Problem Diagnosis
Once the cause of the error is narrowed down to a single statement within
the source code, the problem with that statement must then be identified.
Syntactical errors can generally be ruled out as a cause of failure during
run time, since such errors are almost always identified during compilation
of the application code. However, the items listed below are common causes
of run-time errors, and should be checked for failing program statements:
Logic: is the sequence of operations performed during
the processing of a message in accordance with the application design? Have
any steps been accidentally omitted?
Parameters: are the correct variable names being
used for parameters in the program statement? Do the parameter definitions
in the program statement directly match those given in the function declaration?
Pointers: do they contain valid references, and/or
have they been correctly initialized prior to the program statement?
Operating system or Presentation Manager resources:
have they been successfully allocated prior to the program statement? Are
resources released at the completion of processing for the event and if
not, is there a valid reason for retaining them?
Step #5: Diagnose the cause of the problem by carefully checking
the program statement, and correct the error.
The following sections provide descriptions of some common application problems
against which failing programs may be checked.
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