what's the type of stdin?

I am trying to make a rw version of popen (by returning a pair of pipes), but I am having trouble dup2'ing stdin to an end of a pipe.

Code:

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dup2(wpipe[0], stdin);

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Gives

Code:

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test.c:18: warning: passing argument 2 of ‘dup2’ makes integer from pointer without a cast

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How do I turn it into a file descriptor then? and what exactly is it?

[edit]
and

Code:

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dup2(wpipe[0], *stdin);

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gives

Quote:

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test.c:18: error: incompatible type for argument 2 of ‘dup2’

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fileno(stdin)

EDIT: But stdin is file descriptor 0, by definition.

I see. Thanks.

Quote:

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Originally Posted by cyberfish

I see. Thanks.

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As far as what type stdin is, it's equivalent to a FILE *.