On 03/14/2016 03:25 PM, Martin Sebor wrote:
The attached patch fixes the outstanding cases mentioned in comment
10 on bug c++/67376. While testing the fix I uncovered a number of
other related problems without which the test would have been
incomplete. They include:
PR c++/70170 - [6 regression] bogus not a constant expression error
comparing pointer to array to null
PR c++/70172 - incorrect reinterpret_cast from integer to pointer
error on invalid constexpr initialization
PR c++/60760 - arithmetic on null pointers should not be allowed
in constant expressions
In addition, I include a fix for the issue below that I also came
across while testing the patch and that makes root causing constexpr
problems due to out-of-bounds array subscripts easier:
PR c++/70228 - insufficient detail in diagnostics for a constexpr
out of bounds array subscript
In a discussion of bug 70170 between those CC'd Marek posted
a prototype patch for match.pd. While the patch seems to do
the right thing as far as the bug goes, like my own first attempt
at a fix in const-fold.c it caused a couple of regressions (in
pr21294.c and in pr44555.c). Since I'm not yet familiar enough
with match.pd, in the interest of time I solved those regressions
in const-fold.c rather than in match.pd.
Tested on x86_64.
Martin
gcc-67376.patch
PR c++/67376 - [5/6 regression] Comparison with pointer to past-the-end
of array fails inside constant expression
PR c++/70170 - [6 regression] bogus not a constant expression error comparing
pointer to array to null
PR c++/70172 - incorrect reinterpret_cast from integer to pointer error
on invalid constexpr initialization
PR c++/60760 - arithmetic on null pointers should not be allowed in constant
expressions
PR c++/70228 - insufficient detail in diagnostics for a constexpr out of bounds
array subscript
gcc/testsuite/ChangeLog:
2016-03-14 Martin Sebor<mse...@redhat.com>
PR c++/67376
PR c++/70170
PR c++/70172
PR c++/60760
PR c++/70228
* g++.dg/cpp0x/constexpr-array-ptr10.C: New test.
* g++.dg/cpp0x/constexpr-array-ptr11.C: New test.
* g++.dg/cpp0x/constexpr-array-ptr9.C: New test.
* g++.dg/cpp0x/constexpr-array5.C: Adjust text of expected diagnostic.
* g++.dg/cpp0x/constexpr-string.C: Same.
* g++.dg/cpp0x/constexpr-wstring2.C: Same.
* g++.dg/cpp0x/pr65398.C: Same.
* g++.dg/ext/constexpr-vla1.C: Same.
* g++.dg/ext/constexpr-vla2.C: Same.
* g++.dg/ext/constexpr-vla3.C: Same.
* g++.dg/ubsan/pr63956.C: Same.
gcc/cp/ChangeLog:
2016-03-14 Martin Sebor<mse...@redhat.com>
PR c++/67376
PR c++/70170
PR c++/70172
PR c++/60760
PR c++/70228
(cxx_eval_binary_expression): Add argument.
(cxx_eval_component_reference): Same.
(cxx_eval_constant_expression): Same.
(cxx_eval_indirect_ref): Same.
(cxx_eval_outermost_constant_expr): Same.
(diag_array_subscript): New function.
* constexpr.c (cxx_eval_call_expression): Adjust.
(cxx_eval_conditional_expression): Same.
(cxx_eval_array_reference): Detect null pointers.
(cxx_eval_statement_list): Adjust.
gcc/ChangeLog:
2016-03-14 Martin Sebor<mse...@redhat.com>
PR c++/67376
* fold-const.c (fold_comparison): Fold equality and relational
expressions involving null pointers.
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 5f97c9d..5ec5034 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -918,7 +918,8 @@ struct constexpr_ctx {
static GTY (()) hash_table<constexpr_call_hasher> *constexpr_call_table;
static tree cxx_eval_constant_expression (const constexpr_ctx *, tree,
- bool, bool *, bool *, tree * = NULL);
+ bool, bool *, bool *, bool * = NULL,
+ tree * = NULL);
I didn't look deeply, but do you end up fixing all (most) of the callers
of cxx_eval_constant_expression? If so, then you don't need the default
initialization.
At a high level, I'm curious your thoughts on emitting these errors out
of the front-end rather than after analysis. I'm thinking in particular
about constant propagation, unreachable code elimination and DCE. The
former can expose cases that are difficult to catch in the front-end,
while the latter two might remove an out-of-range comparison/reference.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 696b4a6..376aa09 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -8639,6 +8639,37 @@ fold_comparison (location_t loc, enum tree_code code,
tree type,
base1 = build_fold_addr_expr_loc (loc, base1);
return fold_build2_loc (loc, code, type, base0, base1);
}
+
+ /* Comparison between an ordinary (non-weak) symbol and a null
+ pointer can be eliminated since such sybols must have a non
+ null address. */
Hmm, I thought we already had code to do this somewhere. It looks like
it's moved around quite a bit. I think you want to be using
symtab_node::nonzero_address to determine if a given symbol must bind to
a nonzero address.
Jeff
