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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gdb/Calling.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gdb/Calling.html b/share/doc/gdb/Calling.html new file mode 100644 index 0000000..99740dd --- /dev/null +++ b/share/doc/gdb/Calling.html @@ -0,0 +1,250 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- 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 "Free Software" and "Free Software Needs +Free Documentation", with the Front-Cover Texts being "A GNU Manual," +and with the Back-Cover Texts as in (a) below. + +(a) The FSF's Back-Cover Text is: "You are free to copy and modify +this GNU Manual. Buying copies from GNU Press supports the FSF in +developing GNU and promoting software freedom." --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Calling</title> + +<meta name="description" content="Debugging with GDB: Calling"> +<meta name="keywords" content="Debugging with GDB: Calling"> +<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="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Altering.html#Altering" rel="up" title="Altering"> +<link href="Patching.html#Patching" rel="next" title="Patching"> +<link href="Returning.html#Returning" rel="previous" title="Returning"> +<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" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Calling"></a> +<div class="header"> +<p> +Next: <a href="Patching.html#Patching" accesskey="n" rel="next">Patching</a>, Previous: <a href="Returning.html#Returning" accesskey="p" rel="previous">Returning</a>, Up: <a href="Altering.html#Altering" accesskey="u" rel="up">Altering</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> +</div> +<hr> +<a name="Calling-Program-Functions"></a> +<h3 class="section">17.5 Calling Program Functions</h3> + +<dl compact="compact"> +<dd><a name="index-calling-functions"></a> +<a name="index-inferior-functions_002c-calling"></a> +</dd> +<dt><code>print <var>expr</var></code></dt> +<dd><p>Evaluate the expression <var>expr</var> and display the resulting value. +The expression may include calls to functions in the program being +debugged. +</p> +<a name="index-call"></a> +</dd> +<dt><code>call <var>expr</var></code></dt> +<dd><p>Evaluate the expression <var>expr</var> without displaying <code>void</code> +returned values. +</p> +<p>You can use this variant of the <code>print</code> command if you want to +execute a function from your program that does not return anything +(a.k.a. <em>a void function</em>), but without cluttering the output +with <code>void</code> returned values that <small>GDB</small> will otherwise +print. If the result is not void, it is printed and saved in the +value history. +</p></dd> +</dl> + +<p>It is possible for the function you call via the <code>print</code> or +<code>call</code> command to generate a signal (e.g., if there’s a bug in +the function, or if you passed it incorrect arguments). What happens +in that case is controlled by the <code>set unwindonsignal</code> command. +</p> +<p>Similarly, with a C<tt>++</tt> program it is possible for the function you +call via the <code>print</code> or <code>call</code> command to generate an +exception that is not handled due to the constraints of the dummy +frame. In this case, any exception that is raised in the frame, but has +an out-of-frame exception handler will not be found. GDB builds a +dummy-frame for the inferior function call, and the unwinder cannot +seek for exception handlers outside of this dummy-frame. What happens +in that case is controlled by the +<code>set unwind-on-terminating-exception</code> command. +</p> +<dl compact="compact"> +<dt><code>set unwindonsignal</code></dt> +<dd><a name="index-set-unwindonsignal"></a> +<a name="index-unwind-stack-in-called-functions"></a> +<a name="index-call-dummy-stack-unwinding"></a> +<p>Set unwinding of the stack if a signal is received while in a function +that <small>GDB</small> called in the program being debugged. If set to on, +<small>GDB</small> unwinds the stack it created for the call and restores +the context to what it was before the call. If set to off (the +default), <small>GDB</small> stops in the frame where the signal was +received. +</p> +</dd> +<dt><code>show unwindonsignal</code></dt> +<dd><a name="index-show-unwindonsignal"></a> +<p>Show the current setting of stack unwinding in the functions called by +<small>GDB</small>. +</p> +</dd> +<dt><code>set unwind-on-terminating-exception</code></dt> +<dd><a name="index-set-unwind_002don_002dterminating_002dexception"></a> +<a name="index-unwind-stack-in-called-functions-with-unhandled-exceptions"></a> +<a name="index-call-dummy-stack-unwinding-on-unhandled-exception_002e"></a> +<p>Set unwinding of the stack if a C<tt>++</tt> exception is raised, but left +unhandled while in a function that <small>GDB</small> called in the program being +debugged. If set to on (the default), <small>GDB</small> unwinds the stack +it created for the call and restores the context to what it was before +the call. If set to off, <small>GDB</small> the exception is delivered to +the default C<tt>++</tt> exception handler and the inferior terminated. +</p> +</dd> +<dt><code>show unwind-on-terminating-exception</code></dt> +<dd><a name="index-show-unwind_002don_002dterminating_002dexception"></a> +<p>Show the current setting of stack unwinding in the functions called by +<small>GDB</small>. +</p> +</dd> +<dt><code>set may-call-functions</code></dt> +<dd><a name="index-set-may_002dcall_002dfunctions"></a> +<a name="index-disabling-calling-functions-in-the-program"></a> +<a name="index-calling-functions-in-the-program_002c-disabling"></a> +<p>Set permission to call functions in the program. +This controls whether <small>GDB</small> will attempt to call functions in +the program, such as with expressions in the <code>print</code> command. It +defaults to <code>on</code>. +</p> +<p>To call a function in the program, <small>GDB</small> has to temporarily +modify the state of the inferior. This has potentially undesired side +effects. Also, having <small>GDB</small> call nested functions is likely to +be erroneous and may even crash the program being debugged. You can +avoid such hazards by forbidding <small>GDB</small> from calling functions +in the program being debugged. If calling functions in the program +is forbidden, GDB will throw an error when a command (such as printing +an expression) starts a function call in the program. +</p> +</dd> +<dt><code>show may-call-functions</code></dt> +<dd><a name="index-show-may_002dcall_002dfunctions"></a> +<p>Show permission to call functions in the program. +</p> +</dd> +</dl> + +<a name="Calling-functions-with-no-debug-info"></a> +<h4 class="subsection">17.5.1 Calling functions with no debug info</h4> + +<a name="index-no-debug-info-functions"></a> +<p>Sometimes, a function you wish to call is missing debug information. +In such case, <small>GDB</small> does not know the type of the function, +including the types of the function’s parameters. To avoid calling +the inferior function incorrectly, which could result in the called +function functioning erroneously and even crash, <small>GDB</small> refuses +to call the function unless you tell it the type of the function. +</p> +<p>For prototyped (i.e. ANSI/ISO style) functions, there are two ways +to do that. The simplest is to cast the call to the function’s +declared return type. For example: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) p getenv ("PATH") +'getenv' has unknown return type; cast the call to its declared return type +(gdb) p (char *) getenv ("PATH") +$1 = 0x7fffffffe7ba "/usr/local/bin:/"... +</pre></div> + +<p>Casting the return type of a no-debug function is equivalent to +casting the function to a pointer to a prototyped function that has a +prototype that matches the types of the passed-in arguments, and +calling that. I.e., the call above is equivalent to: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) p ((char * (*) (const char *)) getenv) ("PATH") +</pre></div> + +<p>and given this prototyped C or C++ function with float parameters: +</p> +<div class="smallexample"> +<pre class="smallexample">float multiply (float v1, float v2) { return v1 * v2; } +</pre></div> + +<p>these calls are equivalent: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) p (float) multiply (2.0f, 3.0f) +(gdb) p ((float (*) (float, float)) multiply) (2.0f, 3.0f) +</pre></div> + +<p>If the function you wish to call is declared as unprototyped (i.e. +old K&R style), you must use the cast-to-function-pointer syntax, so +that <small>GDB</small> knows that it needs to apply default argument +promotions (promote float arguments to double). See <a href="ABI.html#ABI">float +promotion</a>. For example, given this unprototyped C function with +float parameters, and no debug info: +</p> +<div class="smallexample"> +<pre class="smallexample">float +multiply_noproto (v1, v2) + float v1, v2; +{ + return v1 * v2; +} +</pre></div> + +<p>you call it like this: +</p> +<div class="smallexample"> +<pre class="smallexample"> (gdb) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f) +</pre></div> + +<hr> +<div class="header"> +<p> +Next: <a href="Patching.html#Patching" accesskey="n" rel="next">Patching</a>, Previous: <a href="Returning.html#Returning" accesskey="p" rel="previous">Returning</a>, Up: <a href="Altering.html#Altering" accesskey="u" rel="up">Altering</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> +</div> + + + +</body> +</html> |