Mercurial > hg
diff mercurial/cext/revlog.c @ 44066:f5d2720f3bea
revlog-native: introduced ABI version in capsule
Concerns that an inconsistency could arise between the actual contents
of the capsule in revlog.c and the Rust consumer have been raised after
the switch to the array of data and function pointers in f384d68d8ea8.
It has been suggested that the `version` from parsers.c could be use for
this. In this change, we introduce instead a separate ABI version number,
which should have the following advantages:
- no need to change the consuming Rust code for changes that have nothing
to do with the contents of the capsule
- the version number in parsers.c is not explicitely flagged as ABI. It's
not obvious to me whether an ABI change that would be invisible to Python
would warrant an increment
The drawback is that developers now have to consider two version numbers.
We expect the added cost of the check to be negligible because it occurs
at instantiation of `CIndex` only, which in turn is tied to instantiation
of Python objects such as `LazyAncestors` and `MixedIndex`. Frequent calls
to `Cindex::new` should also probably hit the CPU branch predictor.
Differential Revision: https://phab.mercurial-scm.org/D7856
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Tue, 14 Jan 2020 12:04:12 +0100 |
parents | f384d68d8ea8 |
children | 9db11679f8ac 864e9534d3d4 |
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--- a/mercurial/cext/revlog.c Mon Jan 13 19:11:44 2020 -0800 +++ b/mercurial/cext/revlog.c Tue Jan 14 12:04:12 2020 +0100 @@ -38,6 +38,7 @@ } nodetreenode; typedef struct { + int abi_version; int (*index_parents)(PyObject *, int, int *); } Revlog_CAPI; @@ -3037,6 +3038,9 @@ #endif /* WITH_RUST */ static Revlog_CAPI CAPI = { + /* increment the abi_version field upon each change in the Revlog_CAPI + struct or in the ABI of the listed functions */ + 1, HgRevlogIndex_GetParents, };