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Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D145783
Files:
clang/include/clang-c/Index.h
clang/tools/libclang/CIndex.cpp
Index: clang/tools/libclang/CIndex.cpp
===================================================================
--- clang/tools/libclang/CIndex.cpp
+++ clang/tools/libclang/CIndex.cpp
@@ -3724,6 +3724,13 @@
// if (options->Size >= offsetof(CXIndexOptions, RecentlyAddedMember))
// do_something(options->RecentlyAddedMember);
+ // An exception: if a new option is small enough, it can be squeezed into the
+ // /*Reserved*/ bits in CXIndexOptions. Since the default value of each
option
+ // is guaranteed to be 0 and the callers are advised to zero out the struct,
+ // programs built against older libclang versions would implicitly set the
new
+ // options to default values, which should keep the behavior of previous
+ // libclang versions and thus be backward-compatible.
+
// If options->Size > sizeof(CXIndexOptions), the user may have set an option
// we can't handle, in which case we return nullptr to report failure.
// Replace `!=` with `>` here to support older struct versions. `!=` has the
Index: clang/include/clang-c/Index.h
===================================================================
--- clang/include/clang-c/Index.h
+++ clang/include/clang-c/Index.h
@@ -367,6 +367,7 @@
* \see clang_createIndex()
*/
unsigned DisplayDiagnostics : 1;
+ unsigned /*Reserved*/ : 14;
/**
* The path to a directory, in which to store temporary PCH files. If null or
* empty, the default system temporary directory is used. These PCH files are
Index: clang/tools/libclang/CIndex.cpp
===================================================================
--- clang/tools/libclang/CIndex.cpp
+++ clang/tools/libclang/CIndex.cpp
@@ -3724,6 +3724,13 @@
// if (options->Size >= offsetof(CXIndexOptions, RecentlyAddedMember))
// do_something(options->RecentlyAddedMember);
+ // An exception: if a new option is small enough, it can be squeezed into the
+ // /*Reserved*/ bits in CXIndexOptions. Since the default value of each option
+ // is guaranteed to be 0 and the callers are advised to zero out the struct,
+ // programs built against older libclang versions would implicitly set the new
+ // options to default values, which should keep the behavior of previous
+ // libclang versions and thus be backward-compatible.
+
// If options->Size > sizeof(CXIndexOptions), the user may have set an option
// we can't handle, in which case we return nullptr to report failure.
// Replace `!=` with `>` here to support older struct versions. `!=` has the
Index: clang/include/clang-c/Index.h
===================================================================
--- clang/include/clang-c/Index.h
+++ clang/include/clang-c/Index.h
@@ -367,6 +367,7 @@
* \see clang_createIndex()
*/
unsigned DisplayDiagnostics : 1;
+ unsigned /*Reserved*/ : 14;
/**
* The path to a directory, in which to store temporary PCH files. If null or
* empty, the default system temporary directory is used. These PCH files are
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