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<title>Diagnostic Message Formatting Options (Using the GNU Compiler Collection (GCC))</title>
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<a name="Diagnostic-Message-Formatting-Options"></a>
<div class="header">
<p>
Next: <a href="Warning-Options.html#Warning-Options" accesskey="n" rel="next">Warning Options</a>, Previous: <a href="Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options.html#Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options" accesskey="p" rel="prev">Objective-C and Objective-C++ Dialect Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Options-to-Control-Diagnostic-Messages-Formatting"></a>
<h3 class="section">3.7 Options to Control Diagnostic Messages Formatting</h3>
<a name="index-options-to-control-diagnostics-formatting"></a>
<a name="index-diagnostic-messages"></a>
<a name="index-message-formatting"></a>
<p>Traditionally, diagnostic messages have been formatted irrespective of
the output device&rsquo;s aspect (e.g. its width, &hellip;). You can use the
options described below
to control the formatting algorithm for diagnostic messages,
e.g. how many characters per line, how often source location
information should be reported. Note that some language front ends may not
honor these options.
</p>
<dl compact="compact">
<dt><code>-fmessage-length=<var>n</var></code></dt>
<dd><a name="index-fmessage_002dlength"></a>
<p>Try to format error messages so that they fit on lines of about
<var>n</var> characters. If <var>n</var> is zero, then no line-wrapping is
done; each error message appears on a single line. This is the
default for all front ends.
</p>
</dd>
<dt><code>-fdiagnostics-show-location=once</code></dt>
<dd><a name="index-fdiagnostics_002dshow_002dlocation"></a>
<p>Only meaningful in line-wrapping mode. Instructs the diagnostic messages
reporter to emit source location information <em>once</em>; that is, in
case the message is too long to fit on a single physical line and has to
be wrapped, the source location won&rsquo;t be emitted (as prefix) again,
over and over, in subsequent continuation lines. This is the default
behavior.
</p>
</dd>
<dt><code>-fdiagnostics-show-location=every-line</code></dt>
<dd><p>Only meaningful in line-wrapping mode. Instructs the diagnostic
messages reporter to emit the same source location information (as
prefix) for physical lines that result from the process of breaking
a message which is too long to fit on a single line.
</p>
</dd>
<dt><code>-fdiagnostics-color[=<var>WHEN</var>]</code></dt>
<dt><code>-fno-diagnostics-color</code></dt>
<dd><a name="index-fdiagnostics_002dcolor"></a>
<a name="index-highlight_002c-color"></a>
<a name="index-GCC_005fCOLORS-environment-variable"></a>
<p>Use color in diagnostics. <var>WHEN</var> is &lsquo;<samp>never</samp>&rsquo;, &lsquo;<samp>always</samp>&rsquo;,
or &lsquo;<samp>auto</samp>&rsquo;. The default depends on how the compiler has been configured,
it can be any of the above <var>WHEN</var> options or also &lsquo;<samp>never</samp>&rsquo;
if <code>GCC_COLORS</code> environment variable isn&rsquo;t present in the environment,
and &lsquo;<samp>auto</samp>&rsquo; otherwise.
&lsquo;<samp>auto</samp>&rsquo; means to use color only when the standard error is a terminal.
The forms <samp>-fdiagnostics-color</samp> and <samp>-fno-diagnostics-color</samp> are
aliases for <samp>-fdiagnostics-color=always</samp> and
<samp>-fdiagnostics-color=never</samp>, respectively.
</p>
<p>The colors are defined by the environment variable <code>GCC_COLORS</code>.
Its value is a colon-separated list of capabilities and Select Graphic
Rendition (SGR) substrings. SGR commands are interpreted by the
terminal or terminal emulator. (See the section in the documentation
of your text terminal for permitted values and their meanings as
character attributes.) These substring values are integers in decimal
representation and can be concatenated with semicolons.
Common values to concatenate include
&lsquo;<samp>1</samp>&rsquo; for bold,
&lsquo;<samp>4</samp>&rsquo; for underline,
&lsquo;<samp>5</samp>&rsquo; for blink,
&lsquo;<samp>7</samp>&rsquo; for inverse,
&lsquo;<samp>39</samp>&rsquo; for default foreground color,
&lsquo;<samp>30</samp>&rsquo; to &lsquo;<samp>37</samp>&rsquo; for foreground colors,
&lsquo;<samp>90</samp>&rsquo; to &lsquo;<samp>97</samp>&rsquo; for 16-color mode foreground colors,
&lsquo;<samp>38;5;0</samp>&rsquo; to &lsquo;<samp>38;5;255</samp>&rsquo;
for 88-color and 256-color modes foreground colors,
&lsquo;<samp>49</samp>&rsquo; for default background color,
&lsquo;<samp>40</samp>&rsquo; to &lsquo;<samp>47</samp>&rsquo; for background colors,
&lsquo;<samp>100</samp>&rsquo; to &lsquo;<samp>107</samp>&rsquo; for 16-color mode background colors,
and &lsquo;<samp>48;5;0</samp>&rsquo; to &lsquo;<samp>48;5;255</samp>&rsquo;
for 88-color and 256-color modes background colors.
</p>
<p>The default <code>GCC_COLORS</code> is
</p><div class="smallexample">
<pre class="smallexample">error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
quote=01:fixit-insert=32:fixit-delete=31:\
diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
type-diff=01;32
</pre></div>
<p>where &lsquo;<samp>01;31</samp>&rsquo; is bold red, &lsquo;<samp>01;35</samp>&rsquo; is bold magenta,
&lsquo;<samp>01;36</samp>&rsquo; is bold cyan, &lsquo;<samp>32</samp>&rsquo; is green, &lsquo;<samp>34</samp>&rsquo; is blue,
&lsquo;<samp>01</samp>&rsquo; is bold, and &lsquo;<samp>31</samp>&rsquo; is red.
Setting <code>GCC_COLORS</code> to the empty string disables colors.
Supported capabilities are as follows.
</p>
<dl compact="compact">
<dt><code>error=</code></dt>
<dd><a name="index-error-GCC_005fCOLORS-capability"></a>
<p>SGR substring for error: markers.
</p>
</dd>
<dt><code>warning=</code></dt>
<dd><a name="index-warning-GCC_005fCOLORS-capability"></a>
<p>SGR substring for warning: markers.
</p>
</dd>
<dt><code>note=</code></dt>
<dd><a name="index-note-GCC_005fCOLORS-capability"></a>
<p>SGR substring for note: markers.
</p>
</dd>
<dt><code>range1=</code></dt>
<dd><a name="index-range1-GCC_005fCOLORS-capability"></a>
<p>SGR substring for first additional range.
</p>
</dd>
<dt><code>range2=</code></dt>
<dd><a name="index-range2-GCC_005fCOLORS-capability"></a>
<p>SGR substring for second additional range.
</p>
</dd>
<dt><code>locus=</code></dt>
<dd><a name="index-locus-GCC_005fCOLORS-capability"></a>
<p>SGR substring for location information, &lsquo;<samp>file:line</samp>&rsquo; or
&lsquo;<samp>file:line:column</samp>&rsquo; etc.
</p>
</dd>
<dt><code>quote=</code></dt>
<dd><a name="index-quote-GCC_005fCOLORS-capability"></a>
<p>SGR substring for information printed within quotes.
</p>
</dd>
<dt><code>fixit-insert=</code></dt>
<dd><a name="index-fixit_002dinsert-GCC_005fCOLORS-capability"></a>
<p>SGR substring for fix-it hints suggesting text to
be inserted or replaced.
</p>
</dd>
<dt><code>fixit-delete=</code></dt>
<dd><a name="index-fixit_002ddelete-GCC_005fCOLORS-capability"></a>
<p>SGR substring for fix-it hints suggesting text to
be deleted.
</p>
</dd>
<dt><code>diff-filename=</code></dt>
<dd><a name="index-diff_002dfilename-GCC_005fCOLORS-capability"></a>
<p>SGR substring for filename headers within generated patches.
</p>
</dd>
<dt><code>diff-hunk=</code></dt>
<dd><a name="index-diff_002dhunk-GCC_005fCOLORS-capability"></a>
<p>SGR substring for the starts of hunks within generated patches.
</p>
</dd>
<dt><code>diff-delete=</code></dt>
<dd><a name="index-diff_002ddelete-GCC_005fCOLORS-capability"></a>
<p>SGR substring for deleted lines within generated patches.
</p>
</dd>
<dt><code>diff-insert=</code></dt>
<dd><a name="index-diff_002dinsert-GCC_005fCOLORS-capability"></a>
<p>SGR substring for inserted lines within generated patches.
</p>
</dd>
<dt><code>type-diff=</code></dt>
<dd><a name="index-type_002ddiff-GCC_005fCOLORS-capability"></a>
<p>SGR substring for highlighting mismatching types within template
arguments in the C++ frontend.
</p></dd>
</dl>
</dd>
<dt><code>-fno-diagnostics-show-option</code></dt>
<dd><a name="index-fno_002ddiagnostics_002dshow_002doption"></a>
<a name="index-fdiagnostics_002dshow_002doption"></a>
<p>By default, each diagnostic emitted includes text indicating the
command-line option that directly controls the diagnostic (if such an
option is known to the diagnostic machinery). Specifying the
<samp>-fno-diagnostics-show-option</samp> flag suppresses that behavior.
</p>
</dd>
<dt><code>-fno-diagnostics-show-caret</code></dt>
<dd><a name="index-fno_002ddiagnostics_002dshow_002dcaret"></a>
<a name="index-fdiagnostics_002dshow_002dcaret"></a>
<p>By default, each diagnostic emitted includes the original source line
and a caret &lsquo;<samp>^</samp>&rsquo; indicating the column. This option suppresses this
information. The source line is truncated to <var>n</var> characters, if
the <samp>-fmessage-length=n</samp> option is given. When the output is done
to the terminal, the width is limited to the width given by the
<code>COLUMNS</code> environment variable or, if not set, to the terminal width.
</p>
</dd>
<dt><code>-fdiagnostics-parseable-fixits</code></dt>
<dd><a name="index-fdiagnostics_002dparseable_002dfixits"></a>
<p>Emit fix-it hints in a machine-parseable format, suitable for consumption
by IDEs. For each fix-it, a line will be printed after the relevant
diagnostic, starting with the string &ldquo;fix-it:&rdquo;. For example:
</p>
<div class="smallexample">
<pre class="smallexample">fix-it:&quot;test.c&quot;:{45:3-45:21}:&quot;gtk_widget_show_all&quot;
</pre></div>
<p>The location is expressed as a half-open range, expressed as a count of
bytes, starting at byte 1 for the initial column. In the above example,
bytes 3 through 20 of line 45 of &ldquo;test.c&rdquo; are to be replaced with the
given string:
</p>
<div class="smallexample">
<pre class="smallexample">00000000011111111112222222222
12345678901234567890123456789
gtk_widget_showall (dlg);
^^^^^^^^^^^^^^^^^^
gtk_widget_show_all
</pre></div>
<p>The filename and replacement string escape backslash as &ldquo;\\&quot;, tab as &ldquo;\t&rdquo;,
newline as &ldquo;\n&rdquo;, double quotes as &ldquo;\&quot;&rdquo;, non-printable characters as octal
(e.g. vertical tab as &ldquo;\013&rdquo;).
</p>
<p>An empty replacement string indicates that the given range is to be removed.
An empty range (e.g. &ldquo;45:3-45:3&rdquo;) indicates that the string is to
be inserted at the given position.
</p>
</dd>
<dt><code>-fdiagnostics-generate-patch</code></dt>
<dd><a name="index-fdiagnostics_002dgenerate_002dpatch"></a>
<p>Print fix-it hints to stderr in unified diff format, after any diagnostics
are printed. For example:
</p>
<div class="smallexample">
<pre class="smallexample">--- test.c
+++ test.c
@ -42,5 +42,5 @
void show_cb(GtkDialog *dlg)
{
- gtk_widget_showall(dlg);
+ gtk_widget_show_all(dlg);
}
</pre></div>
<p>The diff may or may not be colorized, following the same rules
as for diagnostics (see <samp>-fdiagnostics-color</samp>).
</p>
</dd>
<dt><code>-fdiagnostics-show-template-tree</code></dt>
<dd><a name="index-fdiagnostics_002dshow_002dtemplate_002dtree"></a>
<p>In the C++ frontend, when printing diagnostics showing mismatching
template types, such as:
</p>
<div class="smallexample">
<pre class="smallexample"> could not convert 'std::map&lt;int, std::vector&lt;double&gt; &gt;()'
from 'map&lt;[...],vector&lt;double&gt;&gt;' to 'map&lt;[...],vector&lt;float&gt;&gt;
</pre></div>
<p>the <samp>-fdiagnostics-show-template-tree</samp> flag enables printing a
tree-like structure showing the common and differing parts of the types,
such as:
</p>
<div class="smallexample">
<pre class="smallexample"> map&lt;
[...],
vector&lt;
[double != float]&gt;&gt;
</pre></div>
<p>The parts that differ are highlighted with color (&ldquo;double&rdquo; and
&ldquo;float&rdquo; in this case).
</p>
</dd>
<dt><code>-fno-elide-type</code></dt>
<dd><a name="index-fno_002delide_002dtype"></a>
<a name="index-felide_002dtype"></a>
<p>By default when the C++ frontend prints diagnostics showing mismatching
template types, common parts of the types are printed as &ldquo;[...]&rdquo; to
simplify the error message. For example:
</p>
<div class="smallexample">
<pre class="smallexample"> could not convert 'std::map&lt;int, std::vector&lt;double&gt; &gt;()'
from 'map&lt;[...],vector&lt;double&gt;&gt;' to 'map&lt;[...],vector&lt;float&gt;&gt;
</pre></div>
<p>Specifying the <samp>-fno-elide-type</samp> flag suppresses that behavior.
This flag also affects the output of the
<samp>-fdiagnostics-show-template-tree</samp> flag.
</p>
</dd>
<dt><code>-fno-show-column</code></dt>
<dd><a name="index-fno_002dshow_002dcolumn"></a>
<p>Do not print column numbers in diagnostics. This may be necessary if
diagnostics are being scanned by a program that does not understand the
column numbers, such as <code>dejagnu</code>.
</p>
</dd>
</dl>
<hr>
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Next: <a href="Warning-Options.html#Warning-Options" accesskey="n" rel="next">Warning Options</a>, Previous: <a href="Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options.html#Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options" accesskey="p" rel="prev">Objective-C and Objective-C++ Dialect Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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