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re PR c++/89785 (Incorrect "not a constant expression" error with switch statement that returns) 

PR c++/89785
	* constexpr.c (struct check_for_return_continue_data): New type.
	(check_for_return_continue): New function.
	(potential_constant_expression_1) <case SWITCH_STMT>: Walk
	SWITCH_STMT_BODY to find RETURN_EXPRs or CONTINUE_STMTs not nested
	in loop bodies and set *jump_target to that if found.

	* g++.dg/cpp1y/constexpr-89785-1.C: New test.
	* g++.dg/cpp1y/constexpr-89785-2.C: New test.

From-SVN: r269995
This commit is contained in:
Jakub Jelinek 2019-03-28 15:47:47 +01:00 committed by Jakub Jelinek
parent 12b9247b19
commit c7a53bdbb1
5 changed files with 185 additions and 1 deletions
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9
gcc/cp/ChangeLog
View File

@ -1,3 +1,12 @@
2019-03-28 Jakub Jelinek <jakub@redhat.com>
PR c++/89785
* constexpr.c (struct check_for_return_continue_data): New type.
(check_for_return_continue): New function.
(potential_constant_expression_1) <case SWITCH_STMT>: Walk
SWITCH_STMT_BODY to find RETURN_EXPRs or CONTINUE_STMTs not nested
in loop bodies and set *jump_target to that if found.
2019-03-27 Jason Merrill <jason@redhat.com>
PR c++/89831 - error with qualified-id in const member function.

99
gcc/cp/constexpr.c
View File

@ -5731,6 +5731,86 @@ check_automatic_or_tls (tree ref)
}
#endif
/* Data structure for passing data from potential_constant_expression_1
to check_for_return_continue via cp_walk_tree. */
struct check_for_return_continue_data {
hash_set<tree> *pset;
tree continue_stmt;
};
/* Helper function for potential_constant_expression_1 SWITCH_STMT handling,
called through cp_walk_tree. Return the first RETURN_EXPR found, or note
the first CONTINUE_STMT if RETURN_EXPR is not found. */
static tree
check_for_return_continue (tree *tp, int *walk_subtrees, void *data)
{
tree t = *tp, s;
check_for_return_continue_data *d = (check_for_return_continue_data *) data;
switch (TREE_CODE (t))
{
case RETURN_EXPR:
return t;
case CONTINUE_STMT:
if (d->continue_stmt == NULL_TREE)
d->continue_stmt = t;
break;
#define RECUR(x) \
if (tree r = cp_walk_tree (&x, check_for_return_continue, data, \
d->pset)) \
return r
/* For loops, walk subtrees manually, so that continue stmts found
inside of the bodies of the loops are ignored. */
case DO_STMT:
*walk_subtrees = 0;
RECUR (DO_COND (t));
s = d->continue_stmt;
RECUR (DO_BODY (t));
d->continue_stmt = s;
break;
case WHILE_STMT:
*walk_subtrees = 0;
RECUR (WHILE_COND (t));
s = d->continue_stmt;
RECUR (WHILE_BODY (t));
d->continue_stmt = s;
break;
case FOR_STMT:
*walk_subtrees = 0;
RECUR (FOR_INIT_STMT (t));
RECUR (FOR_COND (t));
RECUR (FOR_EXPR (t));
s = d->continue_stmt;
RECUR (FOR_BODY (t));
d->continue_stmt = s;
break;
case RANGE_FOR_STMT:
*walk_subtrees = 0;
RECUR (RANGE_FOR_EXPR (t));
s = d->continue_stmt;
RECUR (RANGE_FOR_BODY (t));
d->continue_stmt = s;
break;
#undef RECUR
case STATEMENT_LIST:
case CONSTRUCTOR:
break;
default:
if (!EXPR_P (t))
*walk_subtrees = 0;
break;
}
return NULL_TREE;
}
/* Return true if T denotes a potentially constant expression. Issue
diagnostic as appropriate under control of FLAGS. If WANT_RVAL is true,
an lvalue-rvalue conversion is implied. If NOW is true, we want to
@ -6196,7 +6276,24 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
if (!RECUR (SWITCH_STMT_COND (t), rval))
return false;
/* FIXME we don't check SWITCH_STMT_BODY currently, because even
unreachable labels would be checked. */
unreachable labels would be checked and it is enough if there is
a single switch cond value for which it is a valid constant
expression. We need to check if there are any RETURN_EXPRs
or CONTINUE_STMTs inside of the body though, as in that case
we need to set *jump_target. */
else
{
hash_set<tree> pset;
check_for_return_continue_data data = { &pset, NULL_TREE };
if (tree ret_expr
= cp_walk_tree (&SWITCH_STMT_BODY (t), check_for_return_continue,
&data, &pset))
/* The switch might return. */
*jump_target = ret_expr;
else if (data.continue_stmt)
/* The switch can't return, but might continue. */
*jump_target = data.continue_stmt;
}
return true;
case STMT_EXPR:

6
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,9 @@
2019-03-28 Jakub Jelinek <jakub@redhat.com>
PR c++/89785
* g++.dg/cpp1y/constexpr-89785-1.C: New test.
* g++.dg/cpp1y/constexpr-89785-2.C: New test.
2019-03-27 Janus Weil <janus@gcc.gnu.org>
PR fortran/85537

36
gcc/testsuite/g++.dg/cpp1y/constexpr-89785-1.C Normal file
View File

@ -0,0 +1,36 @@
// PR c++/89785
// { dg-do compile { target c++14 } }
constexpr int
foo (int x)
{
switch (x)
{
case 0:
throw -42;
case 2:
return 42;
}
throw 42;
}
constexpr int
bar (int x)
{
do
{
switch (x)
{
case 0:
throw 42;
case 1:
continue;
}
throw -42;
}
while (0);
return x;
}
static_assert (foo (2) == 42, "");
static_assert (bar (1) == 1, "");

36
gcc/testsuite/g++.dg/cpp1y/constexpr-89785-2.C Normal file
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@ -0,0 +1,36 @@
// PR c++/89785
// { dg-do compile { target c++14 } }
constexpr int
foo (int x)
{
switch (x)
{
case 0:
break;
case 2:
break;
}
throw 42; // { dg-error "is not a constant expression" }
return 0;
}
constexpr int
bar (int x)
{
do
{
switch (x)
{
case 0:
throw 42;
case 1:
for (int i = 0; i < 10; i++)
continue;
break;
}
throw -42; // { dg-error "is not a constant expression" }
}
while (0);
return x;
}