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+.\" ======================================================================
+.\"
+.IX Title "GCOV 1"
+.TH GCOV 1 "gcc-2.97" "2000-11-21" "GNU"
+.UC
+.SH "NAME"
+gcov \- coverage testing tool
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+gcov [\fB\-b\fR] [\fB\-c\fR] [\fB\-v\fR] [\fB\-n\fR] [\fB\-l\fR] [\fB\-f\fR] [\fB\-o\fR \fIdirectory\fR] \fIsourcefile\fR
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+\&\f(CW\*(C`gcov\*(C'\fR is a test coverage program. Use it in concert with \s-1GNU\s0
+\&\s-1CC\s0 to analyze your programs to help create more efficient, faster
+running code. You can use \f(CW\*(C`gcov\*(C'\fR as a profiling tool to help
+discover where your optimization efforts will best affect your code. You
+can also use \f(CW\*(C`gcov\*(C'\fR along with the other profiling tool,
+\&\f(CW\*(C`gprof\*(C'\fR, to assess which parts of your code use the greatest amount
+of computing time.
+.PP
+Profiling tools help you analyze your code's performance. Using a
+profiler such as \f(CW\*(C`gcov\*(C'\fR or \f(CW\*(C`gprof\*(C'\fR, you can find out some
+basic performance statistics, such as:
+.Ip "\(bu" 4
+how often each line of code executes
+.Ip "\(bu" 4
+what lines of code are actually executed
+.Ip "\(bu" 4
+how much computing time each section of code uses
+.PP
+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.
+\&\f(CW\*(C`gcov\*(C'\fR helps you determine where to work on optimization.
+.PP
+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.
+.PP
+You should compile your code without optimization if you plan to use
+\&\f(CW\*(C`gcov\*(C'\fR 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 \f(CW\*(C`gcov\*(C'\fR 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.
+.PP
+\&\f(CW\*(C`gcov\*(C'\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which
+indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR
+has executed. You can use these logfiles along with \f(CW\*(C`gprof\*(C'\fR to aid
+in fine-tuning the performance of your programs. \f(CW\*(C`gprof\*(C'\fR gives
+timing information you can use along with the information you get from
+\&\f(CW\*(C`gcov\*(C'\fR.
+.PP
+\&\f(CW\*(C`gcov\*(C'\fR works only on code compiled with \s-1GNU\s0 \s-1CC\s0. It is not
+compatible with any other profiling or test coverage mechanism.
+.SH "OPTIONS"
+.IX Header "OPTIONS"
+.if n .Ip "\f(CW""\-b""\fR" 4
+.el .Ip "\f(CW\-b\fR" 4
+.IX Item "-b"
+Write branch frequencies to the output file, and write branch summary
+info to the standard output. This option allows you to see how often
+each branch in your program was taken.
+.if n .Ip "\f(CW""\-c""\fR" 4
+.el .Ip "\f(CW\-c\fR" 4
+.IX Item "-c"
+Write branch frequencies as the number of branches taken, rather than
+the percentage of branches taken.
+.if n .Ip "\f(CW""\-v""\fR" 4
+.el .Ip "\f(CW\-v\fR" 4
+.IX Item "-v"
+Display the \f(CW\*(C`gcov\*(C'\fR version number (on the standard error stream).
+.if n .Ip "\f(CW""\-n""\fR" 4
+.el .Ip "\f(CW\-n\fR" 4
+.IX Item "-n"
+Do not create the \f(CW\*(C`gcov\*(C'\fR output file.
+.if n .Ip "\f(CW""\-l""\fR" 4
+.el .Ip "\f(CW\-l\fR" 4
+.IX Item "-l"
+Create long file names for included source files. For example, if the
+header file \fBx.h\fR contains code, and was included in the file
+\&\fBa.c\fR, then running \f(CW\*(C`gcov\*(C'\fR on the file \fBa.c\fR will produce
+an output file called \fBa.c.x.h.gcov\fR instead of \fBx.h.gcov\fR.
+This can be useful if \fBx.h\fR is included in multiple source files.
+.if n .Ip "\f(CW""\-f""\fR" 4
+.el .Ip "\f(CW\-f\fR" 4
+.IX Item "-f"
+Output summaries for each function in addition to the file level summary.
+.if n .Ip "\f(CW""\-o""\fR" 4
+.el .Ip "\f(CW\-o\fR" 4
+.IX Item "-o"
+The directory where the object files live. Gcov will search for \f(CW\*(C`.bb\*(C'\fR,
+\&\f(CW\*(C`.bbg\*(C'\fR, and \f(CW\*(C`.da\*(C'\fR files in this directory.
+.PP
+When using \f(CW\*(C`gcov\*(C'\fR, you must first compile your program with two
+special \s-1GNU\s0 \s-1CC\s0 options: \fB\-fprofile-arcs \-ftest-coverage\fR.
+This tells the compiler to generate additional information needed by
+gcov (basically a flow graph of the program) and also includes
+additional code in the object files for generating the extra profiling
+information needed by gcov. These additional files are placed in the
+directory where the source code is located.
+.PP
+Running the program will cause profile output to be generated. For each
+source file compiled with \-fprofile-arcs, an accompanying \f(CW\*(C`.da\*(C'\fR
+file will be placed in the source directory.
+.PP
+Running \f(CW\*(C`gcov\*(C'\fR with your program's source file names as arguments
+will now produce a listing of the code along with frequency of execution
+for each line. For example, if your program is called \fBtmp.c\fR, this
+is what you see when you use the basic \f(CW\*(C`gcov\*(C'\fR facility:
+.PP
+.Vb 5
+\& $ gcc -fprofile-arcs -ftest-coverage tmp.c
+\& $ a.out
+\& $ gcov tmp.c
+\& 87.50% of 8 source lines executed in file tmp.c
+\& Creating tmp.c.gcov.
+.Ve
+The file \fItmp.c.gcov\fR contains output from \f(CW\*(C`gcov\*(C'\fR.
+Here is a sample:
+.PP
+.Vb 3
+\& main()
+\& {
+\& 1 int i, total;
+.Ve
+.Vb 1
+\& 1 total = 0;
+.Ve
+.Vb 2
+\& 11 for (i = 0; i < 10; i++)
+\& 10 total += i;
+.Ve
+.Vb 5
+\& 1 if (total != 45)
+\& ###### printf ("Failure\en");
+\& else
+\& 1 printf ("Success\en");
+\& 1 }
+.Ve
+When you use the \fB\-b\fR option, your output looks like this:
+.PP
+.Vb 6
+\& $ gcov -b tmp.c
+\& 87.50% of 8 source lines executed in file tmp.c
+\& 80.00% of 5 branches executed in file tmp.c
+\& 80.00% of 5 branches taken at least once in file tmp.c
+\& 50.00% of 2 calls executed in file tmp.c
+\& Creating tmp.c.gcov.
+.Ve
+Here is a sample of a resulting \fItmp.c.gcov\fR file:
+.PP
+.Vb 3
+\& main()
+\& {
+\& 1 int i, total;
+.Ve
+.Vb 1
+\& 1 total = 0;
+.Ve
+.Vb 5
+\& 11 for (i = 0; i < 10; i++)
+\& branch 0 taken = 91%
+\& branch 1 taken = 100%
+\& branch 2 taken = 100%
+\& 10 total += i;
+.Ve
+.Vb 9
+\& 1 if (total != 45)
+\& branch 0 taken = 100%
+\& ###### printf ("Failure\en");
+\& call 0 never executed
+\& branch 1 never executed
+\& else
+\& 1 printf ("Success\en");
+\& call 0 returns = 100%
+\& 1 }
+.Ve
+For each basic block, a line is printed after the last line of the basic
+block describing the branch or call that ends the basic block. There can
+be multiple branches and calls listed for a single source line if there
+are multiple basic blocks that end on that line. In this case, the
+branches and calls are each given a number. There is no simple way to map
+these branches and calls back to source constructs. In general, though,
+the lowest numbered branch or call will correspond to the leftmost construct
+on the source line.
+.PP
+For a branch, if it was executed at least once, then a percentage
+indicating the number of times the branch was taken divided by the
+number of times the branch was executed will be printed. Otherwise, the
+message ``never executed'' is printed.
+.PP
+For a call, if it was executed at least once, then a percentage
+indicating the number of times the call returned divided by the number
+of times the call was executed will be printed. This will usually be
+100%, but may be less for functions call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,
+and thus may not return every time they are called.
+.PP
+The execution counts are cumulative. If the example program were
+executed again without removing the \f(CW\*(C`.da\*(C'\fR file, the count for the
+number of times each line in the source was executed would be added to
+the results of the previous \fIrun\fR\|(s). This is potentially useful in
+several ways. For example, it could be used to accumulate data over a
+number of program runs as part of a test verification suite, or to
+provide more accurate long-term information over a large number of
+program runs.
+.PP
+The data in the \f(CW\*(C`.da\*(C'\fR files is saved immediately before the program
+exits. For each source file compiled with \-fprofile-arcs, the profiling
+code first attempts to read in an existing \f(CW\*(C`.da\*(C'\fR file; if the file
+doesn't match the executable (differing number of basic block counts) it
+will ignore the contents of the file. It then adds in the new execution
+counts and finally writes the data to the file.
+.if n .Sh "Using \f(CW""gcov""\fP with \s-1GCC\s0 Optimization"
+.el .Sh "Using \f(CWgcov\fP with \s-1GCC\s0 Optimization"
+.IX Subsection "Using gcov with GCC Optimization"
+If you plan to use \f(CW\*(C`gcov\*(C'\fR to help optimize your code, you must
+first compile your program with two special \s-1GNU\s0 \s-1CC\s0 options:
+\&\fB\-fprofile-arcs \-ftest-coverage\fR. Aside from that, you can use any
+other \s-1GNU\s0 \s-1CC\s0 options; but if you want to prove that every single line
+in your program was executed, you should not compile with optimization
+at the same time. On some machines the optimizer can eliminate some
+simple code lines by combining them with other lines. For example, code
+like this:
+.PP
+.Vb 4
+\& if (a != b)
+\& c = 1;
+\& else
+\& c = 0;
+.Ve
+can be compiled into one instruction on some machines. In this case,
+there is no way for \f(CW\*(C`gcov\*(C'\fR to calculate separate execution counts
+for each line because there isn't separate code for each line. Hence
+the \f(CW\*(C`gcov\*(C'\fR output looks like this if you compiled the program with
+optimization:
+.PP
+.Vb 4
+\& 100 if (a != b)
+\& 100 c = 1;
+\& 100 else
+\& 100 c = 0;
+.Ve
+The output shows that this block of code, combined by optimization,
+executed 100 times. In one sense this result is correct, because there
+was only one instruction representing all four of these lines. However,
+the output does not indicate how many times the result was 0 and how
+many times the result was 1.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+\&\fIgcc\fR\|(1) and the Info entry for \fIgcc\fR.
+.SH "COPYRIGHT"
+.IX Header "COPYRIGHT"
+Copyright 1996, 1997, 1999, 2000 Free Software Foundation, Inc.
+.PP
+Permission is granted to make and distribute verbatim copies of this
+manual provided the copyright notice and this permission notice are
+preserved on all copies.
+.PP
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided also that the
+entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.
+.PP
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be included in translations
+approved by the Free Software Foundation instead of in the original
+English.
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