The MySQL server and most MySQL clients are compiled with the DBUG package originally created by Fred Fish. When you have configured MySQL for debugging, this package makes it possible to get a trace file of what the program is debugging. See Section E.1.2, “Creating Trace Files”.
This section summaries the argument values that you can specify in
debug options on the command line for MySQL programs that have
been built with debugging support. For more information about
programming with the DBUG package, see the DBUG manual in the
dbug directory of MySQL source distributions.
It's best to use a recent distribution for MySQL 5.0
to get the most updated DBUG manual.
You use the debug package by invoking a program with the
--debug="..." or the -#...
option.
Most MySQL programs have a default debug string that is used if
you don't specify an option to --debug. The
default trace file is usually
/tmp/program_name.trace on Unix and
\program_name.trace on Windows.
The debug control string is a sequence of colon-separated fields as follows:
<field_1>:<field_2>:...:<field_N>
Each field consists of a mandatory flag character followed by an
optional ‘,’ and comma-separated
list of modifiers:
flag[,modifier,modifier,...,modifier]
The currently recognized flag characters are:
| Flag | Description |
d
|
Enable output from DBUG_<N> macros for the current state. May be followed by a list of keywords which selects output only for the DBUG macros with that keyword. An empty list of keywords implies output for all macros. |
D
|
Delay after each debugger output line. The argument is the number of
tenths of seconds to delay, subject to machine
capabilities. For example, -#D,20
specifies a delay of two seconds. |
f
|
Limit debugging, tracing, and profiling to the list of named functions.
Note that a null list disables all functions. The
appropriate d or t
flags must still be given; this flag only limits their
actions if they are enabled. |
F
|
Identify the source file name for each line of debug or trace output. |
i
|
Identify the process with the PID or thread ID for each line of debug or trace output. |
g
|
Enable profiling. Create a file called dbugmon.out
containing information that can be used to profile the
program. May be followed by a list of keywords that select
profiling only for the functions in that list. A null list
implies that all functions are considered. |
L
|
Identify the source file line number for each line of debug or trace output. |
n
|
Print the current function nesting depth for each line of debug or trace output. |
N
|
Number each line of debug output. |
o
|
Redirect the debugger output stream to the specified file. The default
output is stderr. |
O
|
Like o, but the file is really flushed between each
write. When needed, the file is closed and reopened
between each write. |
p
|
Limit debugger actions to specified processes. A process must be
identified with the DBUG_PROCESS macro
and match one in the list for debugger actions to occur. |
P
|
Print the current process name for each line of debug or trace output. |
r
|
When pushing a new state, do not inherit the previous state's function nesting level. Useful when the output is to start at the left margin. |
S
|
Do function _sanity(_file_,_line_) at each debugged
function until _sanity() returns
something that differs from 0. (Mostly used with
safemalloc to find memory leaks) |
t
|
Enable function call/exit trace lines. May be followed by a list (containing only one modifier) giving a numeric maximum trace level, beyond which no output occurs for either debugging or tracing macros. The default is a compile time option. |
Some examples of debug control strings that might appear on a
shell command line (the -# is typically used to
introduce a control string to an application program) are:
-#d:t -#d:f,main,subr1:F:L:t,20 -#d,input,output,files:n -#d:t:i:O,\\mysqld.trace
In MySQL, common tags to print (with the d
option) are enter, exit,
error, warning,
info, and loop.