Author: Aaron Ballman Date: 2021-07-22T14:53:23-04:00 New Revision: 178c2b4c1eb12b2153adb384ac7f22a8791edc86
URL: https://github.com/llvm/llvm-project/commit/178c2b4c1eb12b2153adb384ac7f22a8791edc86 DIFF: https://github.com/llvm/llvm-project/commit/178c2b4c1eb12b2153adb384ac7f22a8791edc86.diff LOG: Correctly diagnose taking the address of a register variable in C We caught the cases where the user would explicitly use the & operator, but we were missing implicit conversions such as array decay. Fixes PR26336. Thanks to Samuel Neves for inspiration for the patch. Added: Modified: clang/lib/Sema/Sema.cpp clang/lib/Sema/SemaExpr.cpp clang/test/Sema/expr-address-of.c Removed: ################################################################################ diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp index fbbb347f57da..054a65265079 100644 --- a/clang/lib/Sema/Sema.cpp +++ b/clang/lib/Sema/Sema.cpp @@ -629,16 +629,36 @@ ExprResult Sema::ImpCastExprToType(Expr *E, QualType Ty, if (ExprTy == TypeTy) return E; - // C++1z [conv.array]: The temporary materialization conversion is applied. - // We also use this to fuel C++ DR1213, which applies to C++11 onwards. - if (Kind == CK_ArrayToPointerDecay && getLangOpts().CPlusPlus && - E->getValueKind() == VK_PRValue) { - // The temporary is an lvalue in C++98 and an xvalue otherwise. - ExprResult Materialized = CreateMaterializeTemporaryExpr( - E->getType(), E, !getLangOpts().CPlusPlus11); - if (Materialized.isInvalid()) - return ExprError(); - E = Materialized.get(); + if (Kind == CK_ArrayToPointerDecay) { + // C++1z [conv.array]: The temporary materialization conversion is applied. + // We also use this to fuel C++ DR1213, which applies to C++11 onwards. + if (getLangOpts().CPlusPlus && E->getValueKind() == VK_PRValue) { + // The temporary is an lvalue in C++98 and an xvalue otherwise. + ExprResult Materialized = CreateMaterializeTemporaryExpr( + E->getType(), E, !getLangOpts().CPlusPlus11); + if (Materialized.isInvalid()) + return ExprError(); + E = Materialized.get(); + } + // C17 6.7.1p6 footnote 124: The implementation can treat any register + // declaration simply as an auto declaration. However, whether or not + // addressable storage is actually used, the address of any part of an + // object declared with storage-class specifier register cannot be + // computed, either explicitly(by use of the unary & operator as discussed + // in 6.5.3.2) or implicitly(by converting an array name to a pointer as + // discussed in 6.3.2.1).Thus, the only operator that can be applied to an + // array declared with storage-class specifier register is sizeof. + if (VK == VK_PRValue && !getLangOpts().CPlusPlus && !E->isPRValue()) { + if (const auto *DRE = dyn_cast<DeclRefExpr>(E)) { + if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) { + if (VD->getStorageClass() == SC_Register) { + Diag(E->getExprLoc(), diag::err_typecheck_address_of) + << /*register variable*/ 3 << E->getSourceRange(); + return ExprError(); + } + } + } + } } if (ImplicitCastExpr *ImpCast = dyn_cast<ImplicitCastExpr>(E)) { diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index 3926c49077ce..d19eb8475e9f 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -525,9 +525,13 @@ ExprResult Sema::DefaultFunctionArrayConversion(Expr *E, bool Diagnose) { // An lvalue or rvalue of type "array of N T" or "array of unknown bound of // T" can be converted to an rvalue of type "pointer to T". // - if (getLangOpts().C99 || getLangOpts().CPlusPlus || E->isLValue()) - E = ImpCastExprToType(E, Context.getArrayDecayedType(Ty), - CK_ArrayToPointerDecay).get(); + if (getLangOpts().C99 || getLangOpts().CPlusPlus || E->isLValue()) { + ExprResult Res = ImpCastExprToType(E, Context.getArrayDecayedType(Ty), + CK_ArrayToPointerDecay); + if (Res.isInvalid()) + return ExprError(); + E = Res.get(); + } } return E; } diff --git a/clang/test/Sema/expr-address-of.c b/clang/test/Sema/expr-address-of.c index 480871afad2a..aed488284ab1 100644 --- a/clang/test/Sema/expr-address-of.c +++ b/clang/test/Sema/expr-address-of.c @@ -45,24 +45,27 @@ void f0() { int *_dummy1 = &(*(x1 + 1)); } -// FIXME: The checks for this function are broken; we should error -// on promoting a register array to a pointer! (C99 6.3.2.1p3) void f1() { register int x0[10]; - int *_dummy00 = x0; // fixme-error {{address of register variable requested}} - int *_dummy01 = &(*x0); // fixme-error {{address of register variable requested}} + int *_dummy00 = x0; // expected-error {{address of register variable requested}} + int *_dummy01 = &(*x0); // expected-error {{address of register variable requested}} register int x1[10]; - int *_dummy1 = &(*(x1 + 1)); // fixme-error {{address of register variable requested}} + int *_dummy1 = &(*(x1 + 1)); // expected-error {{address of register variable requested}} register int *x2; int *_dummy2 = &(*(x2 + 1)); register int x3[10][10][10]; - int (*_dummy3)[10] = &x3[0][0]; // expected-error {{address of register variable requested}} + int(*_dummy3)[10] = &x3[0][0]; // expected-error {{address of register variable requested}} register struct { int f0[10]; } x4; int *_dummy4 = &x4.f0[2]; // expected-error {{address of register variable requested}} + + add_one(x0); // expected-error {{address of register variable requested}} + (void)sizeof(x0); // OK, not an array decay. + + int *p = ((int *)x0)++; // expected-error {{address of register variable requested}} } void f2() { @@ -86,12 +89,8 @@ void f4() { void f5() { register int arr[2]; - /* This is just here because if we happened to support this as an - lvalue we would need to give a warning. Note that gcc warns about - this as a register before it warns about it as an invalid - lvalue. */ - int *_dummy0 = &(int*) arr; // expected-error {{cannot take the address of an rvalue}} - int *_dummy1 = &(arr + 1); // expected-error {{cannot take the address of an rvalue}} + int *_dummy0 = &(int*) arr; // expected-error {{address of register variable requested}} + int *_dummy1 = &(arr + 1); // expected-error {{address of register variable requested}} } void f6(register int x) { _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
