<html lang="en">
<head>
<title>Warnings and Errors - Using the GNU Compiler Collection (GCC)</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Trouble.html#Trouble" title="Trouble">
<link rel="prev" href="Non_002dbugs.html#Non_002dbugs" title="Non-bugs">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
2008 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 1.2 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>
<link rel="stylesheet" type="text/css" href="../cs.css">
</head>
<body>
<div class="node">
<a name="Warnings-and-Errors"></a>
<p>
Previous:&nbsp;<a rel="previous" accesskey="p" href="Non_002dbugs.html#Non_002dbugs">Non-bugs</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Trouble.html#Trouble">Trouble</a>
<hr>
</div>

<h3 class="section">11.10 Warning Messages and Error Messages</h3>

<p><a name="index-error-messages-3250"></a><a name="index-warnings-vs-errors-3251"></a><a name="index-messages_002c-warning-and-error-3252"></a>The GNU compiler can produce two kinds of diagnostics: errors and
warnings.  Each kind has a different purpose:

     <ul>
<li><dfn>Errors</dfn> report problems that make it impossible to compile your
program.  GCC reports errors with the source file name and line
number where the problem is apparent.

     <li><dfn>Warnings</dfn> report other unusual conditions in your code that
<em>may</em> indicate a problem, although compilation can (and does)
proceed.  Warning messages also report the source file name and line
number, but include the text &lsquo;<samp><span class="samp">warning:</span></samp>&rsquo; to distinguish them
from error messages. 
</ul>

 <p>Warnings may indicate danger points where you should check to make sure
that your program really does what you intend; or the use of obsolete
features; or the use of nonstandard features of GNU C or C++.  Many
warnings are issued only if you ask for them, with one of the <samp><span class="option">-W</span></samp>
options (for instance, <samp><span class="option">-Wall</span></samp> requests a variety of useful
warnings).

 <p><a name="index-pedantic-3253"></a><a name="index-pedantic_002derrors-3254"></a>GCC always tries to compile your program if possible; it never
gratuitously rejects a program whose meaning is clear merely because
(for instance) it fails to conform to a standard.  In some cases,
however, the C and C++ standards specify that certain extensions are
forbidden, and a diagnostic <em>must</em> be issued by a conforming
compiler.  The <samp><span class="option">-pedantic</span></samp> option tells GCC to issue warnings in
such cases; <samp><span class="option">-pedantic-errors</span></samp> says to make them errors instead. 
This does not mean that <em>all</em> non-ISO constructs get warnings
or errors.

 <p>See <a href="Warning-Options.html#Warning-Options">Options to Request or Suppress Warnings</a>, for
more detail on these and related command-line options.

<!-- Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -->
<!-- 1999, 2000, 2001, 2003, 2004, 2007 Free Software Foundation, Inc. -->
<!-- This is part of the GCC manual. -->
<!-- For copying conditions, see the file gcc.texi. -->
 </body></html>