What is C in practice?

Re:What is C in practice? by Animats on Monday June 29, 2015 @02:04PM (#9799779)

Many C programmers assume a single flat memory space. Most machines today have that. There's a long history of machines that didn't: Intel 286 in segmented mode, some Pentium variants in segmented mode beyond 4MB (Linux supports this in the kernel), IBM AS/400, Unisys Series B 36-bit word machines, Burroughs 5500/6700/Unisys Series A segmented machines where an address is a file-like path, Motorola CPUs where I/O space and memory space are distinct, and old DEC PDP-11 machines where code and data address spaces are separate. More recently, there are non shared memory multiprocessors where addresses are duplicated across processors - the PS3's Cell and many GPUs, for example.

Most programmers today will never encounter any of those.

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Re:What is C in practice? by kevin_thibedeau on Monday June 29, 2015 @08:31PM (#9802094)

There's also the assumption that null is address 0. Notably breaking the purity of C++s type system with magic 0s for 20 odd years before nullptr came along.

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Re:What is C in practice? by michaeljsmith on Tuesday June 30, 2015 @12:45AM (#9802993)

Actually the C++ spec says that 0 as a pointer doesn't actually have to have the value 0 - it just refers to a null value the same way as nullptr.

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Re:What is C in practice? by kevin_thibedeau on Tuesday June 30, 2015 @08:27AM (#9804670)

That is the point. They went through the process of tightening down the type system by invalidating automatic casts and making void* less promiscuous and then they break that whole philosophy with a magic literal "0" that can work as a normal integer or as an address placeholder for any pointer even though it won't necessarily evaluate to address zero. At that point why can't I assign "0" to a float too and enjoy some more magic there?

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