extern sample in MSDN

Hello everyone,


I think in practical experience, extern is useful only when we have more than one compile unit (cpp file) and making cross-reference between compile units.

In the MSDN extern sample,

http://msdn2.microsoft.com/en-us/library/0603949d.aspx

It only uses one source file (compile unit) to demonstrate the usage of extern, is it correct and practical?


thanks in advance,
George

If the file is then compiled to a static library, yes.

Thanks CornedBee,


Your reply yes,

1. is it to answer the code (using extern to qualify a variable, which is define in the same compile unit) is correct?

2. Or, it is of practical usage to use extern to qualify a variable, which is define in the same compile unit.

Quote:

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Originally Posted by CornedBee

If the file is then compiled to a static library, yes.

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regards,
George

It's correct. It's even practical if it's in the same compilation unit, because included headers are part of the compilation unit. It's not really practical if it's in the same source file.

Thanks CornedBee,


"It's even practical if it's in the same compilation unit, because included headers are part of the compilation unit"

I think you mean the header file contains extern declaration and it is included in the current source file, and in the current source file there is definition of the variable, right?

In the above situation I described, what is the practical advantages?

Quote:

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Originally Posted by CornedBee

It's correct. It's even practical if it's in the same compilation unit, because included headers are part of the compilation unit. It's not really practical if it's in the same source file.

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regards,
George

Quote:

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In the above situation I described, what is the practical advantages?

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It takes up less space in the MSDN database. :)

Interesting, CornedBee. :-)


Any comments to my post #5?

Quote:

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Originally Posted by CornedBee

It takes up less space in the MSDN database. :)

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regards,
George