You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
234 lines
11 KiB
HTML
234 lines
11 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with the
|
||
|
|
Invariant Sections being "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".
|
||
|
|
|
||
|
|
(a) The FSF's Front-Cover Text is:
|
||
|
|
|
||
|
|
A GNU Manual
|
||
|
|
|
||
|
|
(b) The FSF's Back-Cover Text is:
|
||
|
|
|
||
|
|
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. -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Interoperation (Using the GNU Compiler Collection (GCC))</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Interoperation (Using the GNU Compiler Collection (GCC))">
|
||
|
|
<meta name="keywords" content="Interoperation (Using the GNU Compiler Collection (GCC))">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content="makeinfo">
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="Trouble.html#Trouble" rel="up" title="Trouble">
|
||
|
|
<link href="Incompatibilities.html#Incompatibilities" rel="next" title="Incompatibilities">
|
||
|
|
<link href="Actual-Bugs.html#Actual-Bugs" rel="prev" title="Actual Bugs">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smalllisp {margin-left: 3.2em}
|
||
|
|
kbd {font-style: oblique}
|
||
|
|
pre.display {font-family: inherit}
|
||
|
|
pre.format {font-family: inherit}
|
||
|
|
pre.menu-comment {font-family: serif}
|
||
|
|
pre.menu-preformatted {font-family: serif}
|
||
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smallexample {font-size: smaller}
|
||
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smalllisp {font-size: smaller}
|
||
|
|
span.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Interoperation"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Incompatibilities.html#Incompatibilities" accesskey="n" rel="next">Incompatibilities</a>, Previous: <a href="Actual-Bugs.html#Actual-Bugs" accesskey="p" rel="prev">Actual Bugs</a>, Up: <a href="Trouble.html#Trouble" accesskey="u" rel="up">Trouble</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Interoperation-1"></a>
|
||
|
|
<h3 class="section">13.2 Interoperation</h3>
|
||
|
|
|
||
|
|
<p>This section lists various difficulties encountered in using GCC
|
||
|
|
together with other compilers or with the assemblers, linkers,
|
||
|
|
libraries and debuggers on certain systems.
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> On many platforms, GCC supports a different ABI for C++ than do other
|
||
|
|
compilers, so the object files compiled by GCC cannot be used with object
|
||
|
|
files generated by another C++ compiler.
|
||
|
|
|
||
|
|
<p>An area where the difference is most apparent is name mangling. The use
|
||
|
|
of different name mangling is intentional, to protect you from more subtle
|
||
|
|
problems.
|
||
|
|
Compilers differ as to many internal details of C++ implementation,
|
||
|
|
including: how class instances are laid out, how multiple inheritance is
|
||
|
|
implemented, and how virtual function calls are handled. If the name
|
||
|
|
encoding were made the same, your programs would link against libraries
|
||
|
|
provided from other compilers—but the programs would then crash when
|
||
|
|
run. Incompatible libraries are then detected at link time, rather than
|
||
|
|
at run time.
|
||
|
|
</p>
|
||
|
|
</li><li> On some BSD systems, including some versions of Ultrix, use of profiling
|
||
|
|
causes static variable destructors (currently used only in C++) not to
|
||
|
|
be run.
|
||
|
|
|
||
|
|
</li><li> On a SPARC, GCC aligns all values of type <code>double</code> on an 8-byte
|
||
|
|
boundary, and it expects every <code>double</code> to be so aligned. The Sun
|
||
|
|
compiler usually gives <code>double</code> values 8-byte alignment, with one
|
||
|
|
exception: function arguments of type <code>double</code> may not be aligned.
|
||
|
|
|
||
|
|
<p>As a result, if a function compiled with Sun CC takes the address of an
|
||
|
|
argument of type <code>double</code> and passes this pointer of type
|
||
|
|
<code>double *</code> to a function compiled with GCC, dereferencing the
|
||
|
|
pointer may cause a fatal signal.
|
||
|
|
</p>
|
||
|
|
<p>One way to solve this problem is to compile your entire program with GCC.
|
||
|
|
Another solution is to modify the function that is compiled with
|
||
|
|
Sun CC to copy the argument into a local variable; local variables
|
||
|
|
are always properly aligned. A third solution is to modify the function
|
||
|
|
that uses the pointer to dereference it via the following function
|
||
|
|
<code>access_double</code> instead of directly with ‘<samp>*</samp>’:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">inline double
|
||
|
|
access_double (double *unaligned_ptr)
|
||
|
|
{
|
||
|
|
union d2i { double d; int i[2]; };
|
||
|
|
|
||
|
|
union d2i *p = (union d2i *) unaligned_ptr;
|
||
|
|
union d2i u;
|
||
|
|
|
||
|
|
u.i[0] = p->i[0];
|
||
|
|
u.i[1] = p->i[1];
|
||
|
|
|
||
|
|
return u.d;
|
||
|
|
}
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Storing into the pointer can be done likewise with the same union.
|
||
|
|
</p>
|
||
|
|
</li><li> On Solaris, the <code>malloc</code> function in the <samp>libmalloc.a</samp> library
|
||
|
|
may allocate memory that is only 4 byte aligned. Since GCC on the
|
||
|
|
SPARC assumes that doubles are 8 byte aligned, this may result in a
|
||
|
|
fatal signal if doubles are stored in memory allocated by the
|
||
|
|
<samp>libmalloc.a</samp> library.
|
||
|
|
|
||
|
|
<p>The solution is to not use the <samp>libmalloc.a</samp> library. Use instead
|
||
|
|
<code>malloc</code> and related functions from <samp>libc.a</samp>; they do not have
|
||
|
|
this problem.
|
||
|
|
</p>
|
||
|
|
</li><li> On the HP PA machine, ADB sometimes fails to work on functions compiled
|
||
|
|
with GCC. Specifically, it fails to work on functions that use
|
||
|
|
<code>alloca</code> or variable-size arrays. This is because GCC doesn’t
|
||
|
|
generate HP-UX unwind descriptors for such functions. It may even be
|
||
|
|
impossible to generate them.
|
||
|
|
|
||
|
|
</li><li> Debugging (<samp>-g</samp>) is not supported on the HP PA machine, unless you use
|
||
|
|
the preliminary GNU tools.
|
||
|
|
|
||
|
|
</li><li> Taking the address of a label may generate errors from the HP-UX
|
||
|
|
PA assembler. GAS for the PA does not have this problem.
|
||
|
|
|
||
|
|
</li><li> Using floating point parameters for indirect calls to static functions
|
||
|
|
will not work when using the HP assembler. There simply is no way for GCC
|
||
|
|
to specify what registers hold arguments for static functions when using
|
||
|
|
the HP assembler. GAS for the PA does not have this problem.
|
||
|
|
|
||
|
|
</li><li> In extremely rare cases involving some very large functions you may
|
||
|
|
receive errors from the HP linker complaining about an out of bounds
|
||
|
|
unconditional branch offset. This used to occur more often in previous
|
||
|
|
versions of GCC, but is now exceptionally rare. If you should run
|
||
|
|
into it, you can work around by making your function smaller.
|
||
|
|
|
||
|
|
</li><li> GCC compiled code sometimes emits warnings from the HP-UX assembler of
|
||
|
|
the form:
|
||
|
|
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(warning) Use of GR3 when
|
||
|
|
frame >= 8192 may cause conflict.
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>These warnings are harmless and can be safely ignored.
|
||
|
|
</p>
|
||
|
|
</li><li> In extremely rare cases involving some very large functions you may
|
||
|
|
receive errors from the AIX Assembler complaining about a displacement
|
||
|
|
that is too large. If you should run into it, you can work around by
|
||
|
|
making your function smaller.
|
||
|
|
|
||
|
|
</li><li> The <samp>libstdc++.a</samp> library in GCC relies on the SVR4 dynamic
|
||
|
|
linker semantics which merges global symbols between libraries and
|
||
|
|
applications, especially necessary for C++ streams functionality.
|
||
|
|
This is not the default behavior of AIX shared libraries and dynamic
|
||
|
|
linking. <samp>libstdc++.a</samp> is built on AIX with “runtime-linking”
|
||
|
|
enabled so that symbol merging can occur. To utilize this feature,
|
||
|
|
the application linked with <samp>libstdc++.a</samp> must include the
|
||
|
|
<samp>-Wl,-brtl</samp> flag on the link line. G++ cannot impose this
|
||
|
|
because this option may interfere with the semantics of the user
|
||
|
|
program and users may not always use ‘<samp>g++</samp>’ to link his or her
|
||
|
|
application. Applications are not required to use the
|
||
|
|
<samp>-Wl,-brtl</samp> flag on the link line—the rest of the
|
||
|
|
<samp>libstdc++.a</samp> library which is not dependent on the symbol
|
||
|
|
merging semantics will continue to function correctly.
|
||
|
|
|
||
|
|
</li><li> An application can interpose its own definition of functions for
|
||
|
|
functions invoked by <samp>libstdc++.a</samp> with “runtime-linking”
|
||
|
|
enabled on AIX. To accomplish this the application must be linked
|
||
|
|
with “runtime-linking” option and the functions explicitly must be
|
||
|
|
exported by the application (<samp>-Wl,-brtl,-bE:exportfile</samp>).
|
||
|
|
|
||
|
|
</li><li> AIX on the RS/6000 provides support (NLS) for environments outside of
|
||
|
|
the United States. Compilers and assemblers use NLS to support
|
||
|
|
locale-specific representations of various objects including
|
||
|
|
floating-point numbers (‘<samp>.</samp>’ vs ‘<samp>,</samp>’ for separating decimal
|
||
|
|
fractions). There have been problems reported where the library linked
|
||
|
|
with GCC does not produce the same floating-point formats that the
|
||
|
|
assembler accepts. If you have this problem, set the <code>LANG</code>
|
||
|
|
environment variable to ‘<samp>C</samp>’ or ‘<samp>En_US</samp>’.
|
||
|
|
|
||
|
|
</li><li> <a name="index-fdollars_002din_002didentifiers-1"></a>
|
||
|
|
Even if you specify <samp>-fdollars-in-identifiers</samp>,
|
||
|
|
you cannot successfully use ‘<samp>$</samp>’ in identifiers on the RS/6000 due
|
||
|
|
to a restriction in the IBM assembler. GAS supports these
|
||
|
|
identifiers.
|
||
|
|
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Incompatibilities.html#Incompatibilities" accesskey="n" rel="next">Incompatibilities</a>, Previous: <a href="Actual-Bugs.html#Actual-Bugs" accesskey="p" rel="prev">Actual Bugs</a>, Up: <a href="Trouble.html#Trouble" accesskey="u" rel="up">Trouble</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|