2004-07-17 10:04:49 +00:00
|
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
|
|
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
|
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<title>System Library</title>
|
|
|
|
|
<link rel="stylesheet" href="llvm.css" type="text/css">
|
|
|
|
|
</head>
|
|
|
|
|
<body>
|
|
|
|
|
|
2004-07-21 18:02:43 +00:00
|
|
|
<div class="doc_title">System Library</div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<ul>
|
|
|
|
|
<li><a href="#abstract">Abstract</a></li>
|
2005-01-05 18:17:10 +00:00
|
|
|
<li><a href="#requirements">Keeping LLVM Portable</a>
|
2004-07-17 10:04:49 +00:00
|
|
|
<ol>
|
2005-01-05 18:17:10 +00:00
|
|
|
<li><a href="#headers">Don't Include System Headers</a></li>
|
|
|
|
|
<li><a href="#expose">Don't Expose System Headers</a></li>
|
2004-08-27 02:08:04 +00:00
|
|
|
<li><a href="#c_headers">Allow Standard C Header Files</a></li>
|
|
|
|
|
<li><a href="#cpp_headers">Allow Standard C++ Header Files</a></li>
|
2005-01-05 18:17:10 +00:00
|
|
|
<li><a href="#highlev">High-Level Interface</a></li>
|
2004-07-17 10:04:49 +00:00
|
|
|
<li><a href="#nofunc">No Exposed Functions</a></li>
|
|
|
|
|
<li><a href="#nodata">No Exposed Data</a></li>
|
2004-11-21 14:58:12 +00:00
|
|
|
<li><a href="#nodupl">No Duplicate Implementations</a></li>
|
2004-08-27 02:08:04 +00:00
|
|
|
<li><a href="#nounused">No Unused Functionality</a></li>
|
2004-07-17 10:04:49 +00:00
|
|
|
<li><a href="#virtuals">No Virtual Methods</a></li>
|
2005-01-05 18:17:10 +00:00
|
|
|
<li><a href="#softerrors">Minimize Soft Errors</a></li>
|
|
|
|
|
<li><a href="#throw">Throw Only std::string</a></li>
|
|
|
|
|
<li><a href="#throw_spec">No throw() Specifications</a></li>
|
|
|
|
|
<li><a href="#organization">Code Organization</a></li>
|
|
|
|
|
<li><a href="#semantics">Consistent Semantics</a></li>
|
2004-07-17 10:04:49 +00:00
|
|
|
<li><a href="#bug">Tracking Bugzilla Bug: 351</a></li>
|
|
|
|
|
</ol></li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<div class="doc_author">
|
2007-03-30 12:22:09 +00:00
|
|
|
<p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
|
<div class="doc_section"><a name="abstract">Abstract</a></div>
|
|
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>This document provides some details on LLVM's System Library, located in
|
|
|
|
|
the source at <tt>lib/System</tt> and <tt>include/llvm/System</tt>. The
|
|
|
|
|
library's purpose is to shield LLVM from the differences between operating
|
|
|
|
|
systems for the few services LLVM needs from the operating system. Much of
|
|
|
|
|
LLVM is written using portability features of standard C++. However, in a few
|
|
|
|
|
areas, system dependent facilities are needed and the System Library is the
|
|
|
|
|
wrapper around those system calls.</p>
|
|
|
|
|
<p>By centralizing LLVM's use of operating system interfaces, we make it
|
|
|
|
|
possible for the LLVM tool chain and runtime libraries to be more easily
|
|
|
|
|
ported to new platforms since (theoretically) only <tt>lib/System</tt> needs
|
|
|
|
|
to be ported. This library also unclutters the rest of LLVM from #ifdef use
|
|
|
|
|
and special cases for specific operating systems. Such uses are replaced
|
|
|
|
|
with simple calls to the interfaces provided in <tt>include/llvm/System</tt>.
|
|
|
|
|
</p>
|
|
|
|
|
<p>Note that the System Library is not intended to be a complete operating
|
|
|
|
|
system wrapper (such as the Adaptive Communications Environment (ACE) or
|
|
|
|
|
Apache Portable Runtime (APR)), but only provides the functionality necessary
|
|
|
|
|
to support LLVM.
|
2004-08-27 02:08:04 +00:00
|
|
|
<p>The System Library was written by Reid Spencer who formulated the
|
2005-01-05 18:17:10 +00:00
|
|
|
design based on similar work originating from the eXtensible Programming
|
|
|
|
|
System (XPS). Several people helped with the effort; especially,
|
|
|
|
|
Jeff Cohen and Henrik Bach on the Win32 port.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
|
<div class="doc_section">
|
2005-01-05 18:17:10 +00:00
|
|
|
<a name="requirements">Keeping LLVM Portable</a>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>In order to keep LLVM portable, LLVM developers should adhere to a set of
|
|
|
|
|
portability rules associated with the System Library. Adherence to these rules
|
|
|
|
|
should help the System Library achieve its goal of shielding LLVM from the
|
|
|
|
|
variations in operating system interfaces and doing so efficiently. The
|
|
|
|
|
following sections define the rules needed to fulfill this objective.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="headers">Don't Inlcude System Headers</a>
|
|
|
|
|
</div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>Except in <tt>lib/System</tt>, no LLVM source code should directly
|
|
|
|
|
<tt>#include</tt> a system header. Care has been taken to remove all such
|
|
|
|
|
<tt>#includes</tt> from LLVM while <tt>lib/System</tt> was being
|
|
|
|
|
developed. Specifically this means that header files like "unistd.h",
|
|
|
|
|
"windows.h", "stdio.h", and "string.h" are forbidden to be included by LLVM
|
|
|
|
|
source code outside the implementation of <tt>lib/System</tt>.</p>
|
|
|
|
|
<p>To obtain system-dependent functionality, existing interfaces to the system
|
|
|
|
|
found in <tt>include/llvm/System</tt> should be used. If an appropriate
|
|
|
|
|
interface is not available, it should be added to <tt>include/llvm/System</tt>
|
|
|
|
|
and implemented in <tt>lib/System</tt> for all supported platforms.</p>
|
2004-08-27 02:08:04 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="expose">Don't Expose System Headers</a>
|
|
|
|
|
</div>
|
2005-01-05 18:21:39 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>The System Library must shield LLVM from <em>all</em> system headers. To
|
|
|
|
|
obtain system level functionality, LLVM source must
|
|
|
|
|
<tt>#include "llvm/System/Thing.h"</tt> and nothing else. This means that
|
|
|
|
|
<tt>Thing.h</tt> cannot expose any system header files. This protects LLVM
|
|
|
|
|
from accidentally using system specific functionality and only allows it
|
|
|
|
|
via the <tt>lib/System</tt> interface.</p>
|
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:21:39 +00:00
|
|
|
<div class="doc_subsection"><a name="c_headers">Use Standard C Headers</a></div>
|
2004-08-27 02:08:04 +00:00
|
|
|
<div class="doc_text">
|
|
|
|
|
<p>The <em>standard</em> C headers (the ones beginning with "c") are allowed
|
2005-01-05 18:17:10 +00:00
|
|
|
to be exposed through the <tt>lib/System</tt> interface. These headers and
|
|
|
|
|
the things they declare are considered to be platform agnostic. LLVM source
|
|
|
|
|
files may include them directly or obtain their inclusion through
|
|
|
|
|
<tt>lib/System</tt> interfaces.</p>
|
2004-08-27 02:08:04 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="cpp_headers">Use Standard C++ Headers</a>
|
2004-08-27 02:08:04 +00:00
|
|
|
</div>
|
|
|
|
|
<div class="doc_text">
|
|
|
|
|
<p>The <em>standard</em> C++ headers from the standard C++ library and
|
2005-01-05 18:17:10 +00:00
|
|
|
standard template library may be exposed through the <tt>lib/System</tt>
|
2004-08-27 02:08:04 +00:00
|
|
|
interface. These headers and the things they declare are considered to be
|
|
|
|
|
platform agnostic. LLVM source files may include them or obtain their
|
|
|
|
|
inclusion through lib/System interfaces.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="highlev">High Level Interface</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>The entry points specified in the interface of lib/System must be aimed at
|
|
|
|
|
completing some reasonably high level task needed by LLVM. We do not want to
|
|
|
|
|
simply wrap each operating system call. It would be preferable to wrap several
|
|
|
|
|
operating system calls that are always used in conjunction with one another by
|
|
|
|
|
LLVM.</p>
|
|
|
|
|
<p>For example, consider what is needed to execute a program, wait for it to
|
|
|
|
|
complete, and return its result code. On Unix, this involves the following
|
|
|
|
|
operating system calls: <tt>getenv, fork, execve,</tt> and <tt>wait</tt>. The
|
|
|
|
|
correct thing for lib/System to provide is a function, say
|
|
|
|
|
<tt>ExecuteProgramAndWait</tt>, that implements the functionality completely.
|
|
|
|
|
what we don't want is wrappers for the operating system calls involved.</p>
|
|
|
|
|
<p>There must <em>not</em> be a one-to-one relationship between operating
|
|
|
|
|
system calls and the System library's interface. Any such interface function
|
|
|
|
|
will be suspicious.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="nounused">No Unused Functionality</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>There must be no functionality specified in the interface of lib/System
|
|
|
|
|
that isn't actually used by LLVM. We're not writing a general purpose
|
|
|
|
|
operating system wrapper here, just enough to satisfy LLVM's needs. And, LLVM
|
|
|
|
|
doesn't need much. This design goal aims to keep the lib/System interface
|
|
|
|
|
small and understandable which should foster its actual use and adoption.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2004-08-27 02:08:04 +00:00
|
|
|
<div class="doc_subsection"><a name="nodupl">No Duplicate Implementations</a>
|
|
|
|
|
</div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2004-08-27 02:08:04 +00:00
|
|
|
<p>The implementation of a function for a given platform must be written
|
|
|
|
|
exactly once. This implies that it must be possible to apply a function's
|
|
|
|
|
implementation to multiple operating systems if those operating systems can
|
2005-01-05 18:17:10 +00:00
|
|
|
share the same implementation. This rule applies to the set of operating
|
|
|
|
|
systems supported for a given class of operating system (e.g. Unix, Win32).
|
|
|
|
|
</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
2005-01-05 18:17:10 +00:00
|
|
|
<!-- ======================================================================= -->
|
|
|
|
|
<div class="doc_subsection"><a name="virtuals">No Virtual Methods</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>The System Library interfaces can be called quite frequently by LLVM. In
|
|
|
|
|
order to make those calls as efficient as possible, we discourage the use of
|
|
|
|
|
virtual methods. There is no need to use inheritance for implementation
|
|
|
|
|
differences, it just adds complexity. The <tt>#include</tt> mechanism works
|
|
|
|
|
just fine.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
2004-08-27 02:08:04 +00:00
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="nofunc">No Exposed Functions</a></div>
|
2004-08-27 02:08:04 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>Any functions defined by system libraries (i.e. not defined by lib/System)
|
|
|
|
|
must not be exposed through the lib/System interface, even if the header file
|
|
|
|
|
for that function is not exposed. This prevents inadvertent use of system
|
|
|
|
|
specific functionality.</p>
|
|
|
|
|
<p>For example, the <tt>stat</tt> system call is notorious for having
|
|
|
|
|
variations in the data it provides. <tt>lib/System</tt> must not declare
|
|
|
|
|
<tt>stat</tt> nor allow it to be declared. Instead it should provide its own
|
|
|
|
|
interface to discovering information about files and directories. Those
|
|
|
|
|
interfaces may be implemented in terms of <tt>stat</tt> but that is strictly
|
|
|
|
|
an implementation detail. The interface provided by the System Library must
|
|
|
|
|
be implemented on all platforms (even those without <tt>stat</tt>).</p>
|
2004-08-27 02:08:04 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="nodata">No Exposed Data</a></div>
|
2004-08-27 02:08:04 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>Any data defined by system libraries (i.e. not defined by lib/System) must
|
|
|
|
|
not be exposed through the lib/System interface, even if the header file for
|
|
|
|
|
that function is not exposed. As with functions, this prevents inadvertent use
|
|
|
|
|
of data that might not exist on all platforms.</p>
|
2004-08-27 02:08:04 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="softerrors">Minimize Soft Errors</a></div>
|
2004-08-27 02:08:04 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>Operating system interfaces will generally provide error results for every
|
2004-08-27 02:08:04 +00:00
|
|
|
little thing that could go wrong. In almost all cases, you can divide these
|
|
|
|
|
error results into two groups: normal/good/soft and abnormal/bad/hard. That
|
|
|
|
|
is, some of the errors are simply information like "file not found",
|
|
|
|
|
"insufficient privileges", etc. while other errors are much harder like
|
2005-01-05 18:17:10 +00:00
|
|
|
"out of space", "bad disk sector", or "system call interrupted". We'll call
|
|
|
|
|
the first group "<i>soft</i>" errors and the second group "<i>hard</i>"
|
|
|
|
|
errors.<p>
|
2004-08-27 02:08:04 +00:00
|
|
|
<p>lib/System must always attempt to minimize soft errors and always just
|
|
|
|
|
throw a std::string on hard errors. This is a design requirement because the
|
|
|
|
|
minimization of soft errors can affect the granularity and the nature of the
|
|
|
|
|
interface. In general, if you find that you're wanting to throw soft errors,
|
|
|
|
|
you must review the granularity of the interface because it is likely you're
|
|
|
|
|
trying to implement something that is too low level. The rule of thumb is to
|
2005-01-05 18:17:10 +00:00
|
|
|
provide interface functions that <em>can't</em> fail, except when faced with
|
|
|
|
|
hard errors.</p>
|
2004-08-27 02:08:04 +00:00
|
|
|
<p>For a trivial example, suppose we wanted to add an "OpenFileForWriting"
|
|
|
|
|
function. For many operating systems, if the file doesn't exist, attempting
|
|
|
|
|
to open the file will produce an error. However, lib/System should not
|
|
|
|
|
simply throw that error if it occurs because its a soft error. The problem
|
|
|
|
|
is that the interface function, OpenFileForWriting is too low level. It should
|
|
|
|
|
be OpenOrCreateFileForWriting. In the case of the soft "doesn't exist" error,
|
|
|
|
|
this function would just create it and then open it for writing.</p>
|
|
|
|
|
<p>This design principle needs to be maintained in lib/System because it
|
|
|
|
|
avoids the propagation of soft error handling throughout the rest of LLVM.
|
|
|
|
|
Hard errors will generally just cause a termination for an LLVM tool so don't
|
|
|
|
|
be bashful about throwing them.</p>
|
|
|
|
|
<p>Rules of thumb:</p>
|
|
|
|
|
<ol>
|
|
|
|
|
<li>Don't throw soft errors, only hard errors.</li>
|
|
|
|
|
<li>If you're tempted to throw a soft error, re-think the interface.</li>
|
|
|
|
|
<li>Handle internally the most common normal/good/soft error conditions
|
|
|
|
|
so the rest of LLVM doesn't have to.</li>
|
|
|
|
|
</ol>
|
|
|
|
|
</div>
|
|
|
|
|
|
2004-07-17 10:04:49 +00:00
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="throw">Throw Only std::string</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>If an error occurs that lib/System cannot handle, the only action taken by
|
|
|
|
|
lib/System is to throw an instance of std:string. The contents of the string
|
|
|
|
|
must explain both what happened and the context in which it happened. The
|
|
|
|
|
format of the string should be a (possibly empty) list of contexts each
|
|
|
|
|
terminated with a : and a space, followed by the error message, optionally
|
|
|
|
|
followed by a reason, and optionally followed by a suggestion.</p>
|
|
|
|
|
<p>For example, failure to open a file named "foo" could result in a message
|
|
|
|
|
like:</p>
|
|
|
|
|
<ul><li>foo: Unable to open file because it doesn't exist."</li></ul>
|
|
|
|
|
<p>The "foo:" part is the context. The "Unable to open file" part is the error
|
|
|
|
|
message. The "because it doesn't exist." part is the reason. This message has
|
|
|
|
|
no suggestion. Where possible, the implementation of lib/System should use
|
|
|
|
|
operating system specific facilities for converting the error code returned by
|
|
|
|
|
a system call into an error message. This will help to make the error message
|
|
|
|
|
more familiar to users of that type of operating system.</p>
|
|
|
|
|
<p>Note that this requirement precludes the throwing of any other exceptions.
|
|
|
|
|
For example, various C++ standard library functions can cause exceptions to be
|
|
|
|
|
thrown (e.g. out of memory situation). In all cases, if there is a possibility
|
|
|
|
|
that non-string exceptions could be thrown, the lib/System library must ensure
|
|
|
|
|
that the exceptions are translated to std::string form.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="throw_spec">No throw Specifications</a>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>None of the lib/System interface functions may be declared with C++
|
|
|
|
|
<tt>throw()</tt> specifications on them. This requirement makes sure that the
|
|
|
|
|
compiler does not insert additional exception handling code into the interface
|
|
|
|
|
functions. This is a performance consideration: lib/System functions are at
|
|
|
|
|
the bottom of many call chains and as such can be frequently called. We
|
|
|
|
|
need them to be as efficient as possible.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="organization">Code Organization</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>Implementations of the System Library interface are separated by their
|
|
|
|
|
general class of operating system. Currently only Unix and Win32 classes are
|
|
|
|
|
defined but more could be added for other operating system classifications.
|
|
|
|
|
To distinguish which implementation to compile, the code in lib/System uses
|
|
|
|
|
the LLVM_ON_UNIX and LLVM_ON_WIN32 #defines provided via configure through the
|
|
|
|
|
llvm/Config/config.h file. Each source file in lib/System, after implementing
|
|
|
|
|
the generic (operating system independent) functionality needs to include the
|
|
|
|
|
correct implementation using a set of <tt>#if defined(LLVM_ON_XYZ)</tt>
|
|
|
|
|
directives. For example, if we had lib/System/File.cpp, we'd expect to see in
|
|
|
|
|
that file:</p>
|
|
|
|
|
<pre><tt>
|
|
|
|
|
#if defined(LLVM_ON_UNIX)
|
|
|
|
|
#include "Unix/File.cpp"
|
|
|
|
|
#endif
|
|
|
|
|
#if defined(LLVM_ON_WIN32)
|
|
|
|
|
#include "Win32/File.cpp"
|
|
|
|
|
#endif
|
|
|
|
|
</tt></pre>
|
|
|
|
|
<p>The implementation in lib/System/Unix/File.cpp should handle all Unix
|
|
|
|
|
variants. The implementation in lib/System/Win32/File.cpp should handle all
|
|
|
|
|
Win32 variants. What this does is quickly differentiate the basic class of
|
|
|
|
|
operating system that will provide the implementation. The specific details
|
|
|
|
|
for a given platform must still be determined through the use of
|
|
|
|
|
<tt>#ifdef</tt>.</p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2005-01-05 18:17:10 +00:00
|
|
|
<div class="doc_subsection"><a name="semantics">Consistent Semantics</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2005-01-05 18:17:10 +00:00
|
|
|
<p>The implementation of a lib/System interface can vary drastically between
|
|
|
|
|
platforms. That's okay as long as the end result of the interface function
|
|
|
|
|
is the same. For example, a function to create a directory is pretty straight
|
|
|
|
|
forward on all operating system. System V IPC on the other hand isn't even
|
|
|
|
|
supported on all platforms. Instead of "supporting" System V IPC, lib/System
|
|
|
|
|
should provide an interface to the basic concept of inter-process
|
|
|
|
|
communications. The implementations might use System V IPC if that was
|
|
|
|
|
available or named pipes, or whatever gets the job done effectively for a
|
|
|
|
|
given operating system. In all cases, the interface and the implementation
|
|
|
|
|
must be semantically consistent. </p>
|
2004-07-17 10:04:49 +00:00
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
2004-07-17 18:50:19 +00:00
|
|
|
<div class="doc_subsection"><a name="bug">Bug 351</a></div>
|
2004-07-17 10:04:49 +00:00
|
|
|
<div class="doc_text">
|
2006-03-14 05:39:39 +00:00
|
|
|
<p>See <a href="http://llvm.org/PR351">bug 351</a>
|
2004-07-17 10:04:49 +00:00
|
|
|
for further details on the progress of this work</p>
|
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
|
|
|
|
|
|
<hr>
|
|
|
|
|
<address>
|
|
|
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
2008-12-11 17:34:48 +00:00
|
|
|
src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
|
2004-07-17 10:04:49 +00:00
|
|
|
<a href="http://validator.w3.org/check/referer"><img
|
2008-12-11 17:34:48 +00:00
|
|
|
src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
|
2004-07-17 10:04:49 +00:00
|
|
|
|
|
|
|
|
<a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
|
2006-03-14 05:39:39 +00:00
|
|
|
<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
|
2004-07-17 10:04:49 +00:00
|
|
|
Last modified: $Date$
|
|
|
|
|
</address>
|
|
|
|
|
</body>
|
|
|
|
|
</html>
|
