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diff --git a/gcc/doc/gcov.1 b/gcc/doc/gcov.1 new file mode 100644 index 0000000..633d754 --- /dev/null +++ b/gcc/doc/gcov.1 @@ -0,0 +1,414 @@ +.\" Automatically generated by Pod::Man version 1.1 +.\" Mon Feb 19 19:31:56 2001 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used +.\" to do unbreakable dashes and therefore won't be available. \*(C` and +.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> +.tr \(*W-|\(bv\*(Tr +.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' +.ie n \{\ +. ds -- \(*W- +. ds PI pi +. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch +. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch +. ds L" "" +. ds R" "" +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds -- \|\(em\| +. ds PI \(*p +. ds L" `` +. ds R" '' +'br\} +.\" +.\" If the F register is turned on, we'll generate index entries on stderr +.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and +.\" index entries marked with X<> in POD. Of course, you'll have to process +.\" the output yourself in some meaningful fashion. +.if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. nr % 0 +. rr F +.\} +.\" +.\" For nroff, turn off justification. 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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 (c) 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. |