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diff --git a/share/doc/gcc/Interoperation.html b/share/doc/gcc/Interoperation.html new file mode 100644 index 0000000..01d9563 --- /dev/null +++ b/share/doc/gcc/Interoperation.html @@ -0,0 +1,236 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +Copyright (C) 1988-2023 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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Using the GNU Compiler Collection (GCC): Interoperation</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Interoperation"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Interoperation"> +<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="Indices.html#Indices" rel="index" title="Indices"> +<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="previous" title="Actual Bugs"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +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.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<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="previous">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="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Interoperation-1"></a> +<h3 class="section">14.2 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="previous">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="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |