Implement -Wcast-align. The initial design of this diagnostic diverges
from GCC's in that we warn on *any* increase in alignment requirements, not
just those that are enforced by hardware. Please let us know if this causes
major problems for you (which it shouldn't, since it's an optional warning).
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110959 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 7e1eebe..14c0d87 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -2796,3 +2796,48 @@
return HasInvalidParm;
}
+
+/// CheckCastAlign - Implements -Wcast-align, which warns when a
+/// pointer cast increases the alignment requirements.
+void Sema::CheckCastAlign(Expr *Op, QualType T, SourceRange TRange) {
+ // This is actually a lot of work to potentially be doing on every
+ // cast; don't do it if we're ignoring -Wcast_align (as is the default).
+ if (getDiagnostics().getDiagnosticLevel(diag::warn_cast_align)
+ == Diagnostic::Ignored)
+ return;
+
+ // Ignore dependent types.
+ if (T->isDependentType() || Op->getType()->isDependentType())
+ return;
+
+ // Require that the destination be a pointer type.
+ const PointerType *DestPtr = T->getAs<PointerType>();
+ if (!DestPtr) return;
+
+ // If the destination has alignment 1, we're done.
+ QualType DestPointee = DestPtr->getPointeeType();
+ if (DestPointee->isIncompleteType()) return;
+ CharUnits DestAlign = Context.getTypeAlignInChars(DestPointee);
+ if (DestAlign.isOne()) return;
+
+ // Require that the source be a pointer type.
+ const PointerType *SrcPtr = Op->getType()->getAs<PointerType>();
+ if (!SrcPtr) return;
+ QualType SrcPointee = SrcPtr->getPointeeType();
+
+ // Whitelist casts from cv void*. We already implicitly
+ // whitelisted casts to cv void*, since they have alignment 1.
+ // Also whitelist casts involving incomplete types, which implicitly
+ // includes 'void'.
+ if (SrcPointee->isIncompleteType()) return;
+
+ CharUnits SrcAlign = Context.getTypeAlignInChars(SrcPointee);
+ if (SrcAlign >= DestAlign) return;
+
+ Diag(TRange.getBegin(), diag::warn_cast_align)
+ << Op->getType() << T
+ << static_cast<unsigned>(SrcAlign.getQuantity())
+ << static_cast<unsigned>(DestAlign.getQuantity())
+ << TRange << Op->getSourceRange();
+}
+