Hi!
The following patch adds some tweaks for -Wsequence-point warning for C++17
and later. In particular, stop warning about no sequence point in between
<<, >>, ., -> and [] expressions, where E1 is in C++17 sequenced before E2.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
As mentioned in the PR, this is just part of the needed changes, I've tried
to adjust handling of MODIFY_EXPR, but didn't figure out exactly what needs
to be done, and .* / ->* aren't handled either, and CALL_EXPR needs probably
some verification too.
2019-08-12 Jakub Jelinek <ja...@redhat.com>
PR c++/91415
* c-common.c (verify_tree): For LSHIFT_EXPR, RSHIFT_EXPR,
COMPONENT_REF and ARRAY_REF in cxx_dialect >= cxx17 mode handle it
like COMPOUND_EXPR rather than normal expression.
* g++.dg/warn/sequence-pt-4.C: New test.
--- gcc/c-family/c-common.c.jj 2019-08-12 09:45:54.463491950 +0200
+++ gcc/c-family/c-common.c 2019-08-12 12:01:32.783135654 +0200
@@ -1889,6 +1889,7 @@ verify_tree (tree x, struct tlist **pbef
case COMPOUND_EXPR:
case TRUTH_ANDIF_EXPR:
case TRUTH_ORIF_EXPR:
+ sequenced_binary:
tmp_before = tmp_nosp = tmp_list2 = tmp_list3 = 0;
verify_tree (TREE_OPERAND (x, 0), &tmp_before, &tmp_nosp, NULL_TREE);
warn_for_collisions (tmp_nosp);
@@ -2031,8 +2035,18 @@ verify_tree (tree x, struct tlist **pbef
x = TREE_OPERAND (x, 0);
goto restart;
}
- gcc_fallthrough ();
+ goto do_default;
+
+ case LSHIFT_EXPR:
+ case RSHIFT_EXPR:
+ case COMPONENT_REF:
+ case ARRAY_REF:
+ if (cxx_dialect >= cxx17)
+ goto sequenced_binary;
+ goto do_default;
+
default:
+ do_default:
/* For other expressions, simply recurse on their operands.
Manual tail recursion for unary expressions.
Other non-expressions need not be processed. */
--- gcc/testsuite/g++.dg/warn/sequence-pt-4.C.jj 2019-08-12
12:16:27.205660149 +0200
+++ gcc/testsuite/g++.dg/warn/sequence-pt-4.C 2019-08-12 12:22:07.540530959
+0200
@@ -0,0 +1,21 @@
+/* More sequence point warning tests */
+/* { dg-do compile } */
+/* { dg-options "-Wsequence-point" } */
+
+struct S { int a[10]; };
+void bar (int, int, int, int, int, int, int, int);
+
+int
+foo (int i, int x[10][10], int y[10], struct S z[10], struct S *w[10])
+{
+ int b = x[i++][i++]; /* { dg-warning "undefined" "sequence point warning" {
target c++14_down } } */
+ int c = i++ << i++; /* { dg-warning "undefined" "sequence point warning" {
target c++14_down } } */
+ int d = i++ >> i++; /* { dg-warning "undefined" "sequence point warning" {
target c++14_down } } */
+ int e = i++ && i++;
+ int f = i++ ? i++ : i++;
+ int g = (i++, i++);
+ int h = z[i++].a[i++]; /* { dg-warning "undefined" "sequence point
warning" { target c++14_down } } */
+ int j = w[i++]->a[i++]; /* { dg-warning "undefined" "sequence point
warning" { target c++14_down } } */
+ bar (b, c, d, e, f,g, h, j);
+ return i;
+}
Jakub
