|C H A P T E R 12|
Libraries provide a way to share code among several applications and a way to reduce the complexity of very large applications. The C++ compiler gives you access to a variety of libraries. This chapter explains how to use these libraries.
The Solaris operating system comes with several libraries installed in /usr/lib. Most of these libraries have a C interface. Of these, the libc and libm, libraries are linked by the CC driver by default. The library libthread is linked if you use the -mt option. To link any other system library, use the appropriate -l option at link time. For example, to link the libdemangle library, pass -ldemangle on the CC command line at link time:
The C++ compiler has its own runtime support libraries. All C++ applications are linked to these libraries by the CC driver. The C++ compiler also comes with several other useful libraries, as explained in the following section.
Several libraries are shipped with the C++ compiler. Some of these libraries are available only in compatibility mode (-compat=4), some are available only in the standard mode (-compat=5), and some are available in both modes. The libgc and libdemangle libraries have a C interface and can be linked to an application in either mode.
The following table lists the libraries that are shipped with the C++ compiler and the modes in which they are available.
Note - Do not redefine or modify any of the configuration macros for STLport, Rogue Wave or Sun Microsystems C++ libraries. The libraries are configured and built in a way that works with the C++ compiler. libCstd and Tool.h++ are configured to inter-operate so modifying the configuration macros results in programs that will not compile, will not link, or do not run properly.
A brief description of each of these libraries follows.
libCstd: This is the C++ standard library. In particular, it includes iostreams. If you have existing sources that use the classic iostreams and you want to make use of the standard iostreams, you have to modify your sources to conform to the new interface. See the C++ Standard Library Reference online manual for details. You can access this manual by pointing your web browser to:
If your compiler software is not installed in the /opt directory, ask your system administrator for the equivalent path on your system.
You can access this documentation by pointing your web browser to:
If your compiler software is not installed in the /opt directory, ask your system administrator for the equivalent path on your system.
Additional information can be found in the gcFixPrematureFrees(3) and gcInitialize(3) man pages.
The man pages associated with the libraries described in this section are located in:
To access these man pages, ensure that your MANPATH includes /opt/SUNWspro/man (or the equivalent path on your system for the compiler software). For instructions on setting your MANPATH, see Section , Accessing the Man Pages in "Before You Begin" at the front of this book.
To access man pages for the C++ libraries, type:
To access man pages for version 4.2 of the C++ libraries, type:
You can also access the man pages by pointing your browser to:
Some of the C++ libraries are linked by default by the CC driver, while others need to be linked explicitly. In the standard mode, the following libraries are linked by default by the CC driver:
-lCstd -lCrun -lm -lc
In compatibility mode (-compat), the following libraries are linked by default:
-lC -lm -lc
See Section A.2.48, -library=l[,l...] for more information.
The CC driver provides several options to help you use libraries.
A library that is specified using both -library and -staticlib options will be linked statically. Some examples:
By default, CC links various sets of system libraries depending on the command line options. If you specify -xnolib (or -nolib), CC links only those libraries that are specified explicitly with the -l option on the command line. (When -xnolib or -nolib is used, the -library option is ignored, if present.)
The -R option allows you to build dynamic library search paths into the executable file. At execution time, the runtime linker searches these paths for the shared libraries needed by the application. The CC driver passes -R/opt/SUNWspro/lib to ld by default (if the compiler is installed in the standard location). You can use -norunpath to disable building the default path for shared libraries into the executable.
Generally, two steps are involved in using a class library:
1. Include the appropriate header in your source code.
2. Link your program with the object library.
The C++ compiler provides two implementations of iostreams:
If you have existing C++ sources, your code might look like the following example, which uses classic iostreams.
The following command compiles in compatibility mode and links prog1.cc into an executable program called prog1. The classic iostream library is part of libC, which is linked by default in compatibility mode.
The next example uses standard iostreams.
The following command compiles and links prog2.cc into an executable program called prog2. The program is compiled in standard mode and libCstd, which includes the standard iostream library, is linked by default.
For more information about libCstd, see Chapter 13. For more information about libiostream, see Chapter 14.
For a full discussion of compilation modes, see the C++ Migration Guide.
The standard library provides a templatized complex library that is similar to the complex library provided with the C++ 4.2 compiler. If you compile in standard mode, you must use <complex> instead of <complex.h>. You cannot use <complex> in compatibility mode.
In compatibility mode, you must explicitly ask for the complex library when linking. In standard mode, the complex library is included in libCstd, and is linked by default.
There is no complex.h header for standard mode. In C++ 4.2, "complex" is the name of a class, but in standard C++, "complex" is the name of a template. It is not possible to provide typedefs that allow old code to work unchanged. Therefore, code written for 4.2 that uses complex numbers will need some straightforward editing to work with the standard library. For example, the following code was written for 4.2 and will compile in compatibility mode.
The following example compiles and links ex1.cc in compatibility mode, and then executes the program.
Here is ex1.cc rewritten as ex2.cc to compile in standard mode:
The following example compiles and links the rewritten ex2.cc in standard mode, and then executes the program.
For more information about using the complex arithmetic library, see Chapter 15.
The following table shows the compiler options for linking the C++ libraries. See Section A.2.48, -library=l[,l...] for more information.
The CC driver links in shared versions of several libraries by default, including libc and libm, by passing a -llib option for each of the default libraries to the linker. (See Section 12.2.3, Default C++ Libraries for the list of default libraries for compatibility mode and standard mode.)
If you want any of these default libraries to be linked statically, you can use the -library option along with the -staticlib option to link a C++ library statically. This alternative is much easier than the one described earlier. For example:
In this example, the -library option is not explicitly included in the command. In this case the -library option is not necessary because the default setting for -library is Cstd,Crun in standard mode (the default mode).
Alternately, you can use the -xnolib compiler option. With the -xnolib option, the driver does not pass any -l options to ld; you must pass these options yourself. The following example shows how you would link statically with libCrun, and dynamically with libm, and libc in the Solaris 8, or Solaris 9 operating systems:
The order of the -l options is important. The -lCstd, -lCrun, and -lm options appear before -lc.
Some CC options link to other libraries. These library links are also suppressed by -xnolib. For example, using the -mt option causes the CC driver to pass -lthread to ld. However, if you use both -mt and -xnolib, the CC driver does not pass -lthread to ld. See Section A.2.142, -xnolib for more information. See Linker and Libraries Guide for more information about ld.
The following shared libraries are included with the C++ compiler:
The occurrence of each shared object linked with the program is recorded in the resulting executable (a.out file); this information is used by ld.so to perform dynamic link editing at runtime. Because the work of incorporating the library code into an address space is deferred, the runtime behavior of the program using a shared library is sensitive to an environment change--that is, moving a library from one directory to another. For example, if your program is linked with libcomplex.so.5 in /opt/SUNWspro/lib, and the libcomplex.so.5 library is later moved into /opt2/SUNWspro/lib, the following message is displayed when you run the binary code:
You can still run the old binary code without recompiling it by setting the environment variable LD_LIBRARY_PATH to the new library directory.
In a C shell:
In a Bourne shell:
The LD_LIBRARY_PATH has a list of directories, usually separated by colons. When you run a C++ program, the dynamic loader searches the directories in LD_LIBRARY_PATH before it searches the default directories.
Use the ldd command as shown in the following example to see which libraries are linked dynamically in your executable:
This step should rarely be necessary, because the shared libraries are seldom moved.
See Linker and Libraries Guide for more information on using shared libraries.
Replacing the standard library that is distributed with the compiler is risky, and good results are not guaranteed. The basic operation is to disable the standard headers and library supplied with the compiler, and to specify the directories where the new header files and library are found, as well as the name of the library itself.
The compiler supports the STLport implementation of the standard library. See Section 13.3, STLport for more information.
You can replace most of the standard library and its associated headers. The replaced library is libCstd, and the associated headers are listed in the following table:
The replaceable part of the library consists of what is loosely known as "STL", plus the string classes, the iostream classes, and their helper classes. Because these classes and headers are interdependent, replacing just a portion of them is unlikely to work. You should replace all of the headers and all of libCstd if you replace any part.
The standard headers <exception>, <new>, and <typeinfo> are tied tightly to the compiler itself and to libCrun, and cannot reliably be replaced. The library libCrun contains many "helper" functions that the compiler depends on, and cannot be replaced.
The 17 standard headers inherited from C (<stdlib.h>, <stdio.h>, <string.h>, and so forth) are tied tightly to the Solaris operating system and the basic Solaris runtime library libc, and cannot reliably be replaced. The C++ versions of those headers (<cstdlib>, <cstdio>, <cstring>, and so forth) are tied tightly to the basic C versions and cannot reliably be replaced.
To install the replacement library, you must first decide on the locations for the replacement headers and on the replacement for libCstd. For purposes of discussion, assume the headers are placed in /opt/mycstd/include and the library is placed in /opt/mycstd/lib. Assume the library is called libmyCstd.a. (It is often convenient if the library name starts with "lib".)
On each compilation, use the -I option to point to the location where the headers are installed. In addition, use the -library=no%Cstd option to prevent finding the compiler's own versions of the libCstd headers. For example:
During compiling, the -library=no%Cstd option prevents searching the directory where the compiler's own version of these headers is located.
On each program or library link, use the -library=no%Cstd option to prevent finding the compiler's own libCstd, the -L option to point to the directory where the replacement library is, and the -l option to specify the replacement library. Example:
Alternatively, you can use the full path name of the library directly, and omit using the -L and -l options. For example:
During linking, the -library=no%Cstd option prevents linking the compiler's own version of libCstd.
C has 17 standard headers (<stdio.h>, <string.h>, <stdlib.h>, and others). These headers are delivered as part of the Solaris operating system, in the directory /usr/include. C++ has those same headers, with the added requirement that the various declared names appear in both the global namespace and in namespace std. On versions of the Solaris operating system prior to version 8, the C++ compiler supplies its own versions of these headers instead of replacing those in the /usr/include directory.
C++ also has a second version of each of the C standard headers (<cstdio>, <cstring>, and <cstdlib>, and others) with the various declared names appearing only in namespace std. Finally, C++ adds 32 of its own standard headers (<string>, <utility>, <iostream>, and others).
The obvious implementation of the standard headers would use the name found in C++ source code as the name of a text file to be included. For example, the standard headers <string> (or <string.h>) would refer to a file named string (or string.h) in some directory. That obvious implementation has the following drawbacks:
To solve these problems, the compiler include directory contains a file with the same name as the header, along with a symbolic link to it that has the unique suffix .SUNWCCh (SUNW is the prefix for all compiler-related packages, CC is the C++ compiler, and h is the usual suffix for header files). When you specify <string>, the compiler rewrites it to <string.SUNWCCh> and searches for that name. The suffixed name will be found only in the compiler's own include directory. If the file so found is a symbolic link (which it normally is), the compiler dereferences the link exactly once and uses the result (string in this case) as the file name for error messages and debugger references. The compiler uses the suffixed name when emitting file dependency information.
The name rewriting occurs only for the two forms of the 17 standard C headers and the 32 standard C++ headers, only when they appear in angle brackets and without any path specified. If you use quotes instead of angle brackets, specify any path components, or specify some other header, no rewriting occurs.
The following table illustrates common situations.
If the compiler does not find header.SUNWCCh, the compiler restarts the search looking for the name as provided in the #include directive. For example, given the directive #include <string>, the compiler attempts to find a file named string.SUNWCCh. If that search fails, the compiler looks for a file named string.
Because of the search algorithm described in Section 12.7.5, Standard Header Implementation, you do not need to supply SUNWCCh versions of the replacement headers described in Section 12.7.3, Installing the Replacement Library. But you might run into some of the described problems. If so, the recommended solution is to add symbolic links having the suffix .SUNWCCh for each of the unsuffixed headers. That is, for file utility, you would run the command
When the compiler looks first for utility.SUNWCCh, it will find it, and not be confused by any other file or directory called utility.
Replacing the standard C headers is not supported. If you nevertheless wish to provide your own versions of standard headers, the recommended procedure is as follows:
For example, suppose you have replacements for <stdio.h> and <cstdio>. Put the files stdio.h and cstdio in directory /myproject/myhdr. In that directory, run these commands:
Use the option -I/myproject/mydir on every compilation.