mirror of
https://github.com/open-telemetry/opentelemetry-go.git
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72 lines
2.2 KiB
Go
72 lines
2.2 KiB
Go
// Copyright The OpenTelemetry Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package internaltest
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/*
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This file contains common utilities and objects to validate memory alignment
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of Go types. The primary use of this functionality is intended to ensure
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`struct` fields that need to be 64-bit aligned so they can be passed as
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arguments to 64-bit atomic operations.
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The common workflow is to define a slice of `FieldOffset` and pass them to the
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`Aligned8Byte` function from within a `TestMain` function from a package's
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tests. It is important to make this call from the `TestMain` function prior
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to running the rest of the test suit as it can provide useful diagnostics
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about field alignment instead of ambiguous nil pointer dereference and runtime
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panic.
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For more information:
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https://github.com/open-telemetry/opentelemetry-go/issues/341
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*/
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import (
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"fmt"
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"io"
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)
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// FieldOffset is a preprocessor representation of a struct field alignment.
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type FieldOffset struct {
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// Name of the field.
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Name string
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// Offset of the field in bytes.
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//
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// To compute this at compile time use unsafe.Offsetof.
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Offset uintptr
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}
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// Aligned8Byte returns if all fields are aligned modulo 8-bytes.
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//
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// Error messaging is printed to out for any field determined misaligned.
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func Aligned8Byte(fields []FieldOffset, out io.Writer) bool {
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misaligned := make([]FieldOffset, 0)
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for _, f := range fields {
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if f.Offset%8 != 0 {
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misaligned = append(misaligned, f)
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}
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}
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if len(misaligned) == 0 {
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return true
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}
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fmt.Fprintln(out, "struct fields not aligned for 64-bit atomic operations:")
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for _, f := range misaligned {
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fmt.Fprintf(out, " %s: %d-byte offset\n", f.Name, f.Offset)
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}
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return false
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}
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