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 3 Executing the Program
 ***********************
 
 Once the program is compiled for profiling, you must run it in order to
 generate the information that 'gprof' needs.  Simply run the program as
 usual, using the normal arguments, file names, etc.  The program should
 run normally, producing the same output as usual.  It will, however, run
 somewhat slower than normal because of the time spent collecting and
 writing the profile data.
 
    The way you run the program--the arguments and input that you give
 it--may have a dramatic effect on what the profile information shows.
 The profile data will describe the parts of the program that were
 activated for the particular input you use.  For example, if the first
 command you give to your program is to quit, the profile data will show
 the time used in initialization and in cleanup, but not much else.
 
    Your program will write the profile data into a file called
 'gmon.out' just before exiting.  If there is already a file called
 'gmon.out', its contents are overwritten.  There is currently no way to
 tell the program to write the profile data under a different name, but
 you can rename the file afterwards if you are concerned that it may be
 overwritten.
 
    In order to write the 'gmon.out' file properly, your program must
 exit normally: by returning from 'main' or by calling 'exit'.  Calling
 the low-level function '_exit' does not write the profile data, and
 neither does abnormal termination due to an unhandled signal.
 
    The 'gmon.out' file is written in the program's _current working
 directory_ at the time it exits.  This means that if your program calls
 'chdir', the 'gmon.out' file will be left in the last directory your
 program 'chdir''d to.  If you don't have permission to write in this
 directory, the file is not written, and you will get an error message.
 
    Older versions of the GNU profiling library may also write a file
 called 'bb.out'.  This file, if present, contains an human-readable
 listing of the basic-block execution counts.  Unfortunately, the
 appearance of a human-readable 'bb.out' means the basic-block counts
 didn't get written into 'gmon.out'.  The Perl script 'bbconv.pl',
 included with the 'gprof' source distribution, will convert a 'bb.out'
 file into a format readable by 'gprof'.  Invoke it like this:
 
      bbconv.pl < bb.out > BH-DATA
 
    This translates the information in 'bb.out' into a form that 'gprof'
 can understand.  But you still need to tell 'gprof' about the existence
 of this translated information.  To do that, include BB-DATA on the
 'gprof' command line, _along with 'gmon.out'_, like this:
 
      gprof OPTIONS EXECUTABLE-FILE gmon.out BB-DATA [YET-MORE-PROFILE-DATA-FILES...] [> OUTFILE]
 

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