《Oracle Solaris 9编程接口指南-260》

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Oracle Solaris 9 - Programming Interfaces Guide-260是一本由Sun Microsystems, Inc.出版的专业编程接口指南。该指南详细介绍了Oracle Solaris 9操作系统的编程接口，旨在帮助开发人员更好地理解和利用Solaris 9系统的编程功能。该指南的内容涵盖了各种编程接口的使用方法和技巧，包括系统调用、库函数、设备驱动程序等。通过阅读该指南，开发人员可以了解如何在Solaris 9系统中进行编程，以及如何利用系统提供的各种接口来实现功能和解决问题。此外，该指南还介绍了一些第三方软件和技术，以及其在Solaris 9系统中的使用和集成。通过学习这些内容，开发人员可以更好地利用第三方资源，为他们的应用程序增加更多的功能和特性。总的来说，Oracle Solaris 9 - Programming Interfaces Guide-260是一本非常实用的编程指南，对于想要深入了解和利用Solaris 9系统编程接口的开发人员来说，是一本不可或缺的参考书籍。

The ﬂags MAP_SHARED and MAP_PRIVATE specify the type of mapping. You must

specify a mapping type. If the MAP_SHARED ﬂag is set, write operations modify the

mapped object. No further operations on the object are needed to make the change. If

the MAP_PRIVATE ﬂag is set, the ﬁrst write operation to the mapped area creates a

copy of the page. All further write operations reference the copy. Only modiﬁed pages

are copied.

A mapping type is retained across a fork(2).

After you have established the mapping through mmap(2), the ﬁle descriptor used in

the call is no longer used. If you close the ﬁle, the mapping remains until munmap(2)

undoes the mapping. Creating a new mapping replaces an existing mapping.

A mapped ﬁle can be shortened by a call to truncate. An attempt to access the area of

the ﬁle that no longer exists causes a SIGBUS signal.

Mapping /dev/zero gives the calling program a block of zero-ﬁlled virtual memory.

The size of the block is speciﬁed in the call to mmap(2). The following code fragment

demonstrates a use of this technique to create a block of zeroed storage in a program.

The block’s address is chosen by the system.

removed to fr.ch4/pl1.create.mapping.c

Some devices or ﬁles are useful only when accessed by mapping. Frame buffer devices

used to support bit-mapped displays are an example of this phenomenon. Display

management algorithms are much simpler to implement when the algorithms operate

directly on the addresses of the display.

Removing Mappings

munmap(2) removes all mappings of pages in the speciﬁed address range of the calling

process. munmap(2) has no affect on the objects that were mapped.

Cache Control

The virtual memory system in SunOS is a cache system, in which processor memory

buffers data from ﬁle system objects. Interfaces are provided to control or interrogate

the status of the cache.

Using mincore

The mincore(2) interface determines the residency of the memory pages in the

address space covered by mappings in the speciﬁed range. Because the status of a

page can change after mincore checks the page but before mincore returns the data,

returned information can be outdated. Only locked pages are guaranteed to remain in

memory.

16 Programming Interfaces Guide • December 2003

Using mlock and munlock

mlock(3C) causes the pages in the speciﬁed address range to be locked in physical

memory. References to locked pages in this process or in other processes do not result

in page faults that require an I/O operation. Because this I/O operation interferes with

normal operation of virtual memory, as well as slowing other processes, the use of

mlock is limited to the superuser. The limit to the number of pages that can be locked

in memory is dependent on system conﬁguration. The call to mlock fails if this limit is

exceeded.

munlock releases the locks on physical pages. If multiple mlock calls are made on an

address range of a single mapping, a single munlock call releases the locks. However,

if different mappings to the same pages are locked by mlock, the pages are not

unlocked until the locks on all the mappings are released.

Removing a mapping also releases locks, either through being replaced with an

mmap(2) operation or removed with munmap(2).

The copy-on-write event that is associated with a MAP_PRIVATE mapping transfers a

lock on the source page to the destination page. Thus locks on an address range that

includes MAP_PRIVATE mappings are retained transparently along with the

copy-on-write redirection. For a discussion of this redirection, see “Creating and Using

Mappings” on page 15.

Using mlockall and munlockall

mlockall(3C) and munlockall(3C) are similar to mlock and munlock, but

mlockall and munlockall operate on entire address spaces. mlockall sets locks

on all pages in the address space and munlockall removes all locks on all pages in

the address space, whether established by mlock or mlockall.

Using msync

msync(3C) causes all modiﬁed pages in the speciﬁed address range to be ﬂushed to

the objects mapped by those addresses. This command is similar to fsync(3C), which

operates on ﬁles.

Library-Level Dynamic Memory

Library-level dynamic memory allocation provides an easy-to-use interface to

dynamic memory allocation.

Chapter 1 • Memory Management 17

Dynamic Memory Allocation

The most often used interfaces are:

■

malloc(3C)

■

free(3C)

■

calloc(3C)

■

cfree(3MALLOC)

Other dynamic memory allocation interfaces are memalign(3C), valloc(3C), and

realloc(3C)

■

malloc returns a pointer to a block of memory at least as large as the amount of

memory that is requested. The block is aligned to store any type of data.

■

free returns the memory that is obtained from malloc, calloc, realloc,

memalign,orvalloc to system memory. Trying to free a block that was not

reserved by a dynamic memory allocation interface is an error that can cause a

process to crash.

■

calloc returns a pointer to a block of memory that is initialized to zeros. Memory

reserved by calloc can be returned to the system through either cfree or free.

The memory is allocated and aligned to contain an array of a speciﬁed number of

elements of a speciﬁed size.

■

memalign allocates a speciﬁed number of bytes on a speciﬁed alignment

boundary. The alignment boundary must be a power of 2.

■

valloc allocates a speciﬁed number of bytes that are aligned on a page boundary.

■

realloc changes the size of the memory block allocated to a process. realloc

can be used to increase or reduce the size of an allocated block of memory.

realloc is the only way to shrink a memory allocation without causing a

problem. The location in memory of the reallocated block might be changed, but

the contents up to the point of the allocation size change remain the same.

Dynamic Memory Debugging

The Sun™ WorkShop package of tools is useful in ﬁnding and eliminating errors in

dynamic memory use. The Run Time Checking (RTC) facility of the Sun WorkShop

uses the functions that are described in this section to ﬁnd errors in dynamic memory

use.

RTC does not require the program be compiled using -g in order to ﬁnd all errors.

However, symbolic (-g) information is sometimes needed to guarantee the correctness

of certain errors, particularly errors that are read from uninitialized memory. For this

reason, certain errors are suppressed if no symbolic information is available. These

errors are rui for a.out and rui + aib + air for shared libraries. This behavior

can be changed by using suppress and unsuppress.

18 Programming Interfaces Guide • December 2003

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