[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 Marek Polacek mpolacek at gcc dot gnu.org changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org --- Comment #5 from Marek Polacek mpolacek at gcc dot gnu.org --- Maybe best would be to remove the optimization in pointer_diff altogether. Mine for now.
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 --- Comment #6 from Jakub Jelinek jakub at gcc dot gnu.org --- But in that case we should have an adequate replacement on the match_and_simplify side.
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 --- Comment #7 from Marek Polacek mpolacek at gcc dot gnu.org --- But C++ has its own pointer_diff version that doesn't do such optimization. With my change the C FE would generate the same expr as the C++ FE. And FEs shouldn't perform such optimizations anyway.
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 Jakub Jelinek jakub at gcc dot gnu.org changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #4 from Jakub Jelinek jakub at gcc dot gnu.org --- Started with r184965.
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240
Marek Polacek mpolacek at gcc dot gnu.org changed:
What|Removed |Added
CC||mpolacek at gcc dot gnu.org
--- Comment #3 from Marek Polacek mpolacek at gcc dot gnu.org ---
Richi, did you mean something like this? With this we wouldn't warn on nor p -
(p - 1); neither q - (q - 1); line...
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -3513,6 +3513,9 @@ pointer_diff (location_t loc, tree op0, tree op1)
{
lit0 = TREE_OPERAND (con0, 1);
con0 = TREE_OPERAND (con0, 0);
+ lit0 = convert (inttype, lit0);
+ if (TREE_CODE (lit0) == INTEGER_CST)
+ TREE_OVERFLOW (lit0) = 0;
}
else
lit0 = integer_zero_node;
@@ -3521,6 +3524,9 @@ pointer_diff (location_t loc, tree op0, tree op1)
{
lit1 = TREE_OPERAND (con1, 1);
con1 = TREE_OPERAND (con1, 0);
+ lit1 = convert (inttype, lit1);
+ if (TREE_CODE (lit1) == INTEGER_CST)
+ TREE_OVERFLOW (lit1) = 0;
}
else
lit1 = integer_zero_node;
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 Richard Biener rguenth at gcc dot gnu.org changed: What|Removed |Added Target Milestone|4.8.3 |4.8.4 --- Comment #2 from Richard Biener rguenth at gcc dot gnu.org --- GCC 4.8.3 is being released, adjusting target milestone.
[Bug c/61240] [4.8/4.9/4.10 Regression] Incorrect warning integer overflow in expression on pointer-pointer subtraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240 Richard Biener rguenth at gcc dot gnu.org changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2014-05-20 Target Milestone|--- |4.8.3 Summary|Incorrect warning integer |[4.8/4.9/4.10 Regression] |overflow in expression on |Incorrect warning integer |pointer-pointer subtraction |overflow in expression on ||pointer-pointer subtraction Ever confirmed|0 |1 --- Comment #1 from Richard Biener rguenth at gcc dot gnu.org --- We warn for integer_cst 0x76d54e28 type integer_type 0x76c407e0 long int constant public overflow 1 via c-common.c:overflow_warning called from #1 0x0065b80e in parser_build_binary_op (location=5653, code=MINUS_EXPR, arg1=..., arg2=...) at /space/rguenther/src/svn/trunk/gcc/c/c-typeck.c:3411 #2 0x0068f5ed in c_parser_binary_expression (parser=0x76d67000, after=0x0, omp_atomic_lhs=tree 0x0) at /space/rguenther/src/svn/trunk/gcc/c/c-parser.c:6282 #3 0x0068dfee in c_parser_conditional_expression ( parser=0x76d67000, after=0x0, omp_atomic_lhs=tree 0x0) at /space/rguenther/src/svn/trunk/gcc/c/c-parser.c:5934 #4 0x0068dd75 in c_parser_expr_no_commas (parser=0x76d67000, after=0x0, omp_atomic_lhs=tree 0x0) at /space/rguenther/src/svn/trunk/gcc/c/c-parser.c:5852 when building p - (p + -1U) which gets simplified to - -1U - 1U (with overflow set - as it's sizetype arithmetic). pointer_diff is guilty here which calls /* First do the subtraction as integers; then drop through to build the divide operator. Do not do default conversions on the minus operator in case restype is a short type. */ op0 = build_binary_op (loc, MINUS_EXPR, convert (inttype, op0), convert (inttype, op1), 0); doing 0 - -1U, converting them to inttype (long int) first. I suggest to do that conversion and strip overflow bits in the POINTER_PLUS_EXPR decomposition part.
