On Tue, 26 Feb 2019, Jakub Jelinek wrote:
> Hi!
>
> Seems valid_constant_size_p has been written with the expectation that only
> sizetype/ssizetype constants will be passed to it, otherwise it couldn't
> ever just blindly test tree_int_cst_sign_bit (size) for unsigned
> INTEGER_CSTs and complain cst_size_too_big.
> Unfortunately a recent patch started using this function even on other
> types, and the comment explicitly talk about it being done on
> pre-conversion to sizetype:
> /* The expression in a noptr-new-declarator is erroneous if it's of
> non-class type and its value before converting to std::size_t is
> less than zero. ... If the expression is a constant expression,
> the program is ill-fomed. */
> if (TREE_CODE (cst_nelts) == INTEGER_CST
> && !valid_array_size_p (input_location, cst_nelts, NULL_TREE,
> complain & tf_error))
> return error_mark_node;
> E.g. __int128 negative value could fit just fine after cast to sizetype,
> etc.
>
> So, instead of changing the C++ FE to only complain about negative cst_elts
> normally and fold_convert everything to sizetype before checking, this patch
> attempts to deal with non-{,s}sizetype constants. Negative (signed)
> constants are always rejected as before, newly constants that don't fit into
> uhwi are rejected after that check regardless of signedness and anything
> larger or equal than SIZE_MAX / 2 is also rejected as too big.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2019-02-26 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/89507
> * tree.c (valid_constant_size_p): Deal with size INTEGER_CSTs
> with types other than sizetype/ssizetype.
>
> * g++.dg/other/new2.C: New test.
>
> --- gcc/tree.c.jj 2019-02-18 20:48:35.745681423 +0100
> +++ gcc/tree.c 2019-02-26 18:22:23.760753681 +0100
> @@ -7533,19 +7533,16 @@ valid_constant_size_p (const_tree size,
> return false;
> }
>
> - tree type = TREE_TYPE (size);
> - if (TYPE_UNSIGNED (type))
> + if (tree_int_cst_sgn (size) < 0)
> {
> - if (!tree_fits_uhwi_p (size)
> - || tree_int_cst_sign_bit (size))
> - {
> - *perr = cst_size_too_big;
> - return false;
> - }
> + *perr = cst_size_negative;
> + return false;
> }
> - else if (tree_int_cst_sign_bit (size))
> + if (!tree_fits_uhwi_p (size)
> + || (wi::to_widest (TYPE_MAX_VALUE (sizetype))
> + < wi::to_widest (size) * 2))
> {
> - *perr = cst_size_negative;
> + *perr = cst_size_too_big;
> return false;
> }
>
> --- gcc/testsuite/g++.dg/other/new2.C.jj 2019-02-26 18:24:23.792785651
> +0100
> +++ gcc/testsuite/g++.dg/other/new2.C 2019-02-26 18:23:26.530724514 +0100
> @@ -0,0 +1,5 @@
> +// PR c++/89507
> +// { dg-do compile }
> +
> +unsigned char const n = 128;
> +int *p = new int[n]; // { dg-bogus "array exceeds maximum object size" }
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
