[cfe-commits] r59460 - in /cfe/trunk: include/clang/AST/Expr.h include/clang/Basic/DiagnosticKinds.def lib/AST/Expr.cpp lib/Sema/SemaExpr.cpp test/Sema/block-misc.c test/Sema/exprs.c

[Fariborz Jahanian]

We used to need this for objc'gc; as in:

% cat test.m
id p;

int main()
{
	(__strong id)p = 0;
}

But, having said that, I recently introduced warning for this kind of  
lvalue-casts in gcc:

% mygccpw -fobjc-gc -c test.m
test.m: In function 'main':
test.m:5: warning: target of assignment not really an lvalue; this  
will be a hard error in the future

And I have not heard of any project failures. So, it should be OK for  
clang.

- fariborz

On Nov 17, 2008, at 11:51 AM, Chris Lattner wrote:

> Author: lattner
> Date: Mon Nov 17 13:51:54 2008
> New Revision: 59460
>
> URL: http://llvm.org/viewvc/llvm-project?rev=59460&view=rev
> Log:
> 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.
>
>
>
> Modified:
>    cfe/trunk/include/clang/AST/Expr.h
>    cfe/trunk/include/clang/Basic/DiagnosticKinds.def
>    cfe/trunk/lib/AST/Expr.cpp
>    cfe/trunk/lib/Sema/SemaExpr.cpp
>    cfe/trunk/test/Sema/block-misc.c
>    cfe/trunk/test/Sema/exprs.c
>
> Modified: cfe/trunk/include/clang/AST/Expr.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Expr.h?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/include/clang/AST/Expr.h (original)
> +++ cfe/trunk/include/clang/AST/Expr.h Mon Nov 17 13:51:54 2008
> @@ -99,6 +99,7 @@
>     MLV_IncompleteVoidType,
>     MLV_DuplicateVectorComponents,
>     MLV_InvalidExpression,
> +    MLV_LValueCast,           // Specialized form of  
> MLV_InvalidExpression.
>     MLV_IncompleteType,
>     MLV_ConstQualified,
>     MLV_ArrayType,
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticKinds.def
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticKinds.def?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticKinds.def (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticKinds.def Mon Nov 17  
> 13:51:54 2008
> @@ -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)")
>
> Modified: cfe/trunk/lib/AST/Expr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/lib/AST/Expr.cpp (original)
> +++ cfe/trunk/lib/AST/Expr.cpp Mon Nov 17 13:51:54 2008
> @@ -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());
>
> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Mon Nov 17 13:51:54 2008
> @@ -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());
>
> Modified: cfe/trunk/test/Sema/block-misc.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/block-misc.c?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/test/Sema/block-misc.c (original)
> +++ cfe/trunk/test/Sema/block-misc.c Mon Nov 17 13:51:54 2008
> @@ -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;
>
>
> Modified: cfe/trunk/test/Sema/exprs.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/exprs.c?rev=59460&r1=59459&r2=59460&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/test/Sema/exprs.c (original)
> +++ cfe/trunk/test/Sema/exprs.c Mon Nov 17 13:51:54 2008
> @@ -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}}
> +}
> +
>
>
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