AIX Version 4.3 Differences Guide
AIX Version 4.3 Differences Guide
AIX Version 4.3 Differences Guide
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UNIX98 interface will add very little extra work. This does not mean that they<br />
have to change everything to UNIX98 conformance, just sbrk() in this case.<br />
The sbrk() function prototype in was changed to pass a long for all<br />
64-bit compilations; that is, if __64BIT__ is set. For 32-bit compilations, the sbrk()<br />
prototype will be conditionally compiled to generate the appropriate UNIX95 or<br />
UNIX98 prototype since the data-width between int and long does not change for<br />
32-bit. Code that wants to run 64-bit must either make sure it passes a long, or if<br />
it obeys UNIX98, it is required to include . The standards require<br />
header file inclusion. The prototype for sbrk(), which defines it as taking a long, is<br />
as follows:<br />
void *<br />
sbrk(intptr_t increment)<br />
intptr_t is a new type. Defined in , it maps to a long.<br />
3.3 Application Development<br />
Section 3.2, “64-Bit Core Design” on page 33, explained the design issues of <strong>AIX</strong><br />
<strong>4.3</strong> with respect to 64-bit application support. The changes in the core design of<br />
<strong>AIX</strong> have impacts on various components of the software development<br />
environment. This section describes what decisions have been made to provide a<br />
migration path from 32-bit to 64-bit applications. It shows the modifications that<br />
have been made to the most important tools in the software development area,<br />
such as the compiler, linker, and archiver.<br />
3.3.1 C Compiler<br />
This section discusses the implementation of 64-bit capabilities in the C for <strong>AIX</strong><br />
compiler. The C compiler provides supporting functions that can enable the<br />
usability of 64-bit C syntax and semantics.<br />
Each program compiled for execution on <strong>AIX</strong> is intended for execution in one<br />
particular target execution mode: 32-bit mode or 64-bit mode. The default<br />
compilation and assembly mode is 32-bit. This is the ILP32 model. The change<br />
from the default 32-bit to 64-bit mode is under user control. In the compiler, the<br />
option -q64 is used to change the compilation mode.<br />
The default execution mode is not directly controllable by the user processes but<br />
can be examined indirectly (for code dynamically targeted to multiple<br />
environments) through the pointer or long type size. The compiler provides<br />
porting assistance options wherever there are statements that can be<br />
ambiguously interpreted for the LP64 environment.<br />
When running 32-bit processes on 64-bit platforms, the execution is transparent<br />
and identical to executing on a 32-bit platform with no loss of performance. When<br />
trying to run 64-bit processes on 32-bit platforms, the execution will fail in an<br />
obvious manner.<br />
The 64-bit implementation in the C front end does not change the default<br />
behavior of the compiler. The compiler only changes the behavior of code when<br />
compiled in 64-bit mode. Code that was compiled in 32-bit mode that has no<br />
requirements for large address spaces (pointers) or large object sizes (arrays and<br />
dynamic heaps) will not need to be recompiled to work in 32-bit mode on a 64-bit<br />
56 <strong>AIX</strong> <strong>Version</strong> <strong>4.3</strong> <strong>Differences</strong> <strong>Guide</strong>
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