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GNU macro processor

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6.3 Controlling debugging output

The `-d' option to m4 controls the amount of details presented, when using the macros described in the preceding sections.

The flags following the option can be one or more of the following:

Trace all macro calls made in this invocation of m4.

Show the actual arguments in each macro call. This applies to all macro calls if the `t' flag is used, otherwise only the macros covered by calls of traceon.

Show the expansion of each macro call, if it is not void. This applies to all macro calls if the `t' flag is used, otherwise only the macros covered by calls of traceon.

Quote actual arguments and macro expansions in the display with the current quotes.

Show several trace lines for each macro call. A line is shown when the macro is seen, but before the arguments are collected; a second line when the arguments have been collected and a third line after the call has completed.

Add a unique `macro call id' to each line of the trace output. This is useful in connection with the `c' flag above.

Show the name of the current input file in each trace output line.

Show the the current input line number in each trace output line.

Print a message when a named file is found through the path search mecanism (see section 8.2 Searching for include files), giving the actual filename used.

Print a message each time the current input file is changed, giving file name and input line number.

A shorthand for all of the above flags.

If no flags are specified with the `-d' option, the default is `aeq'. The examples in the previous two sections assumed the default flags.

There is a builtin macro debugmode, which allows on-the-fly control of the debugging output format:

debugmode(opt flags)
The argument flags should be a subset of the letters listed above. As special cases, if the argument starts with a `+', the flags are added to the current debug flags, and if it starts with a `-', they are removed. If no argument is present, the debugging flags are set to zero (as if no `-d' was given), and with an empty argument the flags are reset to the default.

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