21.8 Pitfalls
Macros that are given values while sendmail
processes mail might not get the value expected. If that happens,
careful hand-tracing of rule sets is required to find the
fault. For example, the value in
$g ($g) is the result of
sender address rewriting and rewriting by the rule set that is
specified in the S= equate of the selected
delivery agent. Because $g is used to define the
From: header line, errors in that line should be
traced through errors in the S=
equate's rule set.
Macros can have other macros as their values. The
sendmail program expands macros recursively. As
a consequence, prior to V8.10, unintentional loops in macro
definitions could cause sendmail to appear to
hang and to eventually segmentation-fault and core-dump. Beginning
with V8.10, such recursion is caught and the following error is
printed:
configfile: line num: expand: recursion too deep (10 max)
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