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.
196 lines
10 KiB
HTML
196 lines
10 KiB
HTML
4 years ago
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Exception Handling - GNU Compiler Collection (GCC) Internals</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals">
|
||
|
|
<meta name="generator" content="makeinfo 4.13">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Stack-and-Calling.html#Stack-and-Calling" title="Stack and Calling">
|
||
|
|
<link rel="prev" href="Frame-Layout.html#Frame-Layout" title="Frame Layout">
|
||
|
|
<link rel="next" href="Stack-Checking.html#Stack-Checking" title="Stack Checking">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
Copyright (C) 1988-2015 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.-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family:serif; font-weight:normal; }
|
||
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<a name="Exception-Handling"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="Stack-Checking.html#Stack-Checking">Stack Checking</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Frame-Layout.html#Frame-Layout">Frame Layout</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Stack-and-Calling.html#Stack-and-Calling">Stack and Calling</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">17.9.2 Exception Handling Support</h4>
|
||
|
|
|
||
|
|
<p><a name="index-exception-handling-4169"></a>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>EH_RETURN_DATA_REGNO</b> (<var>N</var>)<var><a name="index-EH_005fRETURN_005fDATA_005fREGNO-4170"></a></var><br>
|
||
|
|
<blockquote><p>A C expression whose value is the <var>N</var>th register number used for
|
||
|
|
data by exception handlers, or <code>INVALID_REGNUM</code> if fewer than
|
||
|
|
<var>N</var> registers are usable.
|
||
|
|
|
||
|
|
<p>The exception handling library routines communicate with the exception
|
||
|
|
handlers via a set of agreed upon registers. Ideally these registers
|
||
|
|
should be call-clobbered; it is possible to use call-saved registers,
|
||
|
|
but may negatively impact code size. The target must support at least
|
||
|
|
2 data registers, but should define 4 if there are enough free registers.
|
||
|
|
|
||
|
|
<p>You must define this macro if you want to support call frame exception
|
||
|
|
handling like that provided by DWARF 2.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>EH_RETURN_STACKADJ_RTX</b><var><a name="index-EH_005fRETURN_005fSTACKADJ_005fRTX-4171"></a></var><br>
|
||
|
|
<blockquote><p>A C expression whose value is RTL representing a location in which
|
||
|
|
to store a stack adjustment to be applied before function return.
|
||
|
|
This is used to unwind the stack to an exception handler's call frame.
|
||
|
|
It will be assigned zero on code paths that return normally.
|
||
|
|
|
||
|
|
<p>Typically this is a call-clobbered hard register that is otherwise
|
||
|
|
untouched by the epilogue, but could also be a stack slot.
|
||
|
|
|
||
|
|
<p>Do not define this macro if the stack pointer is saved and restored
|
||
|
|
by the regular prolog and epilog code in the call frame itself; in
|
||
|
|
this case, the exception handling library routines will update the
|
||
|
|
stack location to be restored in place. Otherwise, you must define
|
||
|
|
this macro if you want to support call frame exception handling like
|
||
|
|
that provided by DWARF 2.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>EH_RETURN_HANDLER_RTX</b><var><a name="index-EH_005fRETURN_005fHANDLER_005fRTX-4172"></a></var><br>
|
||
|
|
<blockquote><p>A C expression whose value is RTL representing a location in which
|
||
|
|
to store the address of an exception handler to which we should
|
||
|
|
return. It will not be assigned on code paths that return normally.
|
||
|
|
|
||
|
|
<p>Typically this is the location in the call frame at which the normal
|
||
|
|
return address is stored. For targets that return by popping an
|
||
|
|
address off the stack, this might be a memory address just below
|
||
|
|
the <em>target</em> call frame rather than inside the current call
|
||
|
|
frame. If defined, <code>EH_RETURN_STACKADJ_RTX</code> will have already
|
||
|
|
been assigned, so it may be used to calculate the location of the
|
||
|
|
target call frame.
|
||
|
|
|
||
|
|
<p>Some targets have more complex requirements than storing to an
|
||
|
|
address calculable during initial code generation. In that case
|
||
|
|
the <code>eh_return</code> instruction pattern should be used instead.
|
||
|
|
|
||
|
|
<p>If you want to support call frame exception handling, you must
|
||
|
|
define either this macro or the <code>eh_return</code> instruction pattern.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>RETURN_ADDR_OFFSET</b><var><a name="index-RETURN_005fADDR_005fOFFSET-4173"></a></var><br>
|
||
|
|
<blockquote><p>If defined, an integer-valued C expression for which rtl will be generated
|
||
|
|
to add it to the exception handler address before it is searched in the
|
||
|
|
exception handling tables, and to subtract it again from the address before
|
||
|
|
using it to return to the exception handler.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_PREFERRED_EH_DATA_FORMAT</b> (<var>code, global</var>)<var><a name="index-ASM_005fPREFERRED_005fEH_005fDATA_005fFORMAT-4174"></a></var><br>
|
||
|
|
<blockquote><p>This macro chooses the encoding of pointers embedded in the exception
|
||
|
|
handling sections. If at all possible, this should be defined such
|
||
|
|
that the exception handling section will not require dynamic relocations,
|
||
|
|
and so may be read-only.
|
||
|
|
|
||
|
|
<p><var>code</var> is 0 for data, 1 for code labels, 2 for function pointers.
|
||
|
|
<var>global</var> is true if the symbol may be affected by dynamic relocations.
|
||
|
|
The macro should return a combination of the <code>DW_EH_PE_*</code> defines
|
||
|
|
as found in <samp><span class="file">dwarf2.h</span></samp>.
|
||
|
|
|
||
|
|
<p>If this macro is not defined, pointers will not be encoded but
|
||
|
|
represented directly.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX</b> (<var>file, encoding, size, addr, done</var>)<var><a name="index-ASM_005fMAYBE_005fOUTPUT_005fENCODED_005fADDR_005fRTX-4175"></a></var><br>
|
||
|
|
<blockquote><p>This macro allows the target to emit whatever special magic is required
|
||
|
|
to represent the encoding chosen by <code>ASM_PREFERRED_EH_DATA_FORMAT</code>.
|
||
|
|
Generic code takes care of pc-relative and indirect encodings; this must
|
||
|
|
be defined if the target uses text-relative or data-relative encodings.
|
||
|
|
|
||
|
|
<p>This is a C statement that branches to <var>done</var> if the format was
|
||
|
|
handled. <var>encoding</var> is the format chosen, <var>size</var> is the number
|
||
|
|
of bytes that the format occupies, <var>addr</var> is the <code>SYMBOL_REF</code>
|
||
|
|
to be emitted.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>MD_FALLBACK_FRAME_STATE_FOR</b> (<var>context, fs</var>)<var><a name="index-MD_005fFALLBACK_005fFRAME_005fSTATE_005fFOR-4176"></a></var><br>
|
||
|
|
<blockquote><p>This macro allows the target to add CPU and operating system specific
|
||
|
|
code to the call-frame unwinder for use when there is no unwind data
|
||
|
|
available. The most common reason to implement this macro is to unwind
|
||
|
|
through signal frames.
|
||
|
|
|
||
|
|
<p>This macro is called from <code>uw_frame_state_for</code> in
|
||
|
|
<samp><span class="file">unwind-dw2.c</span></samp>, <samp><span class="file">unwind-dw2-xtensa.c</span></samp> and
|
||
|
|
<samp><span class="file">unwind-ia64.c</span></samp>. <var>context</var> is an <code>_Unwind_Context</code>;
|
||
|
|
<var>fs</var> is an <code>_Unwind_FrameState</code>. Examine <code>context->ra</code>
|
||
|
|
for the address of the code being executed and <code>context->cfa</code> for
|
||
|
|
the stack pointer value. If the frame can be decoded, the register
|
||
|
|
save addresses should be updated in <var>fs</var> and the macro should
|
||
|
|
evaluate to <code>_URC_NO_REASON</code>. If the frame cannot be decoded,
|
||
|
|
the macro should evaluate to <code>_URC_END_OF_STACK</code>.
|
||
|
|
|
||
|
|
<p>For proper signal handling in Java this macro is accompanied by
|
||
|
|
<code>MAKE_THROW_FRAME</code>, defined in <samp><span class="file">libjava/include/*-signal.h</span></samp> headers.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>MD_HANDLE_UNWABI</b> (<var>context, fs</var>)<var><a name="index-MD_005fHANDLE_005fUNWABI-4177"></a></var><br>
|
||
|
|
<blockquote><p>This macro allows the target to add operating system specific code to the
|
||
|
|
call-frame unwinder to handle the IA-64 <code>.unwabi</code> unwinding directive,
|
||
|
|
usually used for signal or interrupt frames.
|
||
|
|
|
||
|
|
<p>This macro is called from <code>uw_update_context</code> in libgcc's
|
||
|
|
<samp><span class="file">unwind-ia64.c</span></samp>. <var>context</var> is an <code>_Unwind_Context</code>;
|
||
|
|
<var>fs</var> is an <code>_Unwind_FrameState</code>. Examine <code>fs->unwabi</code>
|
||
|
|
for the abi and context in the <code>.unwabi</code> directive. If the
|
||
|
|
<code>.unwabi</code> directive can be handled, the register save addresses should
|
||
|
|
be updated in <var>fs</var>.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>TARGET_USES_WEAK_UNWIND_INFO</b><var><a name="index-TARGET_005fUSES_005fWEAK_005fUNWIND_005fINFO-4178"></a></var><br>
|
||
|
|
<blockquote><p>A C expression that evaluates to true if the target requires unwind
|
||
|
|
info to be given comdat linkage. Define it to be <code>1</code> if comdat
|
||
|
|
linkage is necessary. The default is <code>0</code>.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|