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(gcc-300.info)Gcov Intro

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Introduction to `gcov'
======================

   `gcov' is a test coverage program.  Use it in concert with GCC to
analyze your programs to help create more efficient, faster running
code.  You can use `gcov' as a profiling tool to help discover where
your optimization efforts will best affect your code.  You can also use
`gcov' along with the other profiling tool, `gprof', to assess which
parts of your code use the greatest amount of computing time.

   Profiling tools help you analyze your code's performance.  Using a
profiler such as `gcov' or `gprof', you can find out some basic
performance statistics, such as:

   * how often each line of code executes

   * what lines of code are actually executed

   * how much computing time each section of code uses

   Once you know these things about how your code works when compiled,
you can look at each module to see which modules should be optimized.
`gcov' helps you determine where to work on optimization.

   Software developers also use coverage testing in concert with
testsuites, to make sure software is actually good enough for a release.
Testsuites can verify that a program works as expected; a coverage
program tests to see how much of the program is exercised by the
testsuite.  Developers can then determine what kinds of test cases need
to be added to the testsuites to create both better testing and a better
final product.

   You should compile your code without optimization if you plan to use
`gcov' because the optimization, by combining some lines of code into
one function, may not give you as much information as you need to look
for `hot spots' where the code is using a great deal of computer time.
Likewise, because `gcov' accumulates statistics by line (at the lowest
resolution), it works best with a programming style that places only
one statement on each line.  If you use complicated macros that expand
to loops or to other control structures, the statistics are less
helpful--they only report on the line where the macro call appears.  If
your complex macros behave like functions, you can replace them with
inline functions to solve this problem.

   `gcov' creates a logfile called `SOURCEFILE.gcov' which indicates
how many times each line of a source file `SOURCEFILE.c' has executed.
You can use these logfiles along with `gprof' to aid in fine-tuning the
performance of your programs.  `gprof' gives timing information you can
use along with the information you get from `gcov'.

   `gcov' works only on code compiled with GCC.  It is not compatible
with any other profiling or test coverage mechanism.