@c Copyright (C) 1996, 1997, 1999, 2000, 2001,
-@c 2002 Free Software Foundation, Inc.
+@c 2002, 2003, 2004, 2005, 2008 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@ignore
@c man begin COPYRIGHT
-Copyright @copyright{} 1996, 1997, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+Copyright @copyright{} 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+2008 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1 or
+under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``GNU General Public License'' and ``Funding
Free Software'', the Front-Cover texts being (a) (see below), and with
@end ignore
@node Gcov
-@chapter @command{gcov}: a Test Coverage Program
+@chapter @command{gcov}---a Test Coverage Program
@command{gcov} is a tool you can use in conjunction with GCC to
test code coverage in your programs.
@menu
-* Gcov Intro:: Introduction to gcov.
-* Invoking Gcov:: How to use gcov.
+* Gcov Intro:: Introduction to gcov.
+* Invoking Gcov:: How to use gcov.
* Gcov and Optimization:: Using gcov with GCC optimization.
* Gcov Data Files:: The files used by gcov.
+* Cross-profiling:: Data file relocation.
@end menu
@node Gcov Intro
@c man end
@node Invoking Gcov
-@section Invoking gcov
+@section Invoking @command{gcov}
@smallexample
-gcov @r{[}@var{options}@r{]} @var{sourcefile}
+gcov @r{[}@var{options}@r{]} @var{sourcefiles}
@end smallexample
@command{gcov} accepts the following options:
@ignore
@c man begin SYNOPSIS
gcov [@option{-v}|@option{--version}] [@option{-h}|@option{--help}]
+ [@option{-a}|@option{--all-blocks}]
[@option{-b}|@option{--branch-probabilities}]
[@option{-c}|@option{--branch-counts}]
[@option{-n}|@option{--no-output}]
[@option{-l}|@option{--long-file-names}]
[@option{-p}|@option{--preserve-paths}]
[@option{-f}|@option{--function-summaries}]
- [@option{-o}|@option{--object-directory} @var{directory|file}] @var{sourcefile}
+ [@option{-o}|@option{--object-directory} @var{directory|file}] @var{sourcefiles}
+ [@option{-u}|@option{--unconditional-branches}]
@c man end
@c man begin SEEALSO
gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entry for @file{gcc}.
Display the @command{gcov} version number (on the standard output),
and exit without doing any further processing.
+@item -a
+@itemx --all-blocks
+Write individual execution counts for every basic block. Normally gcov
+outputs execution counts only for the main blocks of a line. With this
+option you can determine if blocks within a single line are not being
+executed.
+
@item -b
@itemx --branch-probabilities
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.
+each branch in your program was taken. Unconditional branches will not
+be shown, unless the @option{-u} option is given.
@item -c
@itemx --branch-counts
header file @file{x.h} contains code, and was included in the file
@file{a.c}, then running @command{gcov} on the file @file{a.c} will produce
an output file called @file{a.c##x.h.gcov} instead of @file{x.h.gcov}.
-This can be useful if @file{x.h} is included in multiple source files.
+This can be useful if @file{x.h} is included in multiple source
+files. If you use the @samp{-p} option, both the including and
+included file names will be complete path names.
@item -p
@itemx --preserve-paths
Preserve complete path information in the names of generated
-@file{.gcov} files. Without this option, just the filename component is
-used. With this option, all directories are used, with '/' characters
-translated to '#' characters, '.' directory components removed and '..'
-components renamed to '^'. This is useful if sourcefiles are in several
-different directories. It also affects the @samp{-l} option.
+@file{.gcov} files. Without this option, just the filename component is
+used. With this option, all directories are used, with @samp{/} characters
+translated to @samp{#} characters, @file{.} directory components
+removed and @file{..}
+components renamed to @samp{^}. This is useful if sourcefiles are in several
+different directories. It also affects the @samp{-l} option.
@item -f
@itemx --function-summaries
@itemx --object-directory @var{directory}
@itemx --object-file @var{file}
Specify either the directory containing the gcov data files, or the
-object path name. The @file{.bb}, @file{.bbg}, and
-@file{.da} data files are searched for using this option. If a directory
+object path name. The @file{.gcno}, and
+@file{.gcda} data files are searched for using this option. If a directory
is specified, the data files are in that directory and named after the
-source file name, without its extension. If a file is specified here,
-the data files are named after that file, without its extension. If this
+source file name, without its extension. If a file is specified here,
+the data files are named after that file, without its extension. If this
option is not supplied, it defaults to the current directory.
+@item -u
+@itemx --unconditional-branches
+When branch probabilities are given, include those of unconditional branches.
+Unconditional branches are normally not interesting.
+
@end table
-Gcov 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. Gcov produces files called @file{@var{mangledname}.gcov} in the
-current directory. These contain the coverage information of the source
-file they correspond to. One @file{.gcov} file is produced for each
-source file containing code, which was compiled to produce the data
-files. The @file{.gcov} files contain the ':' separated fields along
-with program source code. The format is
+@command{gcov} 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. @command{gcov} produces files called
+@file{@var{mangledname}.gcov} in the current directory. These contain
+the coverage information of the source file they correspond to.
+One @file{.gcov} file is produced for each source file containing code,
+which was compiled to produce the data files. The @var{mangledname} part
+of the output file name is usually simply the source file name, but can
+be something more complicated if the @samp{-l} or @samp{-p} options are
+given. Refer to those options for details.
+
+The @file{.gcov} files contain the @samp{:} separated fields along with
+program source code. The format is
@smallexample
@var{execution_count}:@var{line_number}:@var{source line text}
@end smallexample
Additional block information may succeed each line, when requested by
-command line option. The @var{execution_count} is @samp{-} for lines
-containing no code and @samp{#####} for lines which were never
-executed. Some lines of information at the start have @var{line_number}
-of zero.
+command line option. The @var{execution_count} is @samp{-} for lines
+containing no code and @samp{#####} for lines which were never executed.
+Some lines of information at the start have @var{line_number} of zero.
+
+The preamble lines are of the form
+
+@smallexample
+-:0:@var{tag}:@var{value}
+@end smallexample
+
+The ordering and number of these preamble lines will be augmented as
+@command{gcov} development progresses --- do not rely on them remaining
+unchanged. Use @var{tag} to locate a particular preamble line.
+
+The additional block information is of the form
+
+@smallexample
+@var{tag} @var{information}
+@end smallexample
+
+The @var{information} is human readable, but designed to be simple
+enough for machine parsing too.
When printing percentages, 0% and 100% are only printed when the values
-are @emph{exactly} 0% and 100% respectively. Other values which would
+are @emph{exactly} 0% and 100% respectively. Other values which would
conventionally be rounded to 0% or 100% are instead printed as the
nearest non-boundary value.
directory where the object file is located.
Running the program will cause profile output to be generated. For each
-source file compiled with @option{-fprofile-arcs}, an accompanying @file{.da}
-file will be placed in the object file directory.
+source file compiled with @option{-fprofile-arcs}, an accompanying
+@file{.gcda} file will be placed in the object file directory.
Running @command{gcov} with your program's source file names as arguments
will now produce a listing of the code along with frequency of execution
@smallexample
-: 0:Source:tmp.c
- -: 0:Object:tmp.bb
+ -: 0:Graph:tmp.gcno
+ -: 0:Data:tmp.gcda
+ -: 0:Runs:1
+ -: 0:Programs:1
-: 1:#include <stdio.h>
-: 2:
-: 3:int main (void)
1: 4:@{
1: 5: int i, total;
- -: 6:
+ -: 6:
1: 7: total = 0;
- -: 8:
+ -: 8:
11: 9: for (i = 0; i < 10; i++)
10: 10: total += i;
- -: 11:
+ -: 11:
1: 12: if (total != 45)
#####: 13: printf ("Failure\n");
-: 14: else
1: 15: printf ("Success\n");
1: 16: return 0;
- 1: 17:@}
+ -: 17:@}
@end smallexample
+When you use the @option{-a} option, you will get individual block
+counts, and the output looks like this:
+
+@smallexample
+ -: 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)
+ 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\n");
+ $$$$$: 13-block 0
+ -: 14: else
+ 1: 15: printf ("Success\n");
+ 1: 15-block 0
+ 1: 16: return 0;
+ 1: 16-block 0
+ -: 17:@}
+@end smallexample
+
+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
+@option{-b} option is given.
+
+Because of the way GCC 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.
+
@need 450
When you use the @option{-b} option, your output looks like this:
@smallexample
-: 0:Source:tmp.c
- -: 0:Object:tmp.bb
+ -: 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:
+ -: 6:
1: 7: total = 0;
- -: 8:
+ -: 8:
11: 9: for (i = 0; i < 10; i++)
-branch 0: taken 90%
-branch 1: taken 100%
-branch 2: taken 100%
+branch 0 taken 91% (fallthrough)
+branch 1 taken 9%
10: 10: total += i;
- -: 11:
+ -: 11:
1: 12: if (total != 45)
-branch 0: taken 100%
+branch 0 taken 0% (fallthrough)
+branch 1 taken 100%
#####: 13: printf ("Failure\n");
-call 0: never executed
-branch 1: never executed
+call 0 never executed
-: 14: else
1: 15: printf ("Success\n");
-call 0: returns 100%
+call 0 called 1 returned 100%
1: 16: return 0;
- 1: 17:@}
+ -: 17:@}
@end smallexample
+For each function, a line is printed showing how many times the function
+is called, how many times it returns and what percentage of the
+function's blocks were executed.
+
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
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 @code{exit} or @code{longjmp},
+100%, but may be less for functions that call @code{exit} or @code{longjmp},
and thus may not return every time they are called.
The execution counts are cumulative. If the example program were
-executed again without removing the @file{.da} file, the count for the
+executed again without removing the @file{.gcda} 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
provide more accurate long-term information over a large number of
program runs.
-The data in the @file{.da} files is saved immediately before the program
+The data in the @file{.gcda} files is saved immediately before the program
exits. For each source file compiled with @option{-fprofile-arcs}, the
-profiling code first attempts to read in an existing @file{.da} file; if
+profiling code first attempts to read in an existing @file{.gcda} 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.
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.
+
+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.
+
+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
+@file{fileA.o} and @file{fileB.o} both contain out of line bodies of a
+particular inlineable function, they will also both contain coverage
+counts for that function. When @file{fileA.o} and @file{fileB.o} 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.
+
+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.
+
@c man end
@node Gcov Data Files
@command{gcov} uses two files for profiling. The names of these files
are derived from the original @emph{object} file by substituting the
-file suffix with either @file{.bbg}, or @file{.da}. All of these files
+file suffix with either @file{.gcno}, or @file{.gcda}. All of these files
are placed in the same directory as the object file, and contain data
stored in a platform-independent format.
-The @file{.bbg} files is generated when the source file is compiled with
+The @file{.gcno} file is generated when the source file is compiled with
the GCC @option{-ftest-coverage} option. It contains information to
reconstruct the basic block graphs and assign source line numbers to
blocks.
-The @file{.da} file is generated when a program containing object files
+The @file{.gcda} file is generated when a program containing object files
built with the GCC @option{-fprofile-arcs} option is executed. A
-separate @file{.da} file is created for each object file compiled with
-this option. It contains arc transition counts, and some summary
+separate @file{.gcda} file is created for each object file compiled with
+this option. It contains arc transition counts, and some summary
information.
The full details of the file format is specified in @file{gcov-io.h},
and functions provided in that header file should be used to access the
coverage files.
+
+@node Cross-profiling
+@section Data file relocation to support cross-profiling
+
+Running the program will cause profile output to be generated. For each
+source file compiled with @option{-fprofile-arcs}, an accompanying @file{.gcda}
+file will be placed in the object file directory. That implicitly requires
+running the program on the same system as it was built or having the same
+absolute directory structure on the target system. The program will try
+to create the needed directory structure, if it is not already present.
+
+To support cross-profiling, a program compiled with @option{-fprofile-arcs}
+can relocate the data files based on two environment variables:
+
+@itemize @bullet
+@item
+GCOV_PREFIX contains the prefix to add to the absolute paths
+in the object file. Prefix must be absolute as well, otherwise its
+value is ignored. The default is no prefix.
+
+@item
+GCOV_PREFIX_STRIP indicates the how many initial directory names to strip off
+the hardwired absolute paths. Default value is 0.
+
+@emph{Note:} GCOV_PREFIX_STRIP has no effect if GCOV_PREFIX is undefined, empty
+or non-absolute.
+@end itemize
+
+For example, if the object file @file{/user/build/foo.o} was built with
+@option{-fprofile-arcs}, the final executable will try to create the data file
+@file{/user/build/foo.gcda} when running on the target system. This will
+fail if the corresponding directory does not exist and it is unable to create
+it. This can be overcome by, for example, setting the environment as
+@samp{GCOV_PREFIX=/target/run} and @samp{GCOV_PREFIX_STRIP=1}. Such a
+setting will name the data file @file{/target/run/build/foo.gcda}.
+
+You must move the data files to the expected directory tree in order to
+use them for profile directed optimizations (@option{--use-profile}), or to
+use the @command{gcov} tool.
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