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diff --git a/share/doc/stabs/Procedures.html b/share/doc/stabs/Procedures.html new file mode 100644 index 0000000..80f4983 --- /dev/null +++ b/share/doc/stabs/Procedures.html @@ -0,0 +1,187 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1992-2023 Free Software Foundation, Inc. +Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, +and David MacKenzie. + +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 no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled "GNU +Free Documentation License". --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>STABS: Procedures</title> + +<meta name="description" content="STABS: Procedures"> +<meta name="keywords" content="STABS: Procedures"> +<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="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Program-Structure.html#Program-Structure" rel="up" title="Program Structure"> +<link href="Nested-Procedures.html#Nested-Procedures" rel="next" title="Nested Procedures"> +<link href="Line-Numbers.html#Line-Numbers" rel="previous" title="Line Numbers"> +<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="Procedures"></a> +<div class="header"> +<p> +Next: <a href="Nested-Procedures.html#Nested-Procedures" accesskey="n" rel="next">Nested Procedures</a>, Previous: <a href="Line-Numbers.html#Line-Numbers" accesskey="p" rel="previous">Line Numbers</a>, Up: <a href="Program-Structure.html#Program-Structure" accesskey="u" rel="up">Program Structure</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Procedures-1"></a> +<h3 class="section">2.5 Procedures</h3> + +<a name="index-N_005fFUN_002c-for-functions"></a> +<a name="index-N_005fFNAME"></a> +<a name="index-N_005fSTSYM_002c-for-functions-_0028Sun-acc_0029"></a> +<a name="index-N_005fGSYM_002c-for-functions-_0028Sun-acc_0029"></a> +<p>All of the following stabs normally use the <code>N_FUN</code> symbol type. +However, Sun’s <code>acc</code> compiler on SunOS4 uses <code>N_GSYM</code> and +<code>N_STSYM</code>, which means that the value of the stab for the function +is useless and the debugger must get the address of the function from +the non-stab symbols instead. On systems where non-stab symbols have +leading underscores, the stabs will lack underscores and the debugger +needs to know about the leading underscore to match up the stab and the +non-stab symbol. BSD Fortran is said to use <code>N_FNAME</code> with the +same restriction; the value of the symbol is not useful (I’m not sure it +really does use this, because GDB doesn’t handle this and no one has +complained). +</p> +<a name="index-C_005fFUN"></a> +<p>A function is represented by an ‘<samp>F</samp>’ symbol descriptor for a global +(extern) function, and ‘<samp>f</samp>’ for a static (local) function. For +a.out, the value of the symbol is the address of the start of the +function; it is already relocated. For stabs in ELF, the SunPRO +compiler version 2.0.1 and GCC put out an address which gets relocated +by the linker. In a future release SunPRO is planning to put out zero, +in which case the address can be found from the ELF (non-stab) symbol. +Because looking things up in the ELF symbols would probably be slow, I’m +not sure how to find which symbol of that name is the right one, and +this doesn’t provide any way to deal with nested functions, it would +probably be better to make the value of the stab an address relative to +the start of the file, or just absolute. See <a href="ELF-Linker-Relocation.html#ELF-Linker-Relocation">ELF Linker Relocation</a> for more information on linker relocation of stabs in ELF +files. For XCOFF, the stab uses the <code>C_FUN</code> storage class and the +value of the stab is meaningless; the address of the function can be +found from the csect symbol (XTY_LD/XMC_PR). +</p> +<p>The type information of the stab represents the return type of the +function; thus ‘<samp>foo:f5</samp>’ means that foo is a function returning type +5. There is no need to try to get the line number of the start of the +function from the stab for the function; it is in the next +<code>N_SLINE</code> symbol. +</p> +<p>Some compilers (such as Sun’s Solaris compiler) support an extension for +specifying the types of the arguments. I suspect this extension is not +used for old (non-prototyped) function definitions in C. If the +extension is in use, the type information of the stab for the function +is followed by type information for each argument, with each argument +preceded by ‘<samp>;</samp>’. An argument type of 0 means that additional +arguments are being passed, whose types and number may vary (‘<samp>...</samp>’ +in ANSI C). GDB has tolerated this extension (parsed the syntax, if not +necessarily used the information) since at least version 4.8; I don’t +know whether all versions of dbx tolerate it. The argument types given +here are not redundant with the symbols for the formal parameters +(see <a href="Parameters.html#Parameters">Parameters</a>); they are the types of the arguments as they are +passed, before any conversions might take place. For example, if a C +function which is declared without a prototype takes a <code>float</code> +argument, the value is passed as a <code>double</code> but then converted to a +<code>float</code>. Debuggers need to use the types given in the arguments +when printing values, but when calling the function they need to use the +types given in the symbol defining the function. +</p> +<p>If the return type and types of arguments of a function which is defined +in another source file are specified (i.e., a function prototype in ANSI +C), traditionally compilers emit no stab; the only way for the debugger +to find the information is if the source file where the function is +defined was also compiled with debugging symbols. As an extension the +Solaris compiler uses symbol descriptor ‘<samp>P</samp>’ followed by the return +type of the function, followed by the arguments, each preceded by +‘<samp>;</samp>’, as in a stab with symbol descriptor ‘<samp>f</samp>’ or ‘<samp>F</samp>’. +This use of symbol descriptor ‘<samp>P</samp>’ can be distinguished from its use +for register parameters (see <a href="Register-Parameters.html#Register-Parameters">Register Parameters</a>) by the fact that it has +symbol type <code>N_FUN</code>. +</p> +<p>The AIX documentation also defines symbol descriptor ‘<samp>J</samp>’ as an +internal function. I assume this means a function nested within another +function. It also says symbol descriptor ‘<samp>m</samp>’ is a module in +Modula-2 or extended Pascal. +</p> +<p>Procedures (functions which do not return values) are represented as +functions returning the <code>void</code> type in C. I don’t see why this couldn’t +be used for all languages (inventing a <code>void</code> type for this purpose if +necessary), but the AIX documentation defines ‘<samp>I</samp>’, ‘<samp>P</samp>’, and +‘<samp>Q</samp>’ for internal, global, and static procedures, respectively. +These symbol descriptors are unusual in that they are not followed by +type information. +</p> +<p>The following example shows a stab for a function <code>main</code> which +returns type number <code>1</code>. The <code>_main</code> specified for the value +is a reference to an assembler label which is used to fill in the start +address of the function. +</p> +<div class="example"> +<pre class="example">.stabs "main:F1",36,0,0,_main # <span class="roman">36 is N_FUN</span> +</pre></div> + +<p>The stab representing a procedure is located immediately following the +code of the procedure. This stab is in turn directly followed by a +group of other stabs describing elements of the procedure. These other +stabs describe the procedure’s parameters, its block local variables, and +its block structure. +</p> +<p>If functions can appear in different sections, then the debugger may not +be able to find the end of a function. Recent versions of GCC will mark +the end of a function with an <code>N_FUN</code> symbol with an empty string +for the name. The value is the address of the end of the current +function. Without such a symbol, there is no indication of the address +of the end of a function, and you must assume that it ended at the +starting address of the next function or at the end of the text section +for the program. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Nested-Procedures.html#Nested-Procedures" accesskey="n" rel="next">Nested Procedures</a>, Previous: <a href="Line-Numbers.html#Line-Numbers" accesskey="p" rel="previous">Line Numbers</a>, Up: <a href="Program-Structure.html#Program-Structure" accesskey="u" rel="up">Program Structure</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |