web2c: \tracingcharsubdef
5.4.1.2 '\tracingcharsubdef': Substitution diagnostics
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To help diagnose problems with '\charsubdef', MLTeX provides a new
primitive parameter, '\tracingcharsubdef'. If positive, every use of
'\charsubdef' will be reported. This can help track down when a
character is redefined.
In addition, if the TeX parameter '\tracinglostchars' is 100 or more,
the character substitutions actually performed at '\shipout'-time will
be recorded.
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web2c: \charsubdef
web2c: MLTeX