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[objc] Use references to Obj C classes instead of names in descriptors. #7026

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merged 1 commit into from
Jan 15, 2020
Merged

[objc] Use references to Obj C classes instead of names in descriptors. #7026

merged 1 commit into from
Jan 15, 2020

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dmaclach
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@dmaclach dmaclach commented Dec 18, 2019 •
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This switches the compiler and library to use objective-c class references instead of class names (that are resolved using objc_getClass/NSClassFromString).

This should:

  1. Reduce binary size slightly as we no longer need the strings.
  2. Add a small performance improvement as we no longer need to look up classes.
  3. Help enforce proper linkage by having actual class references for the linker to resolve. In cases where we are linking static archives there were cases where some of the Objective-C classes were not being pulled into the linkage requiring the use of the -ObjC linker flag (or other linker tricks). There are some other places in the code that we need to do this to get full coverage, but this is a good start.

@thomasvl thomasvl self-assigned this Dec 19, 2019
dmaclach
dmaclach commented Dec 19, 2019
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PTAL

thomasvl
thomasvl reviewed Dec 20, 2019
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dmaclach
dmaclach commented Dec 20, 2019
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Merged in the changes for extensions that I had previously promised would be a separate CL. It seems to make sense to have one CL for this. It's a little larger, but keeps all the changes together if/when things break :)

thomasvl
thomasvl approved these changes Dec 20, 2019
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thomasvl
thomasvl requested changes Jan 6, 2020
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Looks like use of asm is going to cause problem, see google/google-api-objectivec-client-for-rest#322 where this just came up.

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Looks like use of asm is going to cause problem, see google/google-api-objectivec-client-for-rest#322 where this just came up.

Check out latest patch. It should clear bitcode validation now as we are not declaring any new identifiers.

@dmaclach dmaclach force-pushed the classes branch 2 times, most recently from 145e97d to 7adc675 Compare January 10, 2020 21:46
@dmaclach
Use references to Objective C classes instead of looking classes up b…
bffe695 
…y name.

This should reduce binary size slightly, small performance improvement, and improve linkage by forcing references to all used classes.

Note that this maintains backwards compatibility for sources generated by older protoc for the time being. If you want the benefits
you will need to recompile your protos with the newer protoc.
@thomasvl thomasvl merged commit 74956e1 into protocolbuffers:master Jan 15, 2020
@dmaclach dmaclach deleted the classes branch January 22, 2020 18:22
@M1ke M1ke mentioned this pull request Jun 2, 2020
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