[cfe-commits] r154849 - in /cfe/trunk: lib/AST/ExprConstant.cpp test/Sema/const-eval.c

[Eli Friedman]

Author: efriedma
Date: Mon Apr 16 14:23:57 2012
New Revision: 154849

URL: http://llvm.org/viewvc/llvm-project?rev=154849&view=rev
Log:
Per Richard's comments on r154794, add the checks necessary to handle constant-folding relational comparisons safely in case the user is using -fwrapv or equivalent.


Modified:
    cfe/trunk/lib/AST/ExprConstant.cpp
    cfe/trunk/test/Sema/const-eval.c

Modified: cfe/trunk/lib/AST/ExprConstant.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=154849&r1=154848&r2=154849&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ExprConstant.cpp (original)
+++ cfe/trunk/lib/AST/ExprConstant.cpp Mon Apr 16 14:23:57 2012
@@ -5090,8 +5090,6 @@
 
       // The comparison here must be unsigned, and performed with the same
       // width as the pointer.
-      // FIXME: Knowing the base is the same for the LHS and RHS isn't enough
-      // for relational operators.
       unsigned PtrSize = Info.Ctx.getTypeSize(LHSTy);
       uint64_t CompareLHS = LHSOffset.getQuantity();
       uint64_t CompareRHS = RHSOffset.getQuantity();
@@ -5100,6 +5098,19 @@
       CompareLHS &= Mask;
       CompareRHS &= Mask;
 
+      // If there is a base and this is a relational operator, we can only
+      // compare pointers within the object in question; otherwise, the result
+      // depends on where the object is located in memory.
+      if (!LHSValue.Base.isNull() && E->isRelationalOp()) {
+        QualType BaseTy = getType(LHSValue.Base);
+        if (BaseTy->isIncompleteType())
+          return Error(E);
+        CharUnits Size = Info.Ctx.getTypeSizeInChars(BaseTy);
+        uint64_t OffsetLimit = Size.getQuantity();
+        if (CompareLHS > OffsetLimit || CompareRHS > OffsetLimit)
+          return Error(E);
+      }
+
       switch (E->getOpcode()) {
       default: llvm_unreachable("missing comparison operator");
       case BO_LT: return Success(CompareLHS < CompareRHS, E);

Modified: cfe/trunk/test/Sema/const-eval.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/const-eval.c?rev=154849&r1=154848&r2=154849&view=diff
==============================================================================
--- cfe/trunk/test/Sema/const-eval.c (original)
+++ cfe/trunk/test/Sema/const-eval.c Mon Apr 16 14:23:57 2012
@@ -125,3 +125,9 @@
 // <rdar://problem/10962435>
 EVAL_EXPR(45, ((char*)-1) + 1 == 0 ? 1 : -1)
 EVAL_EXPR(46, ((char*)-1) + 1 < (char*) -1 ? 1 : -1)
+EVAL_EXPR(47, &x < &x + 1 ? 1 : -1)
+EVAL_EXPR(48, &x != &x - 1 ? 1 : -1)
+EVAL_EXPR(49, &x < &x - 100 ? 1 : -1) // expected-error {{must have a constant size}}
+
+extern struct Test50S Test50;
+EVAL_EXPR(50, &Test50 < (struct Test50S*)((unsigned)&Test50 + 10)) // expected-error {{must have a constant size}}