Technical tips

This section describes certain problems that may arise when you use lprof and how to avoid them.

Trouble at run time

You may get no data after running a profiled program. The program terminates normally, and you receive neither a message about data being saved or an error message. This may be caused by one of three problems:

• You may not have specified -ql at both compile time and link time. If you forget to specify -ql when you link, the program will run but a data file will not be created.

• Because profiling data is saved at termination by the system call exit(2), no profiling data is saved if exit is never called. The profiled program may include a call to _exit() that is causing the program to quit without calling exit. Replace calls to _exit() with calls to exit in order to save profiling data.

• The PROFOPTS environment variable may be set to the null string.

Finally, you may see the locale's equivalent of the following error message at the end of execution:

   INFO: Dumping profiling data from process `a.out' . . .
   ERROR: Cannot find symbol table section in ./a.out.

Data File cannot be found

Occasionally, you may not be able to find the data file, despite the fact that the profiled program has terminated normally and you have received a message saying that the data file has been created.

The profiled program creates the data file in the directory in which the program is located when it terminates. If the program changes directories during execution, the data file may be created in a directory different from both the directory in
which you executed the program and the directory in which the shell is located when the program terminates.

Use the dir option of PROFOPTS to specify exactly where the data file is to be created so you will be able to find it.