Fix alignment issues in Clang.
Some const-correctness changes snuck in here too, since they were in the
area of code I was modifying.
This seems to make Clang actually work without Bus Error on
32bit-sparc.
Follow-up patches will factor out a trailing-object helper class, to
make classes using the idiom of appending objects to other objects
easier to understand, and to ensure (with static_assert) that required
alignment guarantees continue to hold.
Differential Revision: http://reviews.llvm.org/D10272
llvm-svn: 242554
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 4fcec53..e772f19 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -45,10 +45,19 @@
getASTContext().getExternalSource()->updateOutOfDateIdentifier(II);
}
+#define DECL(DERIVED, BASE) \
+ static_assert(Decl::DeclObjAlignment >= \
+ llvm::AlignOf<DERIVED##Decl>::Alignment, \
+ "Alignment sufficient after objects prepended to " #DERIVED);
+#define ABSTRACT_DECL(DECL)
+#include "clang/AST/DeclNodes.inc"
+
void *Decl::operator new(std::size_t Size, const ASTContext &Context,
unsigned ID, std::size_t Extra) {
// Allocate an extra 8 bytes worth of storage, which ensures that the
- // resulting pointer will still be 8-byte aligned.
+ // resulting pointer will still be 8-byte aligned.
+ static_assert(sizeof(unsigned) * 2 >= DeclObjAlignment,
+ "Decl won't be misaligned");
void *Start = Context.Allocate(Size + Extra + 8);
void *Result = (char*)Start + 8;
@@ -69,7 +78,13 @@
// With local visibility enabled, we track the owning module even for local
// declarations.
if (Ctx.getLangOpts().ModulesLocalVisibility) {
- void *Buffer = ::operator new(sizeof(Module *) + Size + Extra, Ctx);
+ // Ensure required alignment of the resulting object by adding extra
+ // padding at the start if required.
+ size_t ExtraAlign =
+ llvm::OffsetToAlignment(sizeof(Module *), DeclObjAlignment);
+ char *Buffer = reinterpret_cast<char *>(
+ ::operator new(ExtraAlign + sizeof(Module *) + Size + Extra, Ctx));
+ Buffer += ExtraAlign;
return new (Buffer) Module*(nullptr) + 1;
}
return ::operator new(Size + Extra, Ctx);