaults and linker errors from time to time on some platforms and some compiler + binutils combinations. Not recommended by default, unless you know what you're doing and need the performance. |
This disables the `-flto` LTO flag by default since we're seeing segfaults in compiler lto plugins, binutils and linker errors again and again for various clang / gcc / binutils combinations. Pass `-DNEBALE_LTO` to `cmake` in order to re-enable LTO. LTO situation in short: - LTO does not work at all for gcc<4.9 - With gcc>=4.9 the "slim" LTO format is getting used dumping IR - Older binutils need LTO plugins which know how to read this IR - Recent binutils handle this format all by themselves - LLVM is more or less the same with some Clang versions segfaulting If you need the performance benefit of LTO, make sure your compiler and binutils are up to date and see for yourself if LTO builds work for you. References: - https://gcc.gnu.org/wiki/LinkTimeOptimizationFAQ - #3481 (comment) - #3501 - #3441 (and a ton of other LTO tickets if you search for them)
This disables the `-flto` LTO flag by default since we're seeing segfaults in compiler lto plugins, binutils and linker errors again and again for various clang / gcc / binutils combinations. Pass `-DNEBALE_LTO` to `cmake` in order to re-enable LTO. LTO situation in short: - LTO does not work at all for gcc<4.9 - With gcc>=4.9 the "slim" LTO format is getting used dumping IR - Older binutils need LTO plugins which know how to read this IR - Recent binutils handle this format all by themselves - LLVM is more or less the same with some Clang versions segfaulting If you need the performance benefit of LTO, make sure your compiler and binutils are up to date and see for yourself if LTO builds work for you. References: - https://gcc.gnu.org/wiki/LinkTimeOptimizationFAQ - #3481 (comment) - #3501 - #3441 (and a ton of other LTO tickets if you search for them)
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LTO is off by default with #3524 - let's keep this warning. Users will only see it if they enable lto and are using mason. |
This PR removes a warning that is only known to be helpful for arch users that enable LTO (#3480) and warns unnecessary for ubuntu versions built per the wiki (https://github.com/Project-OSRM/osrm-backend/wiki/Building-on-Ubuntu). I think the noise of this warning is just not worth it, so this removes it.