Ok.
On Tue, Apr 17, 2018, 10:28 AM Jakub Jelinek <ja...@redhat.com> wrote:
> On Mon, Apr 16, 2018 at 10:55:34PM +0000, Jason Merrill wrote:
> > On Mon, Apr 16, 2018, 1:31 PM Jakub Jelinek <ja...@redhat.com> wrote:
> >
> > > On Mon, Apr 16, 2018 at 09:28:43PM +0200, Jakub Jelinek wrote:
> > > > On the following new testcase we emit 2 different constexpr errors
> > > > because of premature folding, where the PR44100 hack which is
> supposed
> > > > to fold expressions like &((S *)0)->f or
> > > > &((S *)24)->f folds all the &x->y expressions if x is TREE_CONSTANT
> > > > into (some type)(x + cst) where what we were actually trying to
> access
> > > > is lost.
> > > >
> > > > The following patch limits the offsetof-like expression hack to
> > > expressions
> > > > where maybe_constant_value of val's operand is INTEGER_CST, or e.g.
> > > > a cast of INTEGER_CST to some pointer type. This way we don't
> regress
> > > > e.g. init/struct2.C, but don't mess up with x is e.g. some constexpr
> > > > variable initialized to address of something. Or should it avoid
> > > > maybe_constant_value and just handle the literal INTEGER_CST and cast
> > > > thereof? We wouldn't handle &((S *)(24 + 8))->f that way though...
> > >
> > > Or shall we move this folding to cp_fold instead of
> cp_build_addr_expr_1
> > > (while keeping it limited to INTEGER_CST pointers)?
> >
> >
> > Yes, I think that would be better.
>
> Ok, here is a patch that does that. Compared to previous patch, the -O1
> for
> constexpr-nullptr-1.C is still needed, there is different diagnostics
> (dereference of null) in constexpr-nullptr-2.C on two lines and two lines
> that were commented due to this hack can now be handled. Similarly,
> array-size2.C XPASSes now, so removed the xfail in there.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-04-17 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/84463
> * typeck.c (cp_build_addr_expr_1): Move handling of offsetof-like
> tricks from here to ...
> * cp-gimplify.c (cp_fold) <case ADDR_EXPR>: ... here. Only use it
> if INDIRECT_REF's operand is INTEGER_CST cast to pointer type.
>
> * g++.dg/cpp0x/constexpr-nullptr-1.C: Add -O1 to dg-options.
> * g++.dg/cpp0x/constexpr-nullptr-2.C: Expect different diagnostics
> in two cases. Uncomment two other tests and add expected dg-error
> for
> them.
> * g++.dg/init/struct2.C: Cast to int rather than long to avoid
> -Wnarrowing diagnostics on some targets for c++11.
> * g++.dg/parse/array-size2.C: Remove xfail.
> * g++.dg/cpp0x/constexpr-84463.C: New test.
>
> --- gcc/cp/typeck.c.jj 2018-04-17 11:09:13.887127384 +0200
> +++ gcc/cp/typeck.c 2018-04-17 18:00:17.616039746 +0200
> @@ -5893,19 +5893,6 @@ cp_build_addr_expr_1 (tree arg, bool str
> return arg;
> }
>
> - /* ??? Cope with user tricks that amount to offsetof. */
> - if (TREE_CODE (argtype) != FUNCTION_TYPE
> - && TREE_CODE (argtype) != METHOD_TYPE
> - && argtype != unknown_type_node
> - && (val = get_base_address (arg))
> - && COMPLETE_TYPE_P (TREE_TYPE (val))
> - && INDIRECT_REF_P (val)
> - && TREE_CONSTANT (TREE_OPERAND (val, 0)))
> - {
> - tree type = build_pointer_type (argtype);
> - return fold_convert (type, fold_offsetof_1 (arg));
> - }
> -
> /* Handle complex lvalues (when permitted)
> by reduction to simpler cases. */
> val = unary_complex_lvalue (ADDR_EXPR, arg);
> --- gcc/cp/cp-gimplify.c.jj 2018-04-17 11:09:13.886127383 +0200
> +++ gcc/cp/cp-gimplify.c 2018-04-17 18:00:17.626039748 +0200
> @@ -2215,6 +2215,28 @@ cp_fold (tree x)
> goto unary;
>
> case ADDR_EXPR:
> + loc = EXPR_LOCATION (x);
> + op0 = cp_fold_maybe_rvalue (TREE_OPERAND (x, 0), false);
> +
> + /* Cope with user tricks that amount to offsetof. */
> + if (op0 != error_mark_node
> + && TREE_CODE (TREE_TYPE (op0)) != FUNCTION_TYPE
> + && TREE_CODE (TREE_TYPE (op0)) != METHOD_TYPE)
> + {
> + tree val = get_base_address (op0);
> + if (val
> + && INDIRECT_REF_P (val)
> + && COMPLETE_TYPE_P (TREE_TYPE (val))
> + && TREE_CONSTANT (TREE_OPERAND (val, 0)))
> + {
> + val = TREE_OPERAND (val, 0);
> + STRIP_NOPS (val);
> + if (TREE_CODE (val) == INTEGER_CST)
> + return fold_convert (TREE_TYPE (x), fold_offsetof_1 (op0));
> + }
> + }
> + goto finish_unary;
> +
> case REALPART_EXPR:
> case IMAGPART_EXPR:
> rval_ops = false;
> @@ -2232,6 +2254,7 @@ cp_fold (tree x)
> loc = EXPR_LOCATION (x);
> op0 = cp_fold_maybe_rvalue (TREE_OPERAND (x, 0), rval_ops);
>
> + finish_unary:
> if (op0 != TREE_OPERAND (x, 0))
> {
> if (op0 == error_mark_node)
> --- gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-1.C.jj 2018-04-17
> 11:09:13.697127292 +0200
> +++ gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-1.C 2018-04-17
> 18:00:17.705039771 +0200
> @@ -6,7 +6,7 @@
> // c++/67376 on gcc-patches for additional background.
>
> // { dg-do compile { target c++11 } }
> -// { dg-options "-fdelete-null-pointer-checks -fdump-tree-optimized" }
> +// { dg-options "-O1 -fdelete-null-pointer-checks -fdump-tree-optimized" }
>
> // Runtime assert. Used for potentially invalid expressions.
> #define RA(e) ((e) ? (void)0 : __builtin_abort ())
> --- gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-2.C.jj 2016-08-06
> 12:11:30.933757938 +0200
> +++ gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-2.C 2018-04-17
> 18:12:41.445247860 +0200
> @@ -192,12 +192,11 @@ constexpr bool b11 = ps >= (S*)0;
> constexpr S* ps1 = ps;
> constexpr S* ps2 = ps1;
>
> -// The following aren't diagnosed due to a bug.
> -// constexpr int* pi0 = &((S*)0)->i;
> -// constexpr int* pi1 = &((S*)nullptr)->i;
> +constexpr int* pi0 = &((S*)0)->i; // { dg-error "null pointer|not a
> constant" }
> +constexpr int* pi1 = &((S*)nullptr)->i; // { dg-error "null
> pointer|not a constant" }
>
> -constexpr int* pj0 = &((S*)0)->j; // { dg-error "not a constant
> expression" }
> -constexpr int* pj1 = &((S*)nullptr)->j; // { dg-error "not a constant
> expression" }
> +constexpr int* pj0 = &((S*)0)->j; // { dg-error "null pointer|not a
> constant" }
> +constexpr int* pj1 = &((S*)nullptr)->j; // { dg-error "null
> pointer|not a constant" }
>
> constexpr int* psi = &ps->i; // { dg-error "null pointer|not a
> constant" }
> constexpr int* psj = &ps->j; // { dg-error "null pointer|not a
> constant" }
> --- gcc/testsuite/g++.dg/init/struct2.C.jj 2018-04-17
> 11:09:13.746127314 +0200
> +++ gcc/testsuite/g++.dg/init/struct2.C 2018-04-17 18:00:17.750039783 +0200
> @@ -15,7 +15,7 @@ void saveOrLoad() {
> };
>
> SaveLoadEntry trackEntries = {
> - ((long) (__SIZE_TYPE__) (&((Track *) 42)->soundName[0])) - 42,
> + ((int) (__SIZE_TYPE__) (&((Track *) 42)->soundName[0])) - 42,
> 0, 1
> };
> saveLoadEntries(&trackEntries);
> --- gcc/testsuite/g++.dg/parse/array-size2.C.jj 2018-04-17
> 11:09:13.693127290 +0200
> +++ gcc/testsuite/g++.dg/parse/array-size2.C 2018-04-17
> 18:00:17.798039797 +0200
> @@ -15,6 +15,6 @@ void
> foo (void)
> {
> char g[(char *) &((struct S *) 0)->b - (char *) 0]; // { dg-error
> "constant" }
> - char h[(__SIZE_TYPE__) &((struct S *) 8)->b]; // {
> dg-error "constant" "" { xfail *-*-* } }
> + char h[(__SIZE_TYPE__) &((struct S *) 8)->b]; // {
> dg-error "constant" }
> bar (g, h);
> }
> --- gcc/testsuite/g++.dg/cpp0x/constexpr-84463.C.jj 2018-04-17
> 18:00:17.799039797 +0200
> +++ gcc/testsuite/g++.dg/cpp0x/constexpr-84463.C 2018-04-17
> 18:00:17.799039797 +0200
> @@ -0,0 +1,22 @@
> +// PR c++/84463
> +// { dg-do compile { target c++11 } }
> +
> +struct S { int r; const unsigned char s[5]; };
> +static constexpr S a[] = { { 0, "abcd" } };
> +struct T { const unsigned char s[5]; };
> +static constexpr T b[] = { { "abcd" } };
> +
> +constexpr int
> +foo (const unsigned char *x)
> +{
> + return x[0];
> +}
> +
> +constexpr static const S *j = &a[0];
> +constexpr static const int k = j->s[0];
> +constexpr static int l = foo (a[0].s);
> +constexpr static int m = foo (j->s);
> +constexpr static const T *n = &b[0];
> +constexpr static const int o = n->s[0];
> +constexpr static int p = foo (b[0].s);
> +constexpr static int q = foo (n->s);
>
>
> Jakub
>
