arm-linux-gcov.1

arm-linux.rar

.IX Item "--unconditional-branches"
.PD
When branch counts are given, include those of unconditional branches.
Unconditional branches are normally not interesting.
.PP
\&\fBgcov\fR should be run with the current directory the same as that
when you invoked the compiler. Otherwise it will not be able to locate
the source files. \fBgcov\fR produces files called
\&\fI\fImangledname\fI.gcov\fR in the current directory. These contain
the coverage information of the source file they correspond to.
One \fI.gcov\fR file is produced for each source file containing code,
which was compiled to produce the data files. The \fImangledname\fR part
of the output file name is usually simply the source file name, but can
be something more complicated if the \fB\-l\fR or \fB\-p\fR options are
given. Refer to those options for details.
.PP
The \fI.gcov\fR files contain the ':' separated fields along with
program source code. The format is
.PP
.Vb 1
\&        <execution_count>:<line_number>:<source line text>
.Ve
.PP
Additional block information may succeed each line, when requested by
command line option. The \fIexecution_count\fR is \fB\-\fR for lines
containing no code and \fB#####\fR for lines which were never
executed. Some lines of information at the start have \fIline_number\fR
of zero.
.PP
When printing percentages, 0% and 100% are only printed when the values
are \fIexactly\fR 0% and 100% respectively. Other values which would
conventionally be rounded to 0% or 100% are instead printed as the
nearest non-boundary value.
.PP
When using \fBgcov\fR, you must first compile your program with two
special \s-1GCC\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 object file is located.
.PP
Running the program will cause profile output to be generated.  For each
source file compiled with \fB\-fprofile\-arcs\fR, an accompanying
\&\fI.gcda\fR file will be placed in the object file directory.
.PP
Running \fBgcov\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 \fItmp.c\fR, this
is what you see when you use the basic \fBgcov\fR facility:
.PP
.Vb 5
\&        $ gcc -fprofile-arcs -ftest-coverage tmp.c
\&        $ a.out
\&        $ gcov tmp.c
\&        90.00% of 10 source lines executed in file tmp.c
\&        Creating tmp.c.gcov.
.Ve
.PP
The file \fItmp.c.gcov\fR contains output from \fBgcov\fR.
Here is a sample:
.PP
.Vb 23
\&                -:    0:Source:tmp.c
\&                -:    0:Graph:tmp.gcno
\&                -:    0:Data:tmp.gcda
\&                -:    0:Runs:1
\&                -:    0:Programs:1
\&                -:    1:#include <stdio.h>
\&                -:    2:
\&                -:    3:int main (void)
\&        function main called 1 returned 1 blocks executed 75%
\&                1:    4:{
\&                1:    5:  int i, total;
\&                -:    6:
\&                1:    7:  total = 0;
\&                -:    8:
\&               11:    9:  for (i = 0; i < 10; i++)
\&               10:   10:    total += i;
\&                -:   11:
\&                1:   12:  if (total != 45)
\&            #####:   13:    printf ("Failure\en");
\&                -:   14:  else
\&                1:   15:    printf ("Success\en");
\&                1:   16:  return 0;
\&                -:   17:}
.Ve
.PP
When you use the \fB\-a\fR option, you will get individual block
counts, and the output looks like this:
.PP
.Vb 30
\&                -:    0:Source:tmp.c
\&                -:    0:Graph:tmp.gcno
\&                -:    0:Data:tmp.gcda
\&                -:    0:Runs:1
\&                -:    0:Programs:1
\&                -:    1:#include <stdio.h>
\&                -:    2:
\&                -:    3:int main (void)
\&        function main called 1 returned 1 blocks executed 75%
\&                1:    4:{
\&                1:    4-block  0
\&                1:    5:  int i, total;
\&                -:    6:
\&                1:    7:  total = 0;
\&                -:    8:
\&               11:    9:  for (i = 0; i < 10; i++)
\&               11:    9-block  0
\&               10:   10:    total += i;
\&               10:   10-block  0
\&                -:   11:
\&                1:   12:  if (total != 45)
\&                1:   12-block  0
\&            #####:   13:    printf ("Failure\en");
\&            $$$$$:   13-block  0
\&                -:   14:  else
\&                1:   15:    printf ("Success\en");
\&                1:   15-block  0
\&                1:   16:  return 0;
\&                1:   16-block  0
\&                -:   17:}
.Ve
.PP
In this mode, each basic block is only shown on one line \*(-- the last
line of the block. A multi-line block will only contribute to the
execution count of that last line, and other lines will not be shown
to contain code, unless previous blocks end on those lines.
The total execution count of a line is shown and subsequent lines show
the execution counts for individual blocks that end on that line. After each
block, the branch and call counts of the block will be shown, if the
\&\fB\-b\fR option is given.
.PP
Because of the way \s-1GCC\s0 instruments calls, a call count can be shown
after a line with no individual blocks.
As you can see, line 13 contains a basic block that was not executed.
.PP
When you use the \fB\-b\fR option, your output looks like this:
.PP
.Vb 6
\&        $ gcov -b tmp.c
\&        90.00% of 10 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
.PP
Here is a sample of a resulting \fItmp.c.gcov\fR file:
.PP
.Vb 29
\&                -:    0:Source:tmp.c
\&                -:    0:Graph:tmp.gcno
\&                -:    0:Data:tmp.gcda
\&                -:    0:Runs:1
\&                -:    0:Programs:1
\&                -:    1:#include <stdio.h>
\&                -:    2:
\&                -:    3:int main (void)
\&        function main called 1 returned 1 blocks executed 75%
\&                1:    4:{
\&                1:    5:  int i, total;
\&                -:    6:
\&                1:    7:  total = 0;
\&                -:    8:
\&               11:    9:  for (i = 0; i < 10; i++)
\&        branch  0 taken 91% (fallthrough)
\&        branch  1 taken 9%
\&               10:   10:    total += i;
\&                -:   11:
\&                1:   12:  if (total != 45)
\&        branch  0 taken 0% (fallthrough)
\&        branch  1 taken 100%
\&            #####:   13:    printf ("Failure\en");
\&        call    0 never executed
\&                -:   14:  else
\&                1:   15:    printf ("Success\en");
\&        call    0 called 1 returned 100%
\&                1:   16:  return 0;
\&                -:   17:}
.Ve
.PP
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 \fI.gcda\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 run(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 \fI.gcda\fR files is saved immediately before the program
exits.  For each source file compiled with \fB\-fprofile\-arcs\fR, the
profiling code first attempts to read in an existing \fI.gcda\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.
.Sh "Using \fBgcov\fP with \s-1GCC\s0 Optimization"
.IX Subsection "Using gcov with GCC Optimization"
If you plan to use \fBgcov\fR to help optimize your code, you must
first compile your program with two special \s-1GCC\s0 options:
\&\fB\-fprofile\-arcs \-ftest\-coverage\fR.  Aside from that, you can use any
other \s-1GCC\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
.PP
can be compiled into one instruction on some machines.  In this case,
there is no way for \fBgcov\fR to calculate separate execution counts
for each line because there isn't separate code for each line.  Hence
the \fBgcov\fR output looks like this if you compiled the program with
optimization:
.PP
.Vb 4
\&              100:   12:if (a != b)
\&              100:   13:  c = 1;
\&              100:   14:else
\&              100:   15:  c = 0;
.Ve
.PP
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.
.PP
Inlineable functions can create unexpected line counts.  Line counts are
shown for the source code of the inlineable function, but what is shown
depends on where the function is inlined, or if it is not inlined at all.
.PP
If the function is not inlined, the compiler must emit an out of line
copy of the function, in any object file that needs it.  If
\&\fIfileA.o\fR and \fIfileB.o\fR both contain out of line bodies of a
particular inlineable function, they will also both contain coverage
counts for that function.  When \fIfileA.o\fR and \fIfileB.o\fR are
linked together, the linker will, on many systems, select one of those
out of line bodies for all calls to that function, and remove or ignore
the other.  Unfortunately, it will not remove the coverage counters for
the unused function body.  Hence when instrumented, all but one use of
that function will show zero counts.
.PP
If the function is inlined in several places, the block structure in
each location might not be the same.  For instance, a condition might
now be calculable at compile time in some instances.  Because the
coverage of all the uses of the inline function will be shown for the
same source lines, the line counts themselves might seem inconsistent.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), \fIgcc\fR\|(1) and the Info entry for \fIgcc\fR.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003
Free Software Foundation, Inc.
.PP
Permission is granted to copy, distribute and/or modify this document
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``\s-1GNU\s0 General Public License'' and ``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 \fIgfdl\fR\|(7) man page.
.PP
(a) The \s-1FSF\s0's Front-Cover Text is:
.PP
.Vb 1
\&     A GNU Manual
.Ve
.PP
(b) The \s-1FSF\s0's Back-Cover Text is:
.PP
.Vb 3
\&     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.
.Ve