Debugging with GDB Manual The GNU Source-Level Debugger (769148-001, March 2014)
To enable us to x the bug, you should include all these things:
• The version of GDB. GDB announces it if you start with no arguments; you can also print it at
any time using show version.
Without this, we will not know whether there is any point in looking for the bug in the current
version of GDB.
• The type of machine you are using, and the operating system name and version number.
• What compiler (and its version) was used to compile the program you are debugging| e.g.
\HP92453-01 A.10.32.03 HP C Compiler". Use the what command with the pathname of
the compile command (`what /opt/ansic/bin/cc', for example) to obtain this information.
• The command arguments you gave the compiler to compile your example and observe the
bug. For example, did you use `-O'? To guarantee you will not omit something important, list
them all. A copy of the Makefile (or the output from make) is sufficient.
If we were to try to guess the arguments, we would probably guess wrong and then we might
not encounter the bug.
• A complete input script, and all necessary source files, that will reproduce the bug
• A description of what behavior you observe that you believe is incorrect. For example, \It
gets a fatal signal."
Of course, if the bug is that GDB gets a fatal signal, then we will certainly notice it. But if the
bug is incorrect output, we might not notice unless it is glaringly wrong. You might as well not
give us a chance to make a mistake.
Even if the problem you experience is a fatal signal, you should still say so explicitly. Suppose
something strange is going on, such as, your copy of GDB is out of synch, or you have
encountered a bug in the C library on your system. (This has happened!) Your copy might
crash and ours would not. If you told us to expect a crash, then when ours fails to crash, we
would know that the bug was not happening for us. If you had not told us to expect a crash,
then we would not be able to draw any conclusion from our observations.
Here are some things that are not necessary:
• A description of the envelope of the bug.
Often people who encounter a bug spend a lot of time investigating which changes to the
input file will make the bug go away and which changes will not affect it. This is often time
consuming and not very useful, because the way we will find the bug is by running a single
example under the debugger with breakpoints, not by pure deduction from a series of examples.
We recommend that you save your time for something else.
Of course, if you can find a simpler example to report instead of the original one, that is a
convenience for us. Errors in the output will be easier to spot, running under the debugger
will take less time, and so on.
However, simplification is not vital; if you do not want to do this, report the bug anyway and
send us the entire test case you used.
• A patch for the bug.
A patch for the bug does help us if it is a good one. But do not omit the necessary information,
such as the test case, on the assumption that a patch is all we need. We might see problems
with your patch and decide to x the problem another way, or we might not understand it at
all.
Sometimes with a program as complicated as GDB it is very hard to construct an example
that will make the program follow a certain path through the code. If you do not send us the
example, we will not be able to construct one, so we will not be able to verify that the bug is
fixed.
How to report bugs 277