All Portfolio error codes are negative 32-bit numbers that are subdivided into multiple subcomponents. Using these components, you can identify which subsystem generated the error, and get a module-specific error number. Table 1 lists the various components of an error code:
Table 1: Error code components.
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Bit(s)|Purpose
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31 |This bit is always set. It makes all error codes
|negative numbers.
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25-30 |Object type that generated the error. This field
|identifies what generated the error: a folio, a
|device, a task, or another object type,
|generated the error. Possible values for this
|field include ER_FOLI, ER_DEVC, ER_TASK, or
|ER_LINKLIB.
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13-24 |Object ID. This is a code that uniquely
|identifies the component that generated the
|error. The value for this field is created with
|MakeErrID() and is basically two 6-bit
|characters identifying the module that caused
|the error. For example, kernel errors have an
|object ID of Kr.
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11-12 |A severity code. Possible values for this field
|include: ER_INFO, ER_WARN, ER_SEVERE, or
|ER_FATAL.
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9-10 |An environment code. This code defines who
|created the module that generated the error.
|Possible error values for this field include:
|ER_E_SSTM for system modules, ER_E_APPL for
|application modules, and ER_E_USER for user-code
|modules.
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8 |Error class. Possible error values for this
|field are: either ER_C_STND for a standard error
|code or ER_C_NSTND for a nonstandard error code.
|Standard error codes are errors that are well
|known in the system and have a default string to
|describe them. Nonstandard errors are
|module-specific and the module must provide a
|string to the system to describe the error.
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0-7 |The actual error code. The meaning of this code
|depends on the module that generated the error,
|and whether it is a standard or nonstandard
|error.
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The PrintfSysErr() kernel call accepts any error code, and prints an error string describing the error to the debugging terminal. When developing code, it is extremely useful to know why a system call is failing.
Note: Besides handling multitasking, memory management, folios, items, intertask communication, and linked lists, the kernel also handles I/O and hardware control-both topics for another section. You'll find them described in The Portfolio I/O Model."