📄 vms-misc.html
字号:
<html lang="en">
<head>
<title>Using the GNU Compiler Collection (GCC)</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
<meta name="generator" content="makeinfo 4.3">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home">
<!--
Copyright © 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
<p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding
Free Software", the Front-Cover texts being (a) (see below), and with
the Back-Cover Texts being (b) (see below). A copy of the license is
included in the section entitled "GNU Free Documentation License".
<p>(a) The FSF's Front-Cover Text is:
<p>A GNU Manual
<p>(b) The FSF's Back-Cover Text is:
<p>You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.-->
</head>
<body>
<div class="node">
<p>
Node:<a name="VMS%20Misc">VMS Misc</a>,
Previous:<a rel="previous" accesskey="p" href="Global-Declarations.html#Global%20Declarations">Global Declarations</a>,
Up:<a rel="up" accesskey="u" href="VMS.html#VMS">VMS</a>
<hr><br>
</div>
<h3 class="section">Other VMS Issues</h3>
<p>GCC automatically arranges for <code>main</code> to return 1 by default if
you fail to specify an explicit return value. This will be interpreted
by VMS as a status code indicating a normal successful completion.
Version 1 of GCC did not provide this default.
<p>GCC on VMS works only with the GNU assembler, GAS. You need version
1.37 or later of GAS in order to produce value debugging information for
the VMS debugger. Use the ordinary VMS linker with the object files
produced by GAS.
<p>Under previous versions of GCC, the generated code would occasionally
give strange results when linked to the sharable <code>VAXCRTL</code> library.
Now this should work.
<p>A caveat for use of <code>const</code> global variables: the <code>const</code>
modifier must be specified in every external declaration of the variable
in all of the source files that use that variable. Otherwise the linker
will issue warnings about conflicting attributes for the variable. Your
program will still work despite the warnings, but the variable will be
placed in writable storage.
<p>Although the VMS linker does distinguish between upper and lower case
letters in global symbols, most VMS compilers convert all such symbols
into upper case and most run-time library routines also have upper case
names. To be able to reliably call such routines, GCC (by means of
the assembler GAS) converts global symbols into upper case like other
VMS compilers. However, since the usual practice in C is to distinguish
case, GCC (via GAS) tries to preserve usual C behavior by augmenting
each name that is not all lower case. This means truncating the name
to at most 23 characters and then adding more characters at the end
which encode the case pattern of those 23. Names which contain at
least one dollar sign are an exception; they are converted directly into
upper case without augmentation.
<p>Name augmentation yields bad results for programs that use precompiled
libraries (such as Xlib) which were generated by another compiler. You
can use the compiler option <code>/NOCASE_HACK</code> to inhibit augmentation;
it makes external C functions and variables case-independent as is usual
on VMS. Alternatively, you could write all references to the functions
and variables in such libraries using lower case; this will work on VMS,
but is not portable to other systems. The compiler option <code>/NAMES</code>
also provides control over global name handling.
<p>Function and variable names are handled somewhat differently with G++.
The GNU C++ compiler performs <dfn>name mangling</dfn> on function
names, which means that it adds information to the function name to
describe the data types of the arguments that the function takes. One
result of this is that the name of a function can become very long.
Since the VMS linker only recognizes the first 31 characters in a name,
special action is taken to ensure that each function and variable has a
unique name that can be represented in 31 characters.
<p>If the name (plus a name augmentation, if required) is less than 32
characters in length, then no special action is performed. If the name
is longer than 31 characters, the assembler (GAS) will generate a
hash string based upon the function name, truncate the function name to
23 characters, and append the hash string to the truncated name. If the
<code>/VERBOSE</code> compiler option is used, the assembler will print both
the full and truncated names of each symbol that is truncated.
<p>The <code>/NOCASE_HACK</code> compiler option should not be used when you are
compiling programs that use libg++. libg++ has several instances of
objects (i.e. <code>Filebuf</code> and <code>filebuf</code>) which become
indistinguishable in a case-insensitive environment. This leads to
cases where you need to inhibit augmentation selectively (if you were
using libg++ and Xlib in the same program, for example). There is no
special feature for doing this, but you can get the result by defining a
macro for each mixed case symbol for which you wish to inhibit
augmentation. The macro should expand into the lower case equivalent of
itself. For example:
<pre class="example"> #define StuDlyCapS studlycaps
</pre>
<p>These macro definitions can be placed in a header file to minimize the
number of changes to your source code.
</body></html>
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -