1.11 Displaying Source
The following annotation is used instead of displaying source code:
where filename is an absolute file name indicating which source
file, line is the line number within that file (where 1 is the
first line in the file), character is the character position
within the file (where 0 is the first character in the file) (for most
debug formats this will necessarily point to the beginning of a line),
middle is `middle' if addr is in the middle of the
line, or `beg' if addr is at the beginning of the line, and
addr is the address in the target program associated with the
source which is being displayed. addr is in the form `0x'
followed by one or more lowercase hex digits (note that this does not
depend on the language).