On Tue, 23 Jul 2013 at 17:58 GMT, Joe Perches [off-list ref] wrote:

Function prototypes don't need to be declared
extern in .h files.  It's assumed by the compiler
and is as unnecessary as using auto is when
declaring automatic/local variables in a block.

Since we all know this, why bother it? Having "extern" doesn't harm
readability, instead it probably helps.

...

I believe it makes grepping for extern useful as
all the matches are actual variables and structs.

You need a semantic tool.