[llvm-dev] ABI change in LLVM 7.0.x release (original) (raw)

Kristina Brooks via llvm-dev llvm-dev at lists.llvm.org
Wed Dec 5 06:54:40 PST 2018

Hi,

While on topic of ABI changes, could I request that this (only the first part which bumped the constant number up for OS targets) be merged into an ABI breaking release?

https://reviews.llvm.org/rL347832

This is only the LLVMSupport part of the patch, the Clang half depends on it but that is more of a feature thing so it's better left for 8.x.x. I'm mentioning this because there was some confusion w/r Debian merging this patch into their 7.x.x fork before it went into trunk which caused ABI breakage for anyone who relied on the last enum member to determine the size.

Thank you.

Hans Wennborg via llvm-dev wrote:

On Tue, Dec 4, 2018 at 7:43 PM Tom Stellard <tstellar at redhat.com> wrote:

Hi, Fixing http://llvm.org/PR39427 in the release70 branch, will change the ABI of a clang built libLLVM-7.so so that it is no longer compatible with the 7.0.0 release. libLLVM-7.so built by gcc will not be affected by this fix. Changing the ABI is something we aren't supposed to do in stable releases, but this fixes an ABI difference between clang and gcc built libLLVM-7.so that is impacting many users, including Linux distributions, so an ABI change for clang only seems like the least bad solution in this case. I am proposing that we hold this fix out of 7.0.1 and instead ship it in a special 7.0.2 (or maybe 7.1.0 ?) release, so that users that want to are still able to get all the bug-fixes without the ABI changes. How does this sound to everyone? I think this sounds reasonable. The important thing is that the fix gets shipped, and if we do e.g. both 7.0.1 and 7.0.2 (I'm not sure what version numbers would be best to use) that should hopefully serve everyone well. Thanks, Hans

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