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da769814b8
Before GCC 8 C code like
const unsigned long long int neg = (const unsigned long long) -1;
void f(void) { static const double x = (neg); }
would get an error "initializer element is not constant". In GCC 8 and
later it does not.
Because a value like neg, above, can not be used as a general integer
constant, this causes cgo to conclude that it is a floating point
constant. The way that cgo handles floating point values then causes
it to get the wrong value for it: 18446744073709551615 rather than -1.
These are of course the same value when converted to int64, but Go
does not permit that kind of conversion for an out-of-range constant.
This CL side-steps the problem by treating floating point constants
with integer type as they would up being treated before GCC 8: as
variables rather than constants.
Fixes #26066
Change-Id: I6f2f9ac2fa8a4b8218481b474f0b539758eb3b79
Reviewed-on: https://go-review.googlesource.com/121035
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
20 lines
444 B
Go
20 lines
444 B
Go
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Wrong type of constant with GCC 8 and newer.
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package cgotest
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// const unsigned long long int issue26066 = (const unsigned long long) -1;
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import "C"
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import "testing"
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func test26066(t *testing.T) {
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var i = int64(C.issue26066)
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if i != -1 {
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t.Errorf("got %d, want -1", i)
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}
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}
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