1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. 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You must call this subroutine explicitly in your 83program’s startup code. 84</p> 85</dd> 86<dt><code>handle_exception</code></dt> 87<dd><a name="index-handle_005fexception"></a> 88<a name="index-remote-serial-stub_002c-main-routine"></a> 89<p>This is the central workhorse, but your program never calls it 90explicitly—the setup code arranges for <code>handle_exception</code> to 91run when a trap is triggered. 92</p> 93<p><code>handle_exception</code> takes control when your program stops during 94execution (for example, on a breakpoint), and mediates communications 95with <small>GDB</small> on the host machine. This is where the communications 96protocol is implemented; <code>handle_exception</code> acts as the <small>GDB</small> 97representative on the target machine. It begins by sending summary 98information on the state of your program, then continues to execute, 99retrieving and transmitting any information <small>GDB</small> needs, until you 100execute a <small>GDB</small> command that makes your program resume; at that point, 101<code>handle_exception</code> returns control to your own code on the target 102machine. 103</p> 104</dd> 105<dt><code>breakpoint</code></dt> 106<dd><a name="index-breakpoint-subroutine_002c-remote"></a> 107<p>Use this auxiliary subroutine to make your program contain a 108breakpoint. Depending on the particular situation, this may be the only 109way for <small>GDB</small> to get control. For instance, if your target 110machine has some sort of interrupt button, you won’t need to call this; 111pressing the interrupt button transfers control to 112<code>handle_exception</code>—in effect, to <small>GDB</small>. On some machines, 113simply receiving characters on the serial port may also trigger a trap; 114again, in that situation, you don’t need to call <code>breakpoint</code> from 115your own program—simply running ‘<samp>target remote</samp>’ from the host 116<small>GDB</small> session gets control. 117</p> 118<p>Call <code>breakpoint</code> if none of these is true, or if you simply want 119to make certain your program stops at a predetermined point for the 120start of your debugging session. 121</p></dd> 122</dl> 123 124<hr> 125<div class="header"> 126<p> 127Next: <a href="Bootstrapping.html#Bootstrapping" accesskey="n" rel="next">Bootstrapping</a>, Up: <a href="Remote-Stub.html#Remote-Stub" accesskey="u" rel="up">Remote Stub</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> 128</div> 129 130 131 132</body> 133</html> 134