[LLVMdev] MCStreamer interface

[Dale Johannesen]

On May 5, 2010, at 2:32 PMPDT, Nathan Jeffords wrote:

> 
> Global definitions like "int x;" are treated as common to allow
> linking buggy programs that forget to use "extern" on declarations.
> 
> Is this always the behavior, or only when certain options are set? This seems like a violation of the language standard.

Technically yes; the original K&R C book had the one-definition rule in it.  Early C compilers did not work this way, however, and by the time that book was published (1978) there was already a large body of code that assumed the "common" model (also Ritchie's preference, I believe).  In practice most compilers still default to this model because a lot of widely used stuff will break if they don't, and the behavior is given in J.5.11 of C99 as a common extension.

Use -fno-common to turn it off.

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