Invoking-Gcov.html 21 KB

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  62. <a name="Invoking-Gcov"></a>
  63. <div class="header">
  64. <p>
  65. Next: <a href="Gcov-and-Optimization.html#Gcov-and-Optimization" accesskey="n" rel="next">Gcov and Optimization</a>, Previous: <a href="Gcov-Intro.html#Gcov-Intro" accesskey="p" rel="prev">Gcov Intro</a>, Up: <a href="Gcov.html#Gcov" accesskey="u" rel="up">Gcov</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>
  66. </div>
  67. <hr>
  68. <a name="Invoking-gcov"></a>
  69. <h3 class="section">10.2 Invoking <code>gcov</code></h3>
  70. <div class="smallexample">
  71. <pre class="smallexample">gcov <span class="roman">[</span><var>options</var><span class="roman">]</span> <var>files</var>
  72. </pre></div>
  73. <p><code>gcov</code> accepts the following options:
  74. </p>
  75. <dl compact="compact">
  76. <dt><code>-a</code></dt>
  77. <dt><code>--all-blocks</code></dt>
  78. <dd><p>Write individual execution counts for every basic block. Normally gcov
  79. outputs execution counts only for the main blocks of a line. With this
  80. option you can determine if blocks within a single line are not being
  81. executed.
  82. </p>
  83. </dd>
  84. <dt><code>-b</code></dt>
  85. <dt><code>--branch-probabilities</code></dt>
  86. <dd><p>Write branch frequencies to the output file, and write branch summary
  87. info to the standard output. This option allows you to see how often
  88. each branch in your program was taken. Unconditional branches will not
  89. be shown, unless the <samp>-u</samp> option is given.
  90. </p>
  91. </dd>
  92. <dt><code>-c</code></dt>
  93. <dt><code>--branch-counts</code></dt>
  94. <dd><p>Write branch frequencies as the number of branches taken, rather than
  95. the percentage of branches taken.
  96. </p>
  97. </dd>
  98. <dt><code>-d</code></dt>
  99. <dt><code>--display-progress</code></dt>
  100. <dd><p>Display the progress on the standard output.
  101. </p>
  102. </dd>
  103. <dt><code>-f</code></dt>
  104. <dt><code>--function-summaries</code></dt>
  105. <dd><p>Output summaries for each function in addition to the file level summary.
  106. </p>
  107. </dd>
  108. <dt><code>-h</code></dt>
  109. <dt><code>--help</code></dt>
  110. <dd><p>Display help about using <code>gcov</code> (on the standard output), and
  111. exit without doing any further processing.
  112. </p>
  113. </dd>
  114. <dt><code>-i</code></dt>
  115. <dt><code>--intermediate-format</code></dt>
  116. <dd><p>Output gcov file in an easy-to-parse intermediate text format that can
  117. be used by <code>lcov</code> or other tools. The output is a single
  118. <samp>.gcov</samp> file per <samp>.gcda</samp> file. No source code is required.
  119. </p>
  120. <p>The format of the intermediate <samp>.gcov</samp> file is plain text with
  121. one entry per line
  122. </p>
  123. <div class="smallexample">
  124. <pre class="smallexample">file:<var>source_file_name</var>
  125. function:<var>line_number</var>,<var>execution_count</var>,<var>function_name</var>
  126. lcount:<var>line number</var>,<var>execution_count</var>
  127. branch:<var>line_number</var>,<var>branch_coverage_type</var>
  128. Where the <var>branch_coverage_type</var> is
  129. notexec (Branch not executed)
  130. taken (Branch executed and taken)
  131. nottaken (Branch executed, but not taken)
  132. There can be multiple <var>file</var> entries in an intermediate gcov
  133. file. All entries following a <var>file</var> pertain to that source file
  134. until the next <var>file</var> entry.
  135. </pre></div>
  136. <p>Here is a sample when <samp>-i</samp> is used in conjunction with <samp>-b</samp> option:
  137. </p>
  138. <div class="smallexample">
  139. <pre class="smallexample">file:array.cc
  140. function:11,1,_Z3sumRKSt6vectorIPiSaIS0_EE
  141. function:22,1,main
  142. lcount:11,1
  143. lcount:12,1
  144. lcount:14,1
  145. branch:14,taken
  146. lcount:26,1
  147. branch:28,nottaken
  148. </pre></div>
  149. </dd>
  150. <dt><code>-l</code></dt>
  151. <dt><code>--long-file-names</code></dt>
  152. <dd><p>Create long file names for included source files. For example, if the
  153. header file <samp>x.h</samp> contains code, and was included in the file
  154. <samp>a.c</samp>, then running <code>gcov</code> on the file <samp>a.c</samp> will
  155. produce an output file called <samp>a.c##x.h.gcov</samp> instead of
  156. <samp>x.h.gcov</samp>. This can be useful if <samp>x.h</samp> is included in
  157. multiple source files and you want to see the individual
  158. contributions. If you use the &lsquo;<samp>-p</samp>&rsquo; option, both the including
  159. and included file names will be complete path names.
  160. </p>
  161. </dd>
  162. <dt><code>-m</code></dt>
  163. <dt><code>--demangled-names</code></dt>
  164. <dd><p>Display demangled function names in output. The default is to show
  165. mangled function names.
  166. </p>
  167. </dd>
  168. <dt><code>-n</code></dt>
  169. <dt><code>--no-output</code></dt>
  170. <dd><p>Do not create the <code>gcov</code> output file.
  171. </p>
  172. </dd>
  173. <dt><code>-o <var>directory|file</var></code></dt>
  174. <dt><code>--object-directory <var>directory</var></code></dt>
  175. <dt><code>--object-file <var>file</var></code></dt>
  176. <dd><p>Specify either the directory containing the gcov data files, or the
  177. object path name. The <samp>.gcno</samp>, and
  178. <samp>.gcda</samp> data files are searched for using this option. If a directory
  179. is specified, the data files are in that directory and named after the
  180. input file name, without its extension. If a file is specified here,
  181. the data files are named after that file, without its extension.
  182. </p>
  183. </dd>
  184. <dt><code>-p</code></dt>
  185. <dt><code>--preserve-paths</code></dt>
  186. <dd><p>Preserve complete path information in the names of generated
  187. <samp>.gcov</samp> files. Without this option, just the filename component is
  188. used. With this option, all directories are used, with &lsquo;<samp>/</samp>&rsquo; characters
  189. translated to &lsquo;<samp>#</samp>&rsquo; characters, <samp>.</samp> directory components
  190. removed and unremoveable <samp>..</samp>
  191. components renamed to &lsquo;<samp>^</samp>&rsquo;. This is useful if sourcefiles are in several
  192. different directories.
  193. </p>
  194. </dd>
  195. <dt><code>-r</code></dt>
  196. <dt><code>--relative-only</code></dt>
  197. <dd><p>Only output information about source files with a relative pathname
  198. (after source prefix elision). Absolute paths are usually system
  199. header files and coverage of any inline functions therein is normally
  200. uninteresting.
  201. </p>
  202. </dd>
  203. <dt><code>-s <var>directory</var></code></dt>
  204. <dt><code>--source-prefix <var>directory</var></code></dt>
  205. <dd><p>A prefix for source file names to remove when generating the output
  206. coverage files. This option is useful when building in a separate
  207. directory, and the pathname to the source directory is not wanted when
  208. determining the output file names. Note that this prefix detection is
  209. applied before determining whether the source file is absolute.
  210. </p>
  211. </dd>
  212. <dt><code>-u</code></dt>
  213. <dt><code>--unconditional-branches</code></dt>
  214. <dd><p>When branch probabilities are given, include those of unconditional branches.
  215. Unconditional branches are normally not interesting.
  216. </p>
  217. </dd>
  218. <dt><code>-v</code></dt>
  219. <dt><code>--version</code></dt>
  220. <dd><p>Display the <code>gcov</code> version number (on the standard output),
  221. and exit without doing any further processing.
  222. </p>
  223. </dd>
  224. <dt><code>-w</code></dt>
  225. <dt><code>--verbose</code></dt>
  226. <dd><p>Print verbose informations related to basic blocks and arcs.
  227. </p>
  228. </dd>
  229. <dt><code>-x</code></dt>
  230. <dt><code>--hash-filenames</code></dt>
  231. <dd><p>By default, gcov uses the full pathname of the source files to to create
  232. an output filename. This can lead to long filenames that can overflow
  233. filesystem limits. This option creates names of the form
  234. <samp><var>source-file</var>##<var>md5</var>.gcov</samp>,
  235. where the <var>source-file</var> component is the final filename part and
  236. the <var>md5</var> component is calculated from the full mangled name that
  237. would have been used otherwise.
  238. </p>
  239. </dd>
  240. </dl>
  241. <p><code>gcov</code> should be run with the current directory the same as that
  242. when you invoked the compiler. Otherwise it will not be able to locate
  243. the source files. <code>gcov</code> produces files called
  244. <samp><var>mangledname</var>.gcov</samp> in the current directory. These contain
  245. the coverage information of the source file they correspond to.
  246. One <samp>.gcov</samp> file is produced for each source (or header) file
  247. containing code,
  248. which was compiled to produce the data files. The <var>mangledname</var> part
  249. of the output file name is usually simply the source file name, but can
  250. be something more complicated if the &lsquo;<samp>-l</samp>&rsquo; or &lsquo;<samp>-p</samp>&rsquo; options are
  251. given. Refer to those options for details.
  252. </p>
  253. <p>If you invoke <code>gcov</code> with multiple input files, the
  254. contributions from each input file are summed. Typically you would
  255. invoke it with the same list of files as the final link of your executable.
  256. </p>
  257. <p>The <samp>.gcov</samp> files contain the &lsquo;<samp>:</samp>&rsquo; separated fields along with
  258. program source code. The format is
  259. </p>
  260. <div class="smallexample">
  261. <pre class="smallexample"><var>execution_count</var>:<var>line_number</var>:<var>source line text</var>
  262. </pre></div>
  263. <p>Additional block information may succeed each line, when requested by
  264. command line option. The <var>execution_count</var> is &lsquo;<samp>-</samp>&rsquo; for lines
  265. containing no code. Unexecuted lines are marked &lsquo;<samp>#####</samp>&rsquo; or
  266. &lsquo;<samp>=====</samp>&rsquo;, depending on whether they are reachable by
  267. non-exceptional paths or only exceptional paths such as C++ exception
  268. handlers, respectively. Given &lsquo;<samp>-a</samp>&rsquo; option, unexecuted blocks are
  269. marked &lsquo;<samp>$$$$$</samp>&rsquo; or &lsquo;<samp>%%%%%</samp>&rsquo;, depending on whether a basic block
  270. is reachable via non-exceptional or exceptional paths.
  271. </p>
  272. <p>Note that GCC can completely remove the bodies of functions that are
  273. not needed &ndash; for instance if they are inlined everywhere. Such functions
  274. are marked with &lsquo;<samp>-</samp>&rsquo;, which can be confusing.
  275. Use the <samp>-fkeep-inline-functions</samp> and <samp>-fkeep-static-functions</samp>
  276. options to retain these functions and
  277. allow gcov to properly show their <var>execution_count</var>.
  278. </p>
  279. <p>Some lines of information at the start have <var>line_number</var> of zero.
  280. These preamble lines are of the form
  281. </p>
  282. <div class="smallexample">
  283. <pre class="smallexample">-:0:<var>tag</var>:<var>value</var>
  284. </pre></div>
  285. <p>The ordering and number of these preamble lines will be augmented as
  286. <code>gcov</code> development progresses &mdash; do not rely on them remaining
  287. unchanged. Use <var>tag</var> to locate a particular preamble line.
  288. </p>
  289. <p>The additional block information is of the form
  290. </p>
  291. <div class="smallexample">
  292. <pre class="smallexample"><var>tag</var> <var>information</var>
  293. </pre></div>
  294. <p>The <var>information</var> is human readable, but designed to be simple
  295. enough for machine parsing too.
  296. </p>
  297. <p>When printing percentages, 0% and 100% are only printed when the values
  298. are <em>exactly</em> 0% and 100% respectively. Other values which would
  299. conventionally be rounded to 0% or 100% are instead printed as the
  300. nearest non-boundary value.
  301. </p>
  302. <p>When using <code>gcov</code>, you must first compile your program with two
  303. special GCC options: &lsquo;<samp>-fprofile-arcs -ftest-coverage</samp>&rsquo;.
  304. This tells the compiler to generate additional information needed by
  305. gcov (basically a flow graph of the program) and also includes
  306. additional code in the object files for generating the extra profiling
  307. information needed by gcov. These additional files are placed in the
  308. directory where the object file is located.
  309. </p>
  310. <p>Running the program will cause profile output to be generated. For each
  311. source file compiled with <samp>-fprofile-arcs</samp>, an accompanying
  312. <samp>.gcda</samp> file will be placed in the object file directory.
  313. </p>
  314. <p>Running <code>gcov</code> with your program&rsquo;s source file names as arguments
  315. will now produce a listing of the code along with frequency of execution
  316. for each line. For example, if your program is called <samp>tmp.c</samp>, this
  317. is what you see when you use the basic <code>gcov</code> facility:
  318. </p>
  319. <div class="smallexample">
  320. <pre class="smallexample">$ gcc -fprofile-arcs -ftest-coverage tmp.c
  321. $ a.out
  322. $ gcov tmp.c
  323. File 'tmp.c'
  324. Lines executed:90.00% of 10
  325. Creating 'tmp.c.gcov'
  326. </pre></div>
  327. <p>The file <samp>tmp.c.gcov</samp> contains output from <code>gcov</code>.
  328. Here is a sample:
  329. </p>
  330. <div class="smallexample">
  331. <pre class="smallexample"> -: 0:Source:tmp.c
  332. -: 0:Graph:tmp.gcno
  333. -: 0:Data:tmp.gcda
  334. -: 0:Runs:1
  335. -: 0:Programs:1
  336. -: 1:#include &lt;stdio.h&gt;
  337. -: 2:
  338. -: 3:int main (void)
  339. 1: 4:{
  340. 1: 5: int i, total;
  341. -: 6:
  342. 1: 7: total = 0;
  343. -: 8:
  344. 11: 9: for (i = 0; i &lt; 10; i++)
  345. 10: 10: total += i;
  346. -: 11:
  347. 1: 12: if (total != 45)
  348. #####: 13: printf (&quot;Failure\n&quot;);
  349. -: 14: else
  350. 1: 15: printf (&quot;Success\n&quot;);
  351. 1: 16: return 0;
  352. -: 17:}
  353. </pre></div>
  354. <p>When you use the <samp>-a</samp> option, you will get individual block
  355. counts, and the output looks like this:
  356. </p>
  357. <div class="smallexample">
  358. <pre class="smallexample"> -: 0:Source:tmp.c
  359. -: 0:Graph:tmp.gcno
  360. -: 0:Data:tmp.gcda
  361. -: 0:Runs:1
  362. -: 0:Programs:1
  363. -: 1:#include &lt;stdio.h&gt;
  364. -: 2:
  365. -: 3:int main (void)
  366. 1: 4:{
  367. 1: 4-block 0
  368. 1: 5: int i, total;
  369. -: 6:
  370. 1: 7: total = 0;
  371. -: 8:
  372. 11: 9: for (i = 0; i &lt; 10; i++)
  373. 11: 9-block 0
  374. 10: 10: total += i;
  375. 10: 10-block 0
  376. -: 11:
  377. 1: 12: if (total != 45)
  378. 1: 12-block 0
  379. #####: 13: printf (&quot;Failure\n&quot;);
  380. $$$$$: 13-block 0
  381. -: 14: else
  382. 1: 15: printf (&quot;Success\n&quot;);
  383. 1: 15-block 0
  384. 1: 16: return 0;
  385. 1: 16-block 0
  386. -: 17:}
  387. </pre></div>
  388. <p>In this mode, each basic block is only shown on one line &ndash; the last
  389. line of the block. A multi-line block will only contribute to the
  390. execution count of that last line, and other lines will not be shown
  391. to contain code, unless previous blocks end on those lines.
  392. The total execution count of a line is shown and subsequent lines show
  393. the execution counts for individual blocks that end on that line. After each
  394. block, the branch and call counts of the block will be shown, if the
  395. <samp>-b</samp> option is given.
  396. </p>
  397. <p>Because of the way GCC instruments calls, a call count can be shown
  398. after a line with no individual blocks.
  399. As you can see, line 13 contains a basic block that was not executed.
  400. </p>
  401. <p>When you use the <samp>-b</samp> option, your output looks like this:
  402. </p>
  403. <div class="smallexample">
  404. <pre class="smallexample">$ gcov -b tmp.c
  405. File 'tmp.c'
  406. Lines executed:90.00% of 10
  407. Branches executed:80.00% of 5
  408. Taken at least once:80.00% of 5
  409. Calls executed:50.00% of 2
  410. Creating 'tmp.c.gcov'
  411. </pre></div>
  412. <p>Here is a sample of a resulting <samp>tmp.c.gcov</samp> file:
  413. </p>
  414. <div class="smallexample">
  415. <pre class="smallexample"> -: 0:Source:tmp.c
  416. -: 0:Graph:tmp.gcno
  417. -: 0:Data:tmp.gcda
  418. -: 0:Runs:1
  419. -: 0:Programs:1
  420. -: 1:#include &lt;stdio.h&gt;
  421. -: 2:
  422. -: 3:int main (void)
  423. function main called 1 returned 1 blocks executed 75%
  424. 1: 4:{
  425. 1: 5: int i, total;
  426. -: 6:
  427. 1: 7: total = 0;
  428. -: 8:
  429. 11: 9: for (i = 0; i &lt; 10; i++)
  430. branch 0 taken 91% (fallthrough)
  431. branch 1 taken 9%
  432. 10: 10: total += i;
  433. -: 11:
  434. 1: 12: if (total != 45)
  435. branch 0 taken 0% (fallthrough)
  436. branch 1 taken 100%
  437. #####: 13: printf (&quot;Failure\n&quot;);
  438. call 0 never executed
  439. -: 14: else
  440. 1: 15: printf (&quot;Success\n&quot;);
  441. call 0 called 1 returned 100%
  442. 1: 16: return 0;
  443. -: 17:}
  444. </pre></div>
  445. <p>For each function, a line is printed showing how many times the function
  446. is called, how many times it returns and what percentage of the
  447. function&rsquo;s blocks were executed.
  448. </p>
  449. <p>For each basic block, a line is printed after the last line of the basic
  450. block describing the branch or call that ends the basic block. There can
  451. be multiple branches and calls listed for a single source line if there
  452. are multiple basic blocks that end on that line. In this case, the
  453. branches and calls are each given a number. There is no simple way to map
  454. these branches and calls back to source constructs. In general, though,
  455. the lowest numbered branch or call will correspond to the leftmost construct
  456. on the source line.
  457. </p>
  458. <p>For a branch, if it was executed at least once, then a percentage
  459. indicating the number of times the branch was taken divided by the
  460. number of times the branch was executed will be printed. Otherwise, the
  461. message &ldquo;never executed&rdquo; is printed.
  462. </p>
  463. <p>For a call, if it was executed at least once, then a percentage
  464. indicating the number of times the call returned divided by the number
  465. of times the call was executed will be printed. This will usually be
  466. 100%, but may be less for functions that call <code>exit</code> or <code>longjmp</code>,
  467. and thus may not return every time they are called.
  468. </p>
  469. <p>The execution counts are cumulative. If the example program were
  470. executed again without removing the <samp>.gcda</samp> file, the count for the
  471. number of times each line in the source was executed would be added to
  472. the results of the previous run(s). This is potentially useful in
  473. several ways. For example, it could be used to accumulate data over a
  474. number of program runs as part of a test verification suite, or to
  475. provide more accurate long-term information over a large number of
  476. program runs.
  477. </p>
  478. <p>The data in the <samp>.gcda</samp> files is saved immediately before the program
  479. exits. For each source file compiled with <samp>-fprofile-arcs</samp>, the
  480. profiling code first attempts to read in an existing <samp>.gcda</samp> file; if
  481. the file doesn&rsquo;t match the executable (differing number of basic block
  482. counts) it will ignore the contents of the file. It then adds in the
  483. new execution counts and finally writes the data to the file.
  484. </p>
  485. <hr>
  486. <div class="header">
  487. <p>
  488. Next: <a href="Gcov-and-Optimization.html#Gcov-and-Optimization" accesskey="n" rel="next">Gcov and Optimization</a>, Previous: <a href="Gcov-Intro.html#Gcov-Intro" accesskey="p" rel="prev">Gcov Intro</a>, Up: <a href="Gcov.html#Gcov" accesskey="u" rel="up">Gcov</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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