The GNU C++ Library Manual
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The GNU C++ Library Manual

Paolo Carlini

Phil Edwards

Doug Gregor

Benjamin Kosnik

Dhruv Matani

Jason Merrill

Mark Mitchell

Nathan Myers

Felix Natter

Stefan Olsson

Johannes Singler

Ami Tavory

Jonathan Wakely

Table of Contents

I. Introduction

1. Status

Implementation Status

C++ 1998/2003

Implementation Status
Implementation Specific Behavior

C++ 2011

Implementation Specific Behavior

C++ 2014

Implementation Specific Behavior

Filesystem TS

C++ 2017

Implementation Specific Behavior

Parallelism 2 TS

C++ 2020

C++ TR1

Implementation Specific Behavior

C++ TR 24733

C++ IS 29124

Implementation Specific Behavior

License

The Code: GPL
The Documentation: GPL, FDL

Bugs

Implementation Bugs
Standard Bugs

2. Setup

Prerequisites
Configure
Make

3. Using

Command Options

Headers

Header Files
Mixing Headers
The C Headers and namespace std
Precompiled Headers

Macros

Dual ABI

Troubleshooting

Namespaces

Available Namespaces
namespace std
Using Namespace Composition

Linking

Almost Nothing
Finding Dynamic or Shared Libraries
Experimental Library Extensions

Structure
Defaults
Future
Alternatives

Containers

Exceptions

Exception Safety

Exception Neutrality

Doing without

Compatibility

With C
With POSIX thread cancellation

Debugging Support

Using g++

Debug Versions of Library Binary Files

Memory Leak Hunting

Non-memory leaks in Pool and MT allocators

Data Race Hunting

Using gdb

Tracking uncaught exceptions

Debug Mode

Compile Time Checking

II. Standard Contents

4. Support

Types

Fundamental Types
Numeric Properties
NULL

Dynamic Memory

Additional Notes

Termination

Termination Handlers
Verbose Terminate Handler

5. Diagnostics

Exceptions

API Reference
Adding Data to exception

Use of errno by the library

Interface Design
Selecting Default Allocation Policy
Disabling Memory Caching

Using a Specific Allocator

Custom Allocators

Extension Allocators

auto_ptr

Limitations
Use in Containers

Class Hierarchy
Thread Safety
Selecting Lock Policy
Related functions and classes

Use

Examples
Unresolved Issues

Simple Transformations
Case Sensitivity
Arbitrary Character Types
Tokenizing
Shrink to Fit
CString (MFC)

Interacting with "C" locales

Specializations

wchar_t Size
Support for Unicode
Other Issues

Models
The GNU Model

list::size() is O(n)

Associative

Insertion Hints

bitset

Size Variable
Type String

Unordered Associative

Insertion Hints

Hash Code

Hash Code Caching Policy

Interacting with C

Containers vs. Arrays

10. Iterators

Predefined

Iterators vs. Pointers
One Past the End

11. Algorithms

Mutating

swap

Specializations

12. Numerics

Complex

complex Processing

Generalized Operations

Interacting with C

Numerics vs. Arrays
C99

13. Input and Output

Iostream Objects

Stream Buffers

Derived streambuf Classes
Buffering

Memory Based Streams

Compatibility With strstream

File Based Streams

Copying a File
Binary Input and Output

Interacting with C

Using FILE* and file descriptors
Performance

14. Atomics

API Reference

15. Concurrency

API Reference

III. Extensions

16. Compile Time Checks

Using the Debug Mode
Using a Specific Debug Container

Design

Goals

Methods

The Wrapper Model

Safe Iterators
Safe Sequences (Containers)

Precondition Checking

Release- and debug-mode coexistence

Compile-time coexistence of release- and debug-mode components
Link- and run-time coexistence of release- and debug-mode components
Alternatives for Coexistence

Other Implementations

18. Parallel Mode

Intro

Semantics

Using

Prerequisite Compiler Flags
Using Parallel Mode
Using Specific Parallel Components

Design

Interface Basics

Configuration and Tuning

Setting up the OpenMP Environment
Compile Time Switches
Run Time Settings and Defaults

Implementation Namespaces

Testing

Bibliography

19. The mt_allocator

Intro

Design Issues

Overview

Implementation

Tunable Parameters
Initialization
Deallocation Notes

Single Thread Example

Multiple Thread Example

20. The bitmap_allocator

Super Block Data Layout

Maximum Wasted Percentage

allocate

deallocate

Questions

1
2
3

Locality

Overhead and Grow Policy

21. Policy-Based Data Structures

Intro

Performance Issues

Associative
Priority Que

Goals

Associative

Policy Choices
Underlying Data Structures
Iterators
Functional

Priority Queues

Policy Choices
Underlying Data Structures
Binary Heaps

Basic Use
Configuring via Template Parameters
Querying Container Attributes
Point and Range Iteration

Examples

Intermediate Use

Querying with container_traits

By Container Method

Hash-Based
Branch-Based
Priority Queues

Design

Concepts

Null Policy Classes

Map and Set Semantics

Distinguishing Between Maps and Sets
Alternatives to std::multiset and std::multimap

Iterator Semantics

Point and Range Iterators
Distinguishing Point and Range Iterators
Invalidation Guarantees

Genericity

Tag
Traits

By Container

hash

Interface
Details

tree

Interface
Details

Trie

Interface
Details

List

Interface
Details

Priority Queue

Interface
Details

Text find
Integer find
Integer Subscript find
Integer Subscript insert
Integer find with Skewed-Distribution
Erase Memory Use

Branch-Based

Text insert
Text find
Text find with Locality-of-Reference
split and join
Order-Statistics

Multimap

Text find with Small Secondary-to-Primary Key Ratios
Text find with Large Secondary-to-Primary Key Ratios
Text insert with Small Secondary-to-Primary Key Ratios
Text insert with Small Secondary-to-Primary Key Ratios
Text insert with Small Secondary-to-Primary Key Ratios Memory Use
Text insert with Small Secondary-to-Primary Key Ratios Memory Use

Priority Queue

Text push
Text push and pop
Integer push
Integer push
Text pop Memory Use
Text join
Text modify Up
Text modify Down

Observations

Associative
Priority_Queue

Acknowledgments

Bibliography

22. HP/SGI Extensions

Backwards Compatibility
Deprecated

27. Input and Output

Derived filebufs

28. Demangling

29. Concurrency

Design

Interface to Locks and Mutexes
Interface to Atomic Functions

Implementation

Using Built-in Atomic Functions
Thread Abstraction

Use

IV. Appendices

A. Contributing

Contributor Checklist

Reading
Assignment
Getting Sources
Submitting Patches

Directory Layout and Source Conventions

Coding Style

Bad Identifiers
By Example

Design Notes

B. Porting and Maintenance

Configure and Build Hacking

Prerequisites

Overview

General Process
What Comes from Where

Configure

Storing Information in non-AC files (like configure.host)
Coding and Commenting Conventions
The acinclude.m4 layout
GLIBCXX_ENABLE, the --enable maker
Shared Library Versioning

Make

Writing and Generating Documentation

Introduction

Generating Documentation

Doxygen

Prerequisites
Generating the Doxygen Files
Debugging Generation
Markup

Docbook

Prerequisites
Generating the DocBook Files
Debugging Generation
Editing and Validation
File Organization and Basics
Markup By Example

Porting to New Hardware or Operating Systems

Operating System
CPU
Character Types
Thread Safety
Numeric Limits
Libtool

Testing

Test Organization

Directory Layout
Naming Conventions

Running the Testsuite

Basic
Variations
Permutations

Writing a new test case

Examples of Test Directives
Directives Specific to Libstdc++ Tests

Test Harness and Utilities

DejaGnu Harness Details
Utilities

Special Topics

Qualifying Exception Safety Guarantees

Overview
Existing tests
C++11 Requirements Test Sequence Descriptions

ABI Policy and Guidelines

The C++ Interface

Versioning

Goals
History
Prerequisites
Configuring
Checking Active

Allowed Changes

Prohibited Changes

Implementation

Testing

Single ABI Testing
Multiple ABI Testing

Outstanding Issues

API Evolution and Deprecation History

5.3

6

7

7.2
7.3

Backwards Compatibility

First

Second

Third

Pre-ISO headers removed
Extension headers hash_map, hash_set moved to ext or backwards
No ios::nocreate/ios::noreplace.
No stream::attach(int fd)
Support for C++98 dialect.
Support for C++TR1 dialect.
Support for C++11 dialect.
Container::iterator_type is not necessarily Container::value_type*

C. Free Software Needs Free Documentation

D. GNU General Public License version 3

E. GNU Free Documentation License

List of Figures

21.1. Node Invariants
21.2. Underlying Associative Data Structures
21.3. Range Iteration in Different Data Structures
21.4. Point Iteration in Hash Data Structures
21.5. Effect of erase in different underlying data structures
21.6. Underlying Priority Queue Data Structures
21.7. Exception Hierarchy
21.8. Non-unique Mapping Standard Containers
21.9. Effect of embedded lists in std::multimap
21.10. Non-unique Mapping Containers
21.11. Point Iterator Hierarchy
21.12. Invalidation Guarantee Tags Hierarchy
21.13. Container Tag Hierarchy
21.14. Hash functions, ranged-hash functions, and range-hashing functions
21.15. Insert hash sequence diagram
21.16. Insert hash sequence diagram with a null policy
21.17. Hash policy class diagram
21.18. Balls and bins
21.19. Insert resize sequence diagram
21.20. Standard resize policy trigger sequence diagram
21.21. Standard resize policy size sequence diagram
21.22. Tree node invariants
21.23. Tree node invalidation
21.24. A tree and its update policy
21.25. Restoring node invariants
21.26. Insert update sequence
21.27. Useless update path
21.28. A PATRICIA trie
21.29. A trie and its update policy
21.30. A simple list
21.31. The counter algorithm
21.32. Underlying Priority-Queue Data-Structures.
21.33. Priority-Queue Data-Structure Tags.
B.1. Configure and Build File Dependencies

List of Tables

1.1. C++ 1998/2003 Implementation Status
1.2. C++ 2011 Implementation Status
1.3. C++ 2014 Implementation Status
1.4. C++ Technical Specifications Implementation Status
1.5. C++ 2017 Library Features
1.6. C++ 2017 Implementation Status
1.7. C++ Technical Specifications Implementation Status
1.8. Support for Extended ABI Tags
1.9. C++ 2020 Library Features
1.10. C++ TR1 Implementation Status
1.11. C++ TR 24733 Implementation Status
1.12. C++ Special Functions Implementation Status
3.1. C++ Command Options
3.2. C++ 1998 Library Headers
3.3. C++ 1998 Library Headers for C Library Facilities
3.4. C++ 1998 Deprecated Library Header
3.5. C++ 2011 Library Headers
3.6. C++ 2011 Library Headers for C Library Facilities
3.7. C++ 2014 Library Header
3.8. C++ 2017 Library Headers
3.9. C++ 2020 Library Headers
3.10. C++ 2020 Obsolete Headers
3.11. File System TS Header
3.12. Library Fundamentals TS Headers
3.13. C++ TR 1 Library Headers
3.14. C++ TR 1 Library Headers for C Library Facilities
3.15. C++ TR 24733 Decimal Floating-Point Header
3.16. C++ ABI Headers
3.17. Extension Headers
3.18. Extension Debug Headers
3.19. Extension Parallel Headers
17.1. Debugging Containers
17.2. Debugging Containers C++11
18.1. Parallel Algorithms
20.1. Bitmap Allocator Memory Map
B.1. Doxygen Prerequisites
B.2. HTML to Doxygen Markup Comparison
B.3. Docbook Prerequisites
B.4. HTML to Docbook XML Markup Comparison
B.5. Docbook XML Element Use
B.6. Extension Allocators
B.7. Extension Allocators Continued

List of Equations

21.1. Ranged Hash Function
21.2. Range-Hashing, Division Method
21.3. Division via Prime Modulo
21.4. Division via Bit Mask
21.5. A Standard String Hash Function
21.6. Only k String DNA Hash
21.7. Probability of Probe Sequence of Length k
21.8. Probability Probe Sequence in Some Bin