Implement rdar://6319320: give a good diagnostic for cases where people
are trying to use the old GCC "casts as lvalue" extension. We don't and
will hopefully never support this.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59460 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/Expr.h b/include/clang/AST/Expr.h
index 6e67f28..030a399 100644
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@@ -99,6 +99,7 @@
MLV_IncompleteVoidType,
MLV_DuplicateVectorComponents,
MLV_InvalidExpression,
+ MLV_LValueCast, // Specialized form of MLV_InvalidExpression.
MLV_IncompleteType,
MLV_ConstQualified,
MLV_ArrayType,
diff --git a/include/clang/Basic/DiagnosticKinds.def b/include/clang/Basic/DiagnosticKinds.def
index 692d01d8..d1f7231 100644
--- a/include/clang/Basic/DiagnosticKinds.def
+++ b/include/clang/Basic/DiagnosticKinds.def
@@ -1225,6 +1225,8 @@
"expression is not assignable")
DIAG(err_typecheck_incomplete_type_not_modifiable_lvalue, ERROR,
"incomplete type '%0' is not assignable")
+DIAG(err_typecheck_lvalue_casts_not_supported, ERROR,
+ "assignment to cast is illegal, lvalue casts are not supported")
DIAG(err_typecheck_duplicate_vector_components_not_mlvalue, ERROR,
"vector is not assignable (contains duplicate components)")
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 29d9a11..d2c9ea9 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -495,7 +495,15 @@
case LV_NotObjectType: return MLV_NotObjectType;
case LV_IncompleteVoidType: return MLV_IncompleteVoidType;
case LV_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
- case LV_InvalidExpression: return MLV_InvalidExpression;
+ case LV_InvalidExpression:
+ // If the top level is a C-style cast, and the subexpression is a valid
+ // lvalue, then this is probably a use of the old-school "cast as lvalue"
+ // GCC extension. We don't support it, but we want to produce good
+ // diagnostics when it happens so that the user knows why.
+ if (const CStyleCastExpr *CE = dyn_cast<CStyleCastExpr>(this))
+ if (CE->getSubExpr()->isLvalue(Ctx) == LV_Valid)
+ return MLV_LValueCast;
+ return MLV_InvalidExpression;
}
QualType CT = Ctx.getCanonicalType(getType());
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index a5066a8..0506b40 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -2345,6 +2345,10 @@
Diag(loc, diag::err_typecheck_non_object_not_modifiable_lvalue,
lhsType.getAsString(), lex->getSourceRange());
return QualType();
+ case Expr::MLV_LValueCast:
+ Diag(loc, diag::err_typecheck_lvalue_casts_not_supported,
+ lex->getSourceRange());
+ return QualType();
case Expr::MLV_InvalidExpression:
Diag(loc, diag::err_typecheck_expression_not_modifiable_lvalue,
lex->getSourceRange());
diff --git a/test/Sema/block-misc.c b/test/Sema/block-misc.c
index 62b774e..c4d0c2d 100644
--- a/test/Sema/block-misc.c
+++ b/test/Sema/block-misc.c
@@ -30,7 +30,7 @@
int test2(double (^S)()) {
double (^I)(int) = (void*) S;
- (void*)I = (void *)S; // expected-error {{expression is not assignable}}
+ (void*)I = (void *)S; // expected-error {{assignment to cast is illegal, lvalue casts are not supported}}
void *pv = I;
diff --git a/test/Sema/exprs.c b/test/Sema/exprs.c
index c98a7ed..8c8adc6 100644
--- a/test/Sema/exprs.c
+++ b/test/Sema/exprs.c
@@ -24,3 +24,8 @@
var = -5;
}
+// rdar://6319320
+void test5(int *X, float *P) {
+ (float*)X = P; // expected-error {{assignment to cast is illegal, lvalue casts are not supported}}
+}
+