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The nsresult
data type is a strongly-typed enum
used to represent a value returned by an XPCOM function; these are typically error or status codes. For a list of defined result values, see Error codes returned by Mozilla APIs.
Note: On compilers that do not support strongly-typed enum
s (that is, compilers that don't support this feature of C++11), it falls back to being an unsigned 32-bit integer, as in past versions of Gecko.
Note: Prior to Gecko 19.0, nsresult
was not strongly typed. As a result, it was possible for code to misuse it, such as returning an nsresult
value from a function whose signature indicates it returns a boolean
.
Because nsresult
is strongly typed, code like the following will result in an error at compile time:
bool foo() { ... if (something) { return NS_ERROR_FAILURE; } ... }