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Solaris 64-bit Developer's Guide |
3. Comparing 32-bit Interfaces and 64-bit Interfaces
5. The Development Environment
LD_LIBRARY_PATH Environment Variable
Packaging 32-bit and 64-bit Applications
Placement of Libraries and Programs
Application Naming Conventions
The build environment includes the system headers, compilation system, and libraries. These are explained in the sections that follow.
A single set of system headers supports both 32-bit and 64-bit compilation environments. You do not need to specify a different include path for the 64-bit compilation environment.
To better understand the changes made to the headers for support of the 64-bit environment, you should understand the various definitions in the header <sys/isa_defs.h>. This header contains a group of well known #defines and sets these for each instruction set architecture. Inclusion of <sys/types.h> automatically includes <sys/isa_defs.h>.
The symbols in the following table are defined by the compilation environment:
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Note - __i386 and __amd64 are mutually exclusive. The symbols __sparcv8 and __sparcv9 are mutually exclusive and are only relevant when the symbol __sparc is defined.
The following symbols are derived from some combination of the symbols above being defined:
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Note - The symbols _ILP32 and _LP64 are mutually exclusive.
If writing completely portable code is not possible, and specific 32-bit versus 64-bit code is required, make the code conditional using _ILP32 or _LP64. This makes the compilation environment machine independent and maximizes the portability of the application to all 64-bit platforms.
The Sun Studio C, C++, and Fortran compilation environments have been enhanced to support the creation of both 32-bit and 64-bit applications. The 10.0 release of the C compiler from Sun Studio provides 64–bit compilation support.
Native and cross-compilation modes are supported. The default compilation environment continues to produce 32-bit applications. While both modes are supported, they are still architecture-specific. It is not possible to create SPARC objects on x86 machines, nor x86 objects on SPARC machines with the Sun compilers. In the absence of a specification of the architecture or mode of compilation, the appropriate __sparcv8 or __i386 symbol is defined by default, and as part of this, _ILP32 is also defined. This maximizes interoperability with the existing applications and hardware base.
Starting with the Sun Studio 8 release, use the cc(1) -xarch=generic64 flag to enable the 64-bit compilation environment.
This generates LP64 code in ELF64 objects. ELF64 is a 64-bit object file format supporting 64-bit processors and architectures. This is in contrast to the ELF32 object files generated when compiling in the default 32-bit mode.
The -xarch=generic64 flag is used to generate 64-bit code on either 32-bit or 64-bit system. Using the 32-bit compiler you can build 64-bit objects on a 32-bit system; however, you cannot run the 64-bit objects on a 32–bit system. You need not specify the library path for the 64-bit libraries. If the -l or -L option is used to specify an additional library or library path and that path points only to 32-bit libraries, the linker detects this and fails with an error.
For a description of compiler options, see the Sun Studio 10: C User's Guide.
The Solaris operating environment provides shared libraries for both 32-bit and 64-bit compilation environments.
32-bit applications must link with 32-bit libraries, and 64-bit applications must link with 64-bit libraries. It is not possible to create or execute a 32-bit application using 64-bit libraries. The 32-bit libraries continue to be located in /usr/lib and /usr/ccs/lib. The 64-bit libraries are located in a subdirectory of the appropriate lib directory. Because the placement of the 32-bit libraries has not changed, 32-bit applications built on prior releases are binary compatible. Portable Makefiles should refer to any library directories using the 64 symbolic link.
In order to build 64-bit applications, you need 64-bit libraries. It is possible to do either native or cross-compilation, because the 64-bit libraries are available for both 32-bit and 64-bit environments. The compiler and other miscellaneous tools (for example; ld, ar, and as) are 32–bit programs capable of building 64-bit programs on 32-bit or 64-bit systems. Of course, a 64-bit program built on a system running the 32-bit operating system cannot execute in that 32-bit environment.
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