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Clarify the rule about structure typedefs being discouraged, following

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a discussion on src-committers.
This commit is contained in:
Tony Finch 2003-11-10 14:32:13 +00:00
parent 76a8862646
commit e19cd0127b
1 changed files with 12 additions and 3 deletions
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15
share/man/man9/style.9
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@ -321,9 +321,18 @@ LIST_HEAD(, foo) foohead; /* Head of global foo list. */
.Ed
.Pp
Avoid using typedefs for structure types.
This makes it impossible
for applications to use pointers to such a structure opaquely, which
is both possible and beneficial when using an ordinary struct tag.
Typedefs are problematic because they do not properly hide their
underlying type; for example you need to know if the typedef is
the structure itself or a pointer to the structure.
In addition they must be declared exactly once, whereas an
incomplete structure type can be mentioned as many times as
necessary.
Typedefs are difficult to use in stand-alone header files:
the header that defines the typedef must either be included
before the header that uses it, or by the header that uses
it (which causes namespace pollution), or there must be a
back-door mechanism for obtaining the typedef.
.Pp
When convention requires a
.Ic typedef ,
make its name match the struct tag.