You're right, it's described in 3.5 of http://plan9.bell-labs.com/sys/doc/compiler.html http://plan9.bell-labs.com/sys/doc/compiler.html It seems like it was

You're right, it's described in 3.5 of http://plan9.bell-labs.com/sys/doc/compiler.html http://plan9.bell-labs.com/sys/doc/compiler.html It seems like it was contemporaneous with the proposed c90 extension and also supported the = except optionally. But it was definitely something in the plan 9 compiler rather than only a gcc thing.