On Thu, Nov 06, 2014 at 05:56:55PM +0100, Sylvain BERTRAND wrote: > On Thu, Nov 06, 2014 at 03:40:56PM +0000, Dimitris Papastamos wrote: > > On Thu, Nov 06, 2014 at 04:38:20PM +0100, Sylvain BERTRAND wrote: > > > On a personnal level, I port some of my C99 projects back to C89, since it > > > seems a C89 compiler is easier to write than a C99 compiler, and some > > > part of > > > my code could go in C89 only project (i.e. the linux kernel). > > > > the linux kernel is built with gnu99 iirc. > > Documentation/HOWTO: > "The kernel is written using GNU C and the GNU toolchain. While it > adheres to the ISO C89 standard, it uses a number of extensions that are > not featured in the standard. The kernel is a freestanding C > environment, with no reliance on the standard C library, so some > portions of the C standard are not supported. Arbitrary long long > divisions and floating point are not allowed. It can sometimes be > difficult to understand the assumptions the kernel has on the toolchain > and the extensions that it uses, and unfortunately there is no > definitive reference for them. Please check the gcc info pages (`info > gcc`) for some information on them."
It uses a *lot* of extensions. If I remember correctly, a significant number of gcc extensions were initially driven by the needs of linux kernel programmers. A C89 only compiler would have no hope to build the kernel in any way so I do not see how C89 is relevant here anymore.
