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| author | Jakub Jelinek <jakub@redhat.com> | 2022-10-24 16:25:29 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2022-10-24 16:25:29 +0200 |
| commit | da8c362c4c18cff2f2dfd5c4706bdda7576899a4 (patch) | |
| tree | 857d803ae8539362c83a411ab9736641454b9776 | |
| parent | f44575cb88727193386428e9ced3439e4f98f493 (diff) | |
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c++: Fix up constexpr handling of char/signed char/short pre/post inc/decrement [PR105774]
signed char, char or short int pre/post inc/decrement are represented by
normal {PRE,POST}_{INC,DEC}REMENT_EXPRs in the FE and only gimplification
ensures that the {PLUS,MINUS}_EXPR is done in unsigned version of those
types:
case PREINCREMENT_EXPR:
case PREDECREMENT_EXPR:
case POSTINCREMENT_EXPR:
case POSTDECREMENT_EXPR:
{
tree type = TREE_TYPE (TREE_OPERAND (*expr_p, 0));
if (INTEGRAL_TYPE_P (type) && c_promoting_integer_type_p (type))
{
if (!TYPE_OVERFLOW_WRAPS (type))
type = unsigned_type_for (type);
return gimplify_self_mod_expr (expr_p, pre_p, post_p, 1, type);
}
break;
}
This means during constant evaluation we need to do it similarly (either
using unsigned_type_for or using widening to integer_type_node).
The following patch does the latter.
2022-10-24 Jakub Jelinek <jakub@redhat.com>
PR c++/105774
* constexpr.cc (cxx_eval_increment_expression): For signed types
that promote to int, evaluate PLUS_EXPR or MINUS_EXPR in int type.
* g++.dg/cpp1y/constexpr-105774.C: New test.
| -rw-r--r-- | gcc/cp/constexpr.cc | 12 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp1y/constexpr-105774.C | 15 |
2 files changed, 27 insertions, 0 deletions
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index c3ee970..94b54fc 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -6234,6 +6234,18 @@ cxx_eval_increment_expression (const constexpr_ctx *ctx, tree t, offset = fold_build1 (NEGATE_EXPR, TREE_TYPE (offset), offset); mod = fold_build2 (POINTER_PLUS_EXPR, type, val, offset); } + else if (c_promoting_integer_type_p (type) + && !TYPE_UNSIGNED (type) + && TYPE_PRECISION (type) < TYPE_PRECISION (integer_type_node)) + { + offset = fold_convert (integer_type_node, offset); + mod = fold_convert (integer_type_node, val); + tree t = fold_build2 (inc ? PLUS_EXPR : MINUS_EXPR, integer_type_node, + mod, offset); + mod = fold_convert (type, t); + if (TREE_OVERFLOW_P (mod) && !TREE_OVERFLOW_P (t)) + TREE_OVERFLOW (mod) = false; + } else mod = fold_build2 (inc ? PLUS_EXPR : MINUS_EXPR, type, val, offset); if (!ptr) diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-105774.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-105774.C new file mode 100644 index 0000000..8ca6fce --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-105774.C @@ -0,0 +1,15 @@ +// PR c++/105774 +// { dg-do compile { target c++14 } } + +constexpr signed char +foo () +{ +#if __SCHAR_MAX__ < __INT_MAX__ + signed char x = __SCHAR_MAX__; +#else + signed char x = 0; +#endif + return ++x; +} + +constexpr auto a = foo (); |